The War on Bedbugs

Heat and cold treatment

2007-05-11T13:40:00.005-05:00

It's been a while since my last post, and I have to admit that I have lost the enthusiasm that I had at the beginning. I still surf the web for information on bedbugs, but am not as obsessed with them as I used to be, which may not be a bad thing after all. More and more I feel that, besides finding a solution to this epidemic, just as importantly, we need to find some ways to help us stay rational, calm, and mentally healthy. Fortunately, there is plenty of information about this that can be found on the Internet.

One strange thing that I have noticed on various bedbug blogs and forums is that, although pesticide resistance is so common, people don't talk much about it. Many sufferers don't know much about it, some are even in denial, and the experts are reluctant to talk about it since such topic is not welcome and often lead to heated argument. At least one expert told me that some bedbug sufferers took issue with her while she was trying to explain pesticide resistance to them. As a sufferer myself, I do understand that for people who have suffered so much from their infestations both financially and mentally, chemicals seem to be the last hope, therefore it is difficult for them to accept the truth that chemicals may not work as well as they have expected after all. But denying the truth will only make things worse by misleading others and spreading false information. As May Berenbaum, the head of the department of entomology at the University of Illinois, Urbana-Champaign, wrote in this article "If Malaria's the Problem, DDT's Not the Only Answer", "Overselling a chemical's capacity to solve a problem can do irretrievable harm not only by raising false hopes but by delaying the use of more effective long-term methods." (Recent research from both Virginia Tech and the University of Kentucky indicates significant pyrethroid resistance in bedbugs. Click here to see the abstract of the study done by Michael Potter and Alvaro Romero of the University of Kentuky.)

When dealing with extremely stressful situation such as a bedbug infestation, there are two things that people would commonly do. The first is to find a scapegoat, and immigrants are a convenient one, even though data clearly do not support the claim. By blaming others, one is basically implying that it isn't his/her fault, and therefore he/she does not deserve the consequence. The second is to look for a magic bullet, which is often DDT. Although subconsciously they might know that there is no such magic bullet, denying the truth would at least make them more comfortable psychologically. People talked about how DDT worked like a charm in the old days, but never mentioned that after the initial success, it failed in the Global Malaria Eradication Campaign, largely due to mosquitoes' resistance to DDT and malaria parasites' resistance to drugs. People also mentioned that the WHO was once again endorsing the use of DDT in Africa for malaria control, without realizing that its repellency action plays a large role in reducing malaria mortality, but repellency action will not do us any good in our war against bedbugs.

Besides being in denial, people also don't have enough knowledge about pesticide resistance. They don't realize that resistance occurs at the population level, and that it is very possible that one population is resistant to a pesticide while another a block away is susceptible to the same pesticide. Without knowing this, whenever they hear that an infestation has been removed by a pesticide, right away they would jump to the conclusion that bedbugs aren't resistant to that pesticide. In addition, it is possible for resistance to revert to susceptibility, and there is also cross resistance between DDT and pyrethroids. Pesticide resistance is a very complicated matter. Making the conclusion that DDT will solve our problem without having sufficient knowledge on pesticide resistance is inappropriate, to say the least. The bottom line is that, while there has been controversy over DDT's side effects on our environment and health, there has been no controversy over DDT resistance. For some background information on DDT resistance, please take a look at CDC's web site on malaria vector control.

(Updated on May 22, 07) More updates on DDT:

May Berenbaum wrote in the above mentioned article that by 1972, when the U.S. DDT ban went into effect, 19 species of mosquitoes capable of transmitting malaria, including some in Africa, were resistant to DDT. "What people aren't remembering about the history of DDT is that, in many places, it failed to eradicate malaria not because of environmentalist restrictions on its use but because it simply stopped working."

According to an article published in the Lancet in 2000, the current distribution of DDT resistance covers regions including West Africa (A gambiae), southwest Asia (Iran, Pakistan, India, Sri Lanka; A culicifacies), Greece (A sacharovi), Egypt (A pharoensis), Central America (A albimanus), and a small area of Colombia in South America (A darlingi). However, the WHO indicates in this article that recent evidence from Africa indicates that pyrethroid and DDT resistance is more widespread than anticipated.

In May 2007, the WHO clarified its position on DDT, saying that it is "very much concerned with health consequences from use of DDT" and reaffirmed its support to the Stockholm Convention and commitment to reducing reliance on DDT in malaria control.

Pesticide resistance is such a common phenomenon that it has become the biggest obstacle to the successful control of most pests. For the pests that reproduce slowly, resistance is less of a problem since it takes longer time to develop, and for some pests such as termites, resistance is not an issue, since the reproductive functions are only carried out by the king and the queen, hence no selection would occur. But for most pests, resistance is the single most critical issue we need to deal with. To see resistance in action, simply spray some cockroaches with a roach spray, and you will find how hard it is to have them killed. That is not because the sprays are not effective. These products had been tested numerous times and proved effective before released to the market. It is because the roaches have developed resistance to them after repeated use.

What many people don't realize is that, among all the causes of treatment failure, pesticide resistance is the most difficult one to deal with. If someone happens to have a resistant bedbug population at home, further treatment with the same pesticide or the same class of pesticides will do nothing but wasting more money and time, and speeding up the selection process and allowing further development of resistance. Increasing the dosage (saturation strategy) may or may not solve the problem depending on the degree of resistance, but is not practical in general. A better approach is rotating the pesticides with different modes of action. As I mentioned previously, there are a few OPs and carbamate pesticides available, along with a handful of newer pesticides and natural products. However, although experts believe that some OPs and carbamates are more effective than pyrethroids, they are not equally effective and are generally a lot more toxic, and resistance to OPs and carbamates are also common in other pests. Therefore, it is true that rotation is a good way to deal with resistance, but there is no guarantee that it will work, particularly because of the very limited choices of pesticides available to us today.

Pesticide resistance is not the only reason why we need alternative control measures. Some people are sensitive to chemicals or have little children, thus chemical treatment is not an option. Even if you do hire a PCO, he will not treat all the items that have been removed from your drawers and closets, and there are also items that cannot be treated with chemicals at all. Vikane gas fumigation and structural heat treatment are often not an option to many people since they are expensive, cannot be used to treat a single unit in a multi-family dwelling, and may not be available or legal to use in many regions. In these cases, your best bet would be some alternative control measures, such as high heat, cold and caulking. These control measures can be just as effective as chemical treatment, to say the least. If used properly, they won't cause side effects and can be done by yourself at minimal cost.

Both heat and cold have been used to treat bedbug infestations, but research and data are still scarce. Many of the following concepts and theories are general rather than bedbug-specific, but can still be applied to bedbugs.

Heat kills insects by disrupting lipids, affecting water balance, damaging cell structures, and so on. For example, under normal situation, water loss from the body surface is kept at a slow rate by the wax layer. When the critical transition temperature is reached, increased kinetic energy cause the wax molecules to break the intermolecular forces - the van der Waals forces, and move apart, which in turn allows water to escape at a faster rate and cause dehydration eventually. Heat can also denature proteins inside the insect's body. Once denatured, the protein loses its normal conformation and can no longer function properly. However, insects do develop physiological and behavioral responses to high temperature. The first line of defense is usually behavioral avoidance. For example, during structural heat treatment, as the temperature goes up, a bedbug would try to escape the heat and seek a cooler shelter. Insects also develop physiological heat tolerance. The most common mechanism is the use of heat shock proteins. When an insect is exposed to high temperature, the synthesis of normal proteins is greatly reduced, while the heat shock proteins are induced and bound to denatured proteins to prevent or repair damage caused by heat. However, heat tolerance is generally much less of a threat compared with cold tolerance. In particular, steam and boiling water are so lethal that these tolerance mechanisms become irrelevant. (Note that tolerance is commonly used to refer to insects' ability to tolerate stress caused by extreme temperatures. Tolerance occurs at the species level, whereas resistance occurs at the population level.)

Heat treatment normally refers to structural heat treatment. Super heated air is released into the target area and circulated, and the temperature is raised to 140-160^oF for several hours. This is to ensure that the temperatures in the harborages are maintained above the thermal death point, which is about 113^oF. The biggest challenge is that, unless temperature can be raised up rapidly, bedbugs would try to escape the heat by moving into deep cracks or exiting the unit being treated. Therefore, the heated air needs to be well circulated to be able to penetrate into deep cracks, and the bedbugs have to be well contained either by caulking or insecticide dust. But I highly doubt that this step is currently being taken.

Heat sensitive items such as electronics and plastics are either protected with thermal blankets or removed from the treatment area. But some items, such as vinyl windows and plastic parts of big appliances, are difficult to protect or remove and may get damaged. Depending on the temperature and the duration of the treatment, wood furniture might shrink or crack due to loss of moisture. Since not every item is treated, some bedbugs might survive if they hide in the untreated items.

Some studies have found that the combination of structural heat treatment and insecticide works better than heat or insecticide alone. For example, field trials of the combined treatment with heat and Diatomaceous Earth have been conducted in cereal processing plants in Canada and U.S.. The increased effectiveness could be due to a few factors. Heat could damage the lipid wax layer and make it easier for the Diatomaceous Earth to penetrate. Also, as a bedbug tries to seek cooler sites, increased mobility would also increase its chance of hitting the Diatomaceous Earth on the ground. This is the reason why I also believe that the combination of pyrethroid and DE would work better than either one alone. However, keep in mind that in general, insecticides have longer residual action at lower temperatures due to reduced vaporization, and that pyrethroids typically work better at lower temperatures. In some cases, heat tolerance could even provide cross protection against some pesticides, and vise versa.

Relative humidity also plays an important role in structural heat treatment. Inserts are able to lower body temperature by evaporative cooling, a mechanism that is similar to sweating. As water is released to the surface of the body and evaporates, heat energy - latent heat of evaporation is released along with it, hence the body cools down. However, if relative humidity is too high, less water will be vaporized, and hence less heat will be removed from the body. Therefore, in general, it is to our advantage to have high relative humidity during structural heat treatment. On the other hand, with low relative humidity, although an insect is able to effectively cool down its body by evaporative cooling, it loses water at a faster rate and will eventually die of desiccation. In this case, it is important to not keep any water nearby, otherwise the insect might still be able to survive.

I mentioned the use of boiling water and steam in my previous posts. The biggest advantage of using boiling water and steam is that they kill instantly on contact. (Previously I said that the temperature of boiling water was 100^oC, twice as high as the thermal death point for bedbugs, 45^oC. But this kind of comparison makes sense only when the Kelvin scale is used. Temperature expressed in Celsius or Fahrenheit is not a ratio variable since zero degree on these scales is not an absolute zero point. Nonetheless, the temperature of boiling water is much higher than the thermal death point for bedbugs, making it lethal enough to kill instantly on contact.)

While it is generally not practical to use boiling water to treat an entire infestation, it also has some advantages. There are quite a few items that can be dis-infested with boiling water:

Anything that can withstand high temperatures, such as cookware, bakeware, dishware, kitchen utensils, etc.

Anything that you decide to discard, such as furniture and vacuum bags

Small furniture such as wooden chairs and stools.

Anything that is not expensive, such as mop, broom and garbage bin. You can give them a quick rinse, and who cares if they deform a little?

Some bedding items. I used it for my sheets and blankets. But depending on the material, some items could get damaged.

For large furniture, the biggest challenge is that excess moisture can cause other problems. But if you have an effective way to remove the moisture, then you might want to consider using it.

Steam can be practically used to treat most items. Steam is about 100^oC at standard atmospheric pressure. But while it takes 1 calorie to increase the temperature of 1 gram of water by 1^oC, it requires 539 calories for 1 gram of water at 100^oC to convert to steam at the same temperature. Therefore, same amount of steam carries a lot more heat energy than same amount of boiling water does, even though the temperatures are the same, and this is the reason why steam burn is worse than boiling water burn. When steam hits a bedbug, phase transition occurs again, but in the opposite direction, namely condensation instead of vaporization, and the significant amount of heat energy is released to hit the bedbug. However, not all steam units are suited for bedbug treatment. You should choose a unit that produces steam of slow vapor flow (so that it would not blow away nymphs and eggs), low moisture and high temperature.

The problem with steam is, only a small portion of the steam will reach the target, and most of it will condense upon hitting the cool surfaces. So if you are treating a deep crack or a thick mattress, the amount of heat energy that eventually hits the bedbug may not be enough to kill. Two things can affect the amount of heat energy that hits the bedbug: the distance from the nozzle head to the surface of item being treated, and the amount of time that the steam is applied to it. Keeping the nozzle head too close to the surface or releasing too much steam to the same area might cause excess moisture. Dr. Harold Harlan suggests this distance to be around 1 - 1.5 inches. Australian Environmental Pest Managers Association recommends that the nozzle should be moved at a rate of 30cm per every 10-15 seconds. Ideally, an infrared thermometer should be used to constantly monitor the temperature. According to Dr. Stephen Kells of the University of Minnesota, the temperature of the surface just treated should be around 80^oC.

Clothes can be washed in hot water and dried on the hot cycle. A recent experiment done by University of Kentucky entomologist Dr. Michael Potter showed that washing cycle using hot water alone killed all stages of bedbugs, so did 5 minutes of drying on hot. Initially I was a little surprised by these results, but further research indicated that similar temperature and time settings were also lethal enough to kill other pests. Table 13.1 is based on the work done by Frobes & Ebeling in 1987, and shows the time required for 100% mortality (LT₁₀₀) of four common household pests.

Temp (oC)	Argentine ant (adult)	German cockroach (adult)	Confused flour beetle (adult)	Western drywood termite (nymph)
46	8.0	58	123	265
49	4.0	27	16	33
51	2.5	16	9	10
54	1.0	7	4	6

Time for 100% Mortality of Four Pests in minutes

From this chart we can see that, first, insects are very vulnerable to high temperature, probably more than most people realize, second, a slight increase in temperature can significantly reduce treatment time. For a typical dryer, the temperatures of the low, medium, and high settings are about 140, 150, and 180^oF, respectively. A five-minute drying at any of these temperatures is generally considered enough to kill all stages of bedbugs. Similarly, the temperature of the hot water at the tap is over 120^oF, and a full washing cycle is enough to dis-infest any washable items. But again, it is always a good idea to have some margin of safety.

Other equipment that can be utilized to generate high heat include microwave, oven, and steam iron. An oven probably works better than a microwave since it is difficult to monitor the temperature inside a microwave, whereas the lowest setting of an oven produces a temperature of at least 150^oF. If you live in a warm climate, you might consider wrap your items in plastic bags and place them directly under the sunlight for a few hours. Black bags are preferable since black does not reflect sunlight and hence naturally absorbs more heat than white does. However, since it is difficult to monitor the temperature of the items inside the bag, this is not a reliable way to dis-infest an item. Another alternative and probably more reliable way is keeping the items in your car that parked directly under the sunlight in the summer.

The main issues with these treatment methods include damage to the items and excess moisture. You should avoid applying heat to electronics and the outside surfaces of your furniture, and be very careful with the items that have plastic or adhesives. Both boiling water and steam could cause excess moisture. But in my opinion, moisture is a small price to pay, and it can always be removed or reduced afterwards with fan, dehumidifier, paper towel, hair dryer, and so on.

Cold treatment can be used to treat the items that are difficult to treat otherwise. Cold too can cause protein denaturation as well as irreversible injury to the cell structures and the neuromuscular system. However, cold treatment is generally less effective than heat, and cold tolerance poses a greater threat than heat tolerance does. You might wonder how an insect, about 70% of whose body is water, can survive sub-zero temperatures for hours or even days. There are a few reasons behind this. Firstly, the insect body might contain high concentration of antifreeze proteins and cryoprotectants such as glycerol, which allows the insect to depress the freezing point of the body fluid well below the freezing point for water. Secondly, even when the freezing point is reached, an insect might have the ability to undergo a process called supercooling, so that the body fluid does not freeze even when the temperature falls well below the freezing point. In fact, pure water, which consists of hydrogen and oxygen only, can be supercooled to about -42^oC. While natural water, which contains other substances such as minerals, dissolved gases, and organic and inorganic substances, freezes at 0^oC. These substances act as the nucleation agents, around which ice crystals start to form and spread, and the process is termed heterogeneous nucleation. But since pure water does not have such substances, nucleation occurs spontaneously once the supercooling point is reached, and the process is termed homogeneous nucleation. Nucleation and the subsequent crystal growth are the two essential steps of crystallization - a process that converts a liquid to solid crystal.

The presence of any nucleation agent or ice crystals can be devastating to an insect that undergoes supercooling, since once ice crystal starts to form, it can spread rapidly. To avoid such danger, an insect must try to minimize the water content in the body and to avoid any contact with external ice. In addition, supercooling is often associated with diapause, a predictive dormancy during which metabolic rate is greatly reduced and development is suspended. Before entering diapause, an insect would empty its gut to remove any potential nucleation agents. The bedbug's ability to survive without feeding for more than a year and to withstand subzero temperatures for extended period of time largely owes to its dormancy mechanism. There are two types of dormancy: predictive and consequential. Consequential dormancy is usually an immediate response to harsh environmental conditions such as extreme temperatures and dehydration, whereas predictive dormancy is predetermined. For example, the shortening of the day length signals the arrival of winter and could trigger diapause. But due to the use of air conditioning and heating and consequently the relatively constant indoor temperature, personally I think the importance of diapause is not as significant as it was in the old days, and dormancy is most likely consequential and is caused by adverse conditions such as lack of food or pesticide application.

To combat these mechanisms, researchers have discovered ice nucleating active bacteria that can be used to initiate nucleation and reduce insect cold tolerance. However, some freezing tolerant insect species have developed a complete different mechanism and can withstand certain amount of freezing outside the cells, and deliberately promote crystallization at higher temperatures to prevent the injury or death caused by rapid and spontaneous crystallization. Personally I doubt that household pests such as bedbugs would have evolved such extreme cold tolerance mechanism, even though they did live in the caves with humans in the ancient times. But this is just my opinion and is not based on scientific facts.

There are different opinions on the temperature and time settings for cold treatment. Some experts have suggested that 0^oF for about one week should be able to kill all life stages of bedbugs. But since very few experiments have been done on cold treatment, I don't think this is conclusive and would only take it as a minimum requirement. For your information, a home refrigerator usually runs a few degrees above 0^oC and a home freezer runs between -15 to -20^oC.

Nevertheless, cold treatment can be used to treat many items that can't be treated with chemical or heat, such as toys and books. Small items can be placed in the freezer compartment of your refrigerator. For bigger items, use a chest freezer. However I've found that in a chest freezer, the temperature was acceptable at the bottom, but was much higher near the top, so do not over-pack the freezer. Unless you have a commercial unit, it is generally not practical to treat furniture with cold. But if you live in a cold climate, you might be able to dis-infest your furniture by wrapping them in plastic sheets and keeping them in your balcony or backyard for a few weeks in the winter.

Electronics seem to be the most difficult to deal with. Aerosols might cause short-circuit, and heat can damage the electronic circuits. Electronic components operate properly within the commercial temperature range of 0^oC - 70^oC, and could get damaged at sub-zero temperatures. I did keep many small electronic devices such as router, telephone, answering machine, mouse and keyboard in the freezer for over a week before moving, and everything still worked fine afterwards. My suggestion is, if it is something that you can part with and there is no other option, consider cold treatment, but if it is something expensive, don't take the chance. Also, after you take the item out, don't power it up immediately, instead, let it warm up slowly and reach the room temperature first.

Whether you use heat or cold, ideally you want to have the temperature changed as rapidly as possible, so that injury can be caused before the tolerance mechanism is turned on. Never expose an item to an intermediate temperature before exposing it to a more severe temperature. An insect's tolerance mechanism is turned on once a threshold is reached, and sometimes this could happen in a matter of a few minutes. Once the mechanism is turned on, it will provide protection from injury at a more severe temperature, and the effectiveness of treatment will be greatly reduced. One strategy to fight such mechanism is to keep repeating the cycle of freezing and thawing. This is because as the temperature returns to normal, the tolerance mechanism will be turned off as well. However, insects have developed a variety of tolerance mechanisms, some are associated with great fitness cost and must be turn off quickly while others take much longer to turn off. Since temperature setting and timing can be quite different for different insect species, without further research on the effects of cold treatment on bedbugs, it is difficult to employ this strategy practically. To minimize moisture caused by condensation, it is recommended to keep the items in a polyethylene bag, remove as much air out as possible, and thaw slowly after the bag is taken out of the freezer. When treating books with cold, another technique is to insert some aluminum foil sheets in the book to increase the freezing rate, probably due to aluminum's good thermal conductivity.

Similar to Integrated Pest Management itself, the use of extreme temperature is often mistakenly believed to be a new approach to pest control and not commonly accepted and practiced. The truth is that, the use of both heat and cold can be traced back to the beginning of pest control, but has declined since the arrival of the synthetic pesticides. However, due to the side effects and resistance that synthetic pesticides cause, there has been renewed interest in the use of heat and cold. Insects do develop physiological and behavioral responses to heat or cold. But a few degrees increase in temperature can be more significant than one hundred fold increase in pesticide dosage. And such increase in temperature or duration of cold/heat treatment is usually safe and doable, whereas such increase in the dosage of a pesticide could cause significant consequences and is usually not practical. It is true that heat or cold treatment does not have residual effects and treatment has to been done very thoroughly. But given the low effectiveness of the residual pesticides currently available, thorough treatment is likely the only way to effectively eliminate an infestation.

Updated on Jan 03, 2008.

It's been over a year since I had my bedbug infestation and subsequently infested my parents' place, and I believe I can finally claim victory now. I have stopped posting simply because I don't have much to write about anymore. If you work hard enough, it is entirely possible to win your own battle, but overall, we are losing this war, and I don't see an end to it yet. Bedbugs are still spreading everywhere and there is still no magic bullet.

Here are a few more recommendations that I would like to make:

Make notes of what you do everyday. By doing so you will know what you have done and will be able to identify easily what steps you might have missed.

Use plastic bags for storage. Ziplock bags are preferred. Keep the items that you don't use daily in a plastic bag before putting them in a drawer. Discard all the cardboard boxes. If you can't, place each box inside a garbage bag.

Use plastic sheets since bedbugs have difficulty crawling on them. Keep a plastic sheet under your CPU to prevent bedbugs from crawling into it, and under your chair, couch, and bed for extra protection.

"Bugged Out in Brooklyn" made a great suggestion on one of my old posts, which was to wrap double sided carpet tape along the side of the mattress over a fitted sheet. This should work well provided that there is enough space between the mattress and the bed frame so that they don't touch each other.

If everything else fails, the bed sheet can be used as your last line of defense. If you can somehow attach a piece of plastic sheet to the edges of the bed sheet, bedbugs will have a hard time getting close to you. You can even use this when you stay in a hotel. For extra security, have some double sided carpet tape on top of the plastic sheet. This way even if the bedbugs drop from the ceiling, they will be trapped. For this to work properly, the head and the foot of the bed should not be significantly higher than the mattress, otherwise you will need a very long sheet to cover the head and the foot of the bed.

Updated on May 15, 2008

Yes, I stopped posting, since I had posted everything that I knew about bedbugs. This blog is not perfect, but I think it is informative, and if you try as hard as I did, I believe you will have the success as well.

Currently I spend lots of time meditating, although this has nothing to do with bedbugs, I do believe that meditation is one of the most effective ways to deal with the stress caused by bedbug problem. I am going to a meditation retreat this summer, due to the success that I had previously, I am not so afraid of bedbugs anymore, but honestly, I am still a bit worried that I might get them again from the retreat.

Updated on Nov 20, 2009

It’s been three years since I first encountered bed bugs, and I remain bed bug free. I don’t have anything new to write about, but I do want to stress again that I am not against using pesticides. I won’t hesitate to use anything that’s effective on bed bugs, even if it could cause side effects to my health and/or the environment. But the truth is, most pesticides available are simply ineffective but costly. This is the reason why I recommend other measures such as caulking and heat treatment.

Also, any advertisement in the comment section will be removed. I’ve been trying to keep this blog ad-free from day one, because I believe this is the only way to keep my views unbiased.

Someone posted in the comment section his/her experience of eradicating bed bugs using space heaters, which I think is worth reading. Heat is one of the most effective measures against many insects including bed bugs.

There have been too many spam comments so I turned on moderation, sorry for the inconvenience.

Tracing the cause of the bedbug epidemic

2007-03-19T11:46:00.000-05:00

First off, I don't want to give you the impression that I will be providing you with the exact explanation for the recent resurgence of bedbugs. If that's what you are looking for, then the quick answer is, no one knows for sure. Many factors have been suggested as the causes of this bedbug epidemic, such as an increase in immigration and international travel, the banning of many powerful pesticides, changes in pest control practices, little awareness and knowledge of and limited experience in controlling this pest, and pesticide resistance. But none of these has been scientifically proven. Although I don't have an exact answer myself, I will be trying to discuss some of these factors in some depth and hopefully that will help you reach your own conclusion. A few web sites also suggest that terrorists are behind this epidemic since it started roughly at the same time when 9.11 happened, but such speculation won't get us anywhere without any hard evidence, so I am going to skip that.

To identify the cause of this epidemic, the first thing to do is to find the statistics on the number of infestations and the time when they occurred. Unfortunately, they are very scarce. The most well-known figures are the number of complaints received by the city of New York and the city of Toronto, and the 70% increase in bedbug reports from 2000 to 2005, according to the National Pest Management Association (NPMA). But the figures given by the NPMA seem to be self-conflicting to me. According to this report in USA Today, "the National Pest Management Association says bedbug reports increased 71% from 2000 to 2005, with member companies that had received one or two calls a year now logging 10 to 50 a week." An increase from one or two calls a year to 10 to 50 a week is obviously much greater than 71%, no wonder some other reports suggested a 50-fold increase based on the same figures given by the NPMA. Nevertheless, I have also found some more data supplied by a few pest control companies. Based on all these numbers, I would guess that, the number of infestations started to pick up around 1999, then sometime between 2001 and 2003, it started to grow exponentially.

Although it is almost beyond doubt that some bedbugs have been brought into the United States from overseas, it does not explain the sudden explosion in bedbug populations. Throughout the entire American history, immigrants have been coming to this country and have been a major source of population growth, why are they suddenly causing this bedbug epidemic now? Nobugsonme, who runs the Bedbugger blog, also wrote an article on this subject with a focus on New York City, and asked the same question.

According to this news article on National Geographic's web site, no single tropical bedbug (Cimex hemipterus) was found in England based on surveys carried out by biologist Clive Boase of the Pest Management Consultancy in UK. Boase suggested that if international travel were the origin of the problem, he would "expect tropical bedbugs to be turning up alongside the better known temperate bedbugs." As far as I know, the bedbugs that have been found in Australia, Canada, and U.S. are also overwhelmingly temperate bedbugs (Cimex lectularius), but I'm not going to make any conclusion here since I don't have the data to back me up. Just for your information, the common bedbug is normally found in the northern temperate climates of North America, Europe, and Central Asia, whereas the tropical bedbug is limited to tropical and semi-tropical regions including Florida. According to the University of Florida's Department of Entomology and Nematology web site, these two species of bedbugs can be distinguished by looking at the first segment of the thorax. "The prothorax of the common bed bug is more expanded laterally and the extreme margins are more flattened than that of the tropical bed bug".

Statistics on immigration and international travel also do not support the claim that they are the causes of this bedbug epidemic. Table 12.1 shows the number of persons that obtained permanent resident status between 1996 and 2005. The only significant increase occurred in the period 2000-2001 and the period 2004-2005, but only after several consecutive years of decline. If you compare the numbers from 1996 and 2001, the increase was only 15% in six years, or 3% annually. Similarly, the increase from 2001 to 2005 was merely 6%, or 1.5% annually. Overall, except for the 11% increase in the 1950s and the decline in the first three decades, annualized immigration growth rates were mostly between 2% and 5% throughout the last century. For the period 2000-2005, the average number of immigrants per year actually dropped slightly to 957 thousand, from 977 thousand for the period 1990-1999. Since some people may argue that bedbugs mainly existed in the developing countries before this epidemic, I refined the calculation by subtracting the numbers from Western Europe, Canada, Australia, and New Zealand from the total. The growth rates did go up by a few percentage points from the 1940s to the 1980s, but did not change since the 1990s, and the overall pattern remains the same.

year	1996	1997	1998	1999	2000
# of immigrants	915,560	797,847	653,206	644,787	841,002
% increase	n/a	-13%	-18%	-1%	30%

year	2001	2002	2003	2004	2005
# of immigrants	1,058,902	1,059,356	703,542	957,883	1,122,373
% increase	26%	0%	-34%	36%	17%

Table 12.1 persons obtaining legal permanent resident status (1996 - 2005)
source: 2005 Yearbook of Immigration Statistics

Besides immigrants, the United States also takes in refugees every year, but the number is much smaller (less than 100 thousand a year on average), and thus was not taken into account.

The number of immigrants is just a drop in the bucket compared with the number of international travelers. According to my calculation based on the statistics for the last ten years, on average, the number of international travelers (inbound and outbound combined) was over 100 times as many as the number of immigrants, with the outbound travelers outnumbering inbound travelers slightly. Table 12.2 shows the number of international travelers for the period 1998-2005 (earlier data are not available). Again, there was no significant increase in the number of international travelers during this whole 18-year period. On the contrary, the annualized growth rates were 3.2% and 1.5% for the periods 1988-1996 and 1997-2005, respectively, indicating a decline in growth during the time when this epidemic started.

year	1988	1989	1990	1991	1992	1993	1994	1995	1996
# of vistors	74,611	77,503	83,986	84,240	91,159	90,190	91,203	94,081	98,800
% increase	n/a	4%	8%	0%	8%	-1%	1%	3%	5%

year	1997	1998	1999	2000	2001	2002	2003	2004	2005
# of vistors	101,104	102,075	105,731	112,565	106,369	101,647	97,468	107,894	112,711
% increase	2%	1%	4%	6%	-6%	-4%	-4%	11%	4%

Table 12.2 international travelers (1988 - 2005)
numbers in thousands, inbound and outbound combined
source: Office of Travel & Tourism Industries

It also depends on how you look at it. If you believe that all the bedbugs in this country have been brought in from overseas, then you would expect to see a spike in the number of immigrants and international travelers, but the data clearly indicate otherwise. In particular, both tables show a significant decline in immigration and international travel after 9.11, while the number of bedbug infestations surged during the same period. But if you believe that a few bedbugs have been brought into this country and have multiplied, then you should know that, contrary to common belief, bedbugs have never been completely eradicated in the U.S., and that based on the rate at which they are spreading right now, all other conditions being equal, this epidemic should have started many years ago. It should also be noted that on average, outbound visitors actually outnumber inbound visitors, meaning that while many people come to the United State, U.S. residents also go abroad for various reasons. Furthermore, don't forget the vast amount of U.S. troops deployed overseas. This number has been over half a million on average since the end of World War II (a total of 27.3 million billets during 1950-2000), and the troops often operate in areas with serious insect-transmitted diseases, let alone some bedbugs. Isolation of a bed is no easy task, isolation of a country is simply not feasible.

A more convincing explanation is the change in pest control techniques. We know that bedbugs were largely eliminated by the use of DDT. But bedbugs weren't the target pests, other pests such as cockroaches were. However, although bedbugs were largely eliminated by DDT, cockroaches, or German cockroaches to be specific, developed strong resistance to DDT within a decade and survived (does this suggest that cockroaches are more hardy and resilient than bedbugs?). Even though DDT was banned, baseboard treatment with residual pesticides such as organophosphates, carbamates and pyrethroids became a standard procedure for cockroach control. Because of this practice, it's believed that the bedbugs that had been brought into someone's home accidentally often got killed before they could establish an infestation. In the meantime, the roaches developed resistance to every insecticide used, until the early 1980s, when hydramethylnon bait was introduced to fight these hard-beaten bugs. The bait achieved much greater results than expected, largely due to its secondary killing effect. Once a roach feeds on a bait and dies, the lethal doses would remain in the feces and carcass, which would be fed upon by other roaches in the harborage (Interestingly, many common cockroach species including German cockroaches have all been found to eat one another). Because of the high effectiveness of the baits, according to Dr. Phil Koehler, an entomologist at the University of Florida, the pest control industry began to switch from baseboard treatment to the use of baits and IGRs in the early 1990s, and sprays have been practically eliminated by 1995, a few years before this bedbug epidemic started. Although the German cockroaches have yet developed resistance to hydramethylnon, a recent research from the University Of Florida indicated that about 60% of the German cockroaches refused to east most commercial baits. This just shows how adaptive these pests are.

Another reasonable explanation is the cancellation and restriction of many powerful pesticides. We all know that DDT was banned on Jan 1, 1973. But many more pesticides have been banned or heavily restricted during the past few decades. Some of them are believed to be more effective than the pesticides available today.

The first powerful but also the most notorious class of pesticides is the organochlorines, which include DDT, aldrin, chlordane, endrin, endosulfan, dicofol, etc. The modes of action of most of these pesticides are not clearly understood. They are generally broad spectrum, relatively low in toxicity to mammals, but persist in the environment long after application and in organisms long after exposure, which is the main reason why most of them have been banned. A few of them are still being used today. For example, lindane was recently banned by the EPA for all agricultural uses, but is still being used for the treatment of headlice and scabies.

The second class is the organophosphates (OPs), which include parathion, malathion, diazinon, dichlorvos, chlorpyrifos, etc. They bind to an enzyme in the synapse called acetylcholinesterase that is responsible for breaking down acetylcholine after it has carried its message across the synapse, which results in repetitive stimulation of the nerve. The over-stimulation of the nervous system eventually causes the insect to die (DDT and pyrethroids also cause over-stimulation of the nervous system, but through different mechanisms). Although OPs degrade much faster than organochlorines, they have much greater acute toxicity, mainly because humans also use acetylcholine as a neurotransmitter and acetylcholinesterase to break it down. When the Food Quality Protection Act was first signed into law in 1996, 49 OP pesticides were registered for use in pest control. By the end of the EPA's 10-year review period, seventeen of them including the popular household pesticides diazinon and chlorpyrifos had been cancelled or heavily restricted. For diazinon, retail sales for indoor household use stopped by the end of 2002. For chlorpyrifos, all sales to consumers stopped by the end of 2001.

The third class is the carbamates, which includes carbofuran, aldicarb, carbaryl, bendiocarb, propoxur, etc. Like organophosphates, carbamates are also acetylcholine esterase inhibitors. The difference is that organophosphates are irreversible inhibitors, meaning that they do not release the bound cholinesterase and recovery depends on the new cholinesterase produced by the body, whereas carbamates are reversible inhibitors. Carbamates generally degrade faster and are less toxic than organochlorines, although some of them can be just as lethal. The EPA has already proposed the ban on carbofuran, and is finishing the re-assessment on aldicarb.

My own search for insecticides registered and intended for bedbug control has turned up these results:
- Organochlolines: no product has been found
- Organophosphates: there are 341 products, but most have been cancelled, only 24 products are available with the active ingredient being either malathion or DDVP (dichlorvos).
- Carbamates: there are 266 products, only 76 are still available with the active ingredient being carbaryl.

According to this article on CDC web site, apparently two carbamates - bendiocarb and propoxur, have also been used to treat bedbug infestations in Toronto. Although the EPA registration of bendiocarb has been voluntarily cancelled by the registrants, the registration status of propoxur is still active, but I failed to find any products intended for bedbug control. I cannot guarantee the accuracy of these search results, but it should give you an idea how many pesticides we have lost in the past few decades.

With most of the pesticides in these three classes phased out, what's left is a class of pesticides that is supposedly almost perfect, i.e., pyrethroids, due to its quick acting, relatively low toxic to mammals, and less persistent in the environment. However, experts believe that pyrethroids are less effective than many organophosphates and carbamates, and are even repellent to bedbugs (although a recent research indicated otherwise). More importantly, whenever a pesticide or a class of pesticides is being heavily relied upon, one thing is bound to happen - pesticide resistance. In my opinion, if pyrethroid resistance is not already the biggest obstacle we are facing now, it will soon be.

Some people believe that before this bedbug epidemic, while bedbugs were non-existent in this country, they were common in the developing countries. This is simply another myth and misconception. As nobugsonme questioned in her another article, "If DDT more or less eliminated bed bugs in the USA, but they still flourished overseas, why has it taken about 30 years for them to come back?" One thing is almost certain, with the affordability and accessibility of many powerful pesticides, just like malaria, bedbugs were largely eliminated not only from this country, but also from many other regions of the world including many developing countries. Given that bedbugs are such good hitchhikers and that so many people are visiting or returning to U.S. everyday (currently, there are over 100 million international travelers per year, or over a quarter of a million per day), if bedbugs were common in other parts of the world, this epidemic would have happened many years ago and would have been much worse than it is now. Under the pressure from U.S. and E.U., many developing countries have also banned many powerful pesticides, particularly the organochlorines in the past. In 2001, more than 90 countries signed the Stockholm Convention on POPs, and agreed to reduce or eliminate the production, use, and/or release of 12 key Persistent Orgainc Pollutants (POPs), which included nine organochlorine pesticides. Could the banning of these pesticides have also resulted in a resurgence of bedbug infestations in these countries, which in turn brought more bedbugs into this country? If it has happened here, I don't see why it can't happen elsewhere.

Many people also believe that bedbugs were completely eradicated in the U.S. and other developed countries by DDT. This is not true either. Most experts agree that, although rare, bedbug infestations have always existed in this country. Dr. George Rotramel, a pest management consultant and a professor at the University of Illinois-Chicago took one step further and suggested something different in his article "What Caused the Explosion in Bed Bug Populations?"

"Bed bugs were immediately investigated as potential vectors when Acquired Immune Deficiency Syndrome (AIDS) first appeared in the early 1980s. These studies would not have been conducted unless the Centers for Disease Control and Prevention (CDC) and other health experts knew that bed bugs were common in parts of San Francisco and other major cities."

I don't know if there are statistics that support Dr. Rotramel's theory, but given the secretive behavior of bedbugs and the fact that many people do not react to the bites, this is not entirely impossible.

Due to the fact that so many factors may be involved and that so many changes have taken place, amazingly, all within the last five to ten years, it is almost impossible to know what exactly has caused this bedbug epidemic. "The bottom line is it may be a convergence of all those factors, but none of that really explains the rapid increase in recent years," said Michael Potter, a professor and urban entomologist at the University of Kentucky.

Correcting some mistakes and revisiting my strategy

2007-03-07T07:59:00.000-05:00

When I first started this Blog, I never expected that I would spend so much time on it. Since the support and information that I received from others helped me tremendously during the worst period of my ordeal, I figured that maybe it was my turn to help others by writing down some of my experience and knowledge. But somewhere along the line I noticed that some people were so desperate that they would blindly follow any advice given by others without hesitation, which made me quite nervous because any inaccurate information could potentially cause adverse effects. This is the reason why I have gradually got into the habit of doing research before writing my Blog or giving advice to others. And this is also the reason why I often appear to be challenging others', including the experts' views, even though I may not be always correct. Since apparently we still have very limited knowledge about bedbugs, I think it should be agreed that what's important is not to argue who is right or wrong, but to find the accurate information, reach the correct conclusion, and find the best way to defeat the bedbugs.

Although I have been trying hard to ensure the accuracy of the information that I give to others, mistakes still happen. Some of the mistakes that I have made in my previous articles include that,

- I mentioned that all pesticides registered before 1984 were required to be re-registered under the Pesticide Registration Improvement Act. This was a mistake since this legislation only established pesticide registration services fees. It's the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) that requires the EPA to review the pesticides registered prior to Nov 1984 to ensure they meet current scientific and regulatory standards. All registered pesticides also must meet the safety standard of the Food Quality Protection Act (FQPA). It's the FQPA that has resulted in the cancellation or restriction of many organophosphate and carbamate pesticides, some of which are believed to be more effective than pyrethoids in controlling bedbugs. The cancellation and restriction of these pesticides are likely one of the several main factors that have led to the recent resurgence of bedbugs.

- I cited combined pyrethroid and carbamate two-in-one treated bed nets as an example of tank-mixing, and suggested that it might not be the best approach since both pyrethroid and carbamate affect the nervous system. Although this is not wrong, strictly speaking, this strategy may not be considered as tank-mixing, since pyrethroid and carbamate are not mixed, but rather are applied to different parts of a bed net. The typical tank-mixing strategy would actually mix two or more pesticides, which could have some undesirable consequences such as incompatibility between pesticides, and reduced overall effectiveness if one of the tank-mixing partners has any repellency action. But I don't think that there is a specific term for applying multiple pesticides at the same time without mixing them. Furthermore, although it is true that both pyrethroids and carbamates affect the nervous system, resistance to pyrethroids is mainly caused by sodium channel gene mutations, whereas carbamates work by binding to an enzyme in the synapse called acetylcholinesterase, or simply put, they have different site of action than pyrethroids do, therefore, it does make sense to rotate or combine these two classes of pesticides.

- I also suggested that insects would try to avoid chemicals in general. This too may not be accurate. It may be possible for some chemicals to have very low repellency to certain insects, because, firstly, although behavioral resistance is common, it takes time to develop, secondly, if the insect population has already developed high degree of physiological resistance, then it may not be necessary to develop behavioral resistance. Correct me if I am wrong here, but my thinking is that, an insect population that has developed behavioral resistance to an insecticide would have less exposure to it, which would lead to reduced selection pressure, and would in turn delay the development of physiological resistance, and vice versa. Although behavioral resistance may be less important than physiological resistance, it seems to be more complicated.

With all due respect to the experts on bedbugs in different fields, I think it's also important to realize that even the experts may make mistakes from time to time, since everyone only specializes in one or several fields. The only know-it-all expert is probably the web, although it also contains misinformation. In my opinion, the bedbug sufferers are also the experts, since they live with bedbugs everyday and they live with the real bedbugs (I call them real bedbugs because researchers often work with lab strain bedbugs, which can be quite different than field strain ones in many aspects), they know a lot of things that the experts may not know. For example, Parakeets, a Yahoo Bedbugger Group member, once gave me very detailed answer to my question about bloodstains on pillow and sheet, that I considered very valuable and that I didn't think the experts could provide, since they simply didn't get bitten everyday. Also, we know that thoroughness is the key to successful treatment of many pests. Some responsible and experienced PCOs know how and where to find the harborage sites. But this is you home, you live in it everyday whereas a PCO will only spend from a few minutes to several hours on a treatment job, depending on the size of your residence as well as his work ethic. There might be some hidden cracks and crevices that you know of but the PCOs may easily miss. My point is that, while it's necessary to follow experts' advice, it is also important to use your own judgement.

Similarly, last time I suggested caulking as an important alternative control measure, and in fact it has been recommended by quite a few experts as a long term control measure, and believe it or not, some pest control companies even provide caulking and sealing as an add-on service. But it does not necessarily mean that caulking is the only solution to our problem. There are many, many smart people out there, and sometimes all it takes is just one smart idea to have a tough problem solved. I also mentioned the use of boiling water in my last article, but it does not mean that you should start pouring it on everything, since it can potentially harm yourself, damage the item, and lead to other problems such as dust mite and mold growth, and provide hospitable environment to many pests. Again, whether you take advice from an expert or from an amateur like me, it is important to use your own judgement.

I've already discussed the causes of failure of extermination in my previous article, but I would like to get into more details this time.

The failure of a treatment can be caused by a number of factors, and here are a few common ones:

1. The eggs survived the treatment and hatched afterwards.

2. The PCO did not do a thorough job and missed some harborage sites.

3. Some bedbugs were hiding in wall voids during the treatment and survived.

4. Your neighbors also had bedbugs, which invaded your home after treatment and caused re-infestation.

5. The bedbugs were resistant to the pesticide used.

Let's take a look at them one by one.

1. The eggs survived the treatment and hatched afterwards

We know that with a few exceptions, insecticides are not capable of killing eggs since they are protected by eggshells from mechanical injury, desiccation, as well as insecticide application, and this is the reason why eggs can often survive treatment. Although I always suggest that one of the best ways to prevent egg-laying is to cut off the food supply by protecting ourselves, it may be difficult for some people to do so effectively, in which case it becomes necessary to repeat treatment. A few experts have suggested repeating treatment every two weeks until the bedbugs are gone. My question then is, if eggs hatch in two weeks, why don't the hatchling bedbugs get killed by the residual effect of the insecticide? And why is it necessary to repeat treatment every two weeks instead of one, or three weeks?

I believe that the failure of residual control can be caused by one or several of the following reasons.

The length of the residual control is too short.

The bedbugs did not come into contact with the pesticide, either because the PCO did not apply the insecticide to the areas en route to where bedbugs live or feed, or the bedbugs avoided the insecticide, whether intentionally or not.

The bedbugs were resistant to the insecticide applied.

Most residual insecticides for bedbugs have three months of residual control according to the labels, but it could be a lot shorter in reality. The length of residual action depends on many factors, such as the dosage applied, the type of surface treated, temperature and humidity, and the presence of dirt and dust on the surface. But for pyrethroids, researchers have discovered that the UV rays in sunlight are the primary cause of breakdown. Pyrethroids may break down in a matter of several hours under direct sunlight, but can persist for months in areas with limited sunlight. Under normal situation, they last from a few days to several weeks, although different generations of pyrethroids can have different lengths of residual action. Harvard University Operations Services web site also suggests that most residual insecticides last for one month. So I guess it's safe to say that, for indoor application, the residual action of pyrethroids lasts from a few weeks to a month under normal circumstances.

If the above hypothesis is valid, then the failure of residual control is likely due to the bedbugs' avoidance of or resistance to the insecticide. Either way, I think it's safe to conclude that residual action is not a guaranteed way to eliminate the bedbugs.

To find the answer to my second question, I compared the data from 20 sources. The data are mostly from the entomology web site of some major universities, since I believe that universities not only have the most talented people, but also provide the most unbiased information. Other sources include some most reputable experts on bedbugs such as Dr. Harold Harlan and Cooper Pest Solutions.

These are the sources that I used in case you want to do your own investigation, all links are valid as of the time of writing:

University of Kentucky, Virginia Tech, Harvard University, University of Sydney, Cornell University, University of Florida, Pennsylvania State University, Institue of Clinical Pathology and Medical Research (PDF), Utah State University (PDF), Ohio State University, University of Arizona, North Carolina State University, Purdue University, University of Minnesota, Health Canada, WHO (PDF), Michigan Department of Community Health (PDF), The Best Control II (PDF), Armed Forces (by Dr. Harold Harlan), Cooper Pest Solutions

Here are the things that I can see from these data:

- The hatching time (incubation period) is temperature dependant, and most sources agree that it takes 6 to 17 days, or one to three weeks, to hatch at room temperature (above 21^oC), and up to 28 days at lower temperatures. Eggs are not laid at temperatures lower than 50^oF.

- The development time depends on both temperature and food supply. There seems to be more disagreement on the exact length of the development time. Most sources indicate that under ideal conditions, bedbugs can complete development in one or two months. Dr. Harold Harlan suggests that a full cycle (from egg to egg) could take as little as five weeks to complete at a temperature between 28^oC and 32^oC, and a relative humidity between 75% and 80%. Ohio State University Extension's web site suggests 21 days at 86^oF, and 120 days at 65^oF. Considering that our room temperatures are a few degrees lower than the ideal temperature range and that bedbugs normally have 3 to 4 generations a year, I would say that under normal conditions, the total development time is at least 2 to 3 months. (Note that some of these sources give the full egg-to-adult development time, while others give the length of the nympal period instead.)

- Although the numbers are from some most reliable sources on the Internet, they are quite different from each other, particularly on the development time, and I don't know how many of them have been obtained through independent research. At the time of writing, Wikipedia, the free encyclopedia written by volunteers and apparently one of the most popular information sources on bedbugs, also states that "the eggs hatch in one to two weeks", and that "at room temperature, it takes about 5 weeks for a bedbug to pass from hatching, through the stages, to maturity", which obviously differs from the numbers provided by most experts. This just shows how little we know about bedbugs at this point and how easily mistakes can be made.

If egg-hatching is the only cause of treatment failure, then the best time to re-treat should be after all eggs have hatched and before any nymph reaches maturity, which is about three weeks after the first treatment, based on the arguments above. But if other factors are involved, for example, if some adult bedbugs have survived the treatment, than it may be necessary to repeat treatment at a shorter interval.

2. The PCO did not do a thorough job and missed some harborage sites.

Although it is easy to miss a few harborage sites during treatment, if you keep seeing bedbugs or getting bitten after treatment, and if you have done thorough preparation, especially have eliminated the clutters before treatment, then it is possible that your PCO did not do a good job (it is also possible that the bedbugs were resistant to the insecticide applied). As we have concluded above, residual control is not guaranteed to eliminate these survivors, and even if they do get killed, they may lay eggs, which will even survive the next treatment. Thoroughness is the key to the success of a treatment, if your PCO cannot do a thorough job, consider switching to a better PCO.

3. Some bedbugs were hiding in wall voids during the treatment and survived.

Whether your PCO use chemical treatment or structural heat treatment, it is possible to cause the bedbugs to disperse to other rooms of your home or even your neighbors' homes. You definitely don't want this to happen since the matter will be out of your control and the bedbugs can come back to haunt you again in the future. Some PCOs apply insecticide dust along the baseboard to prevent the bedbugs from escaping, others drill holes in the walls to apply chemical to kill the bedbugs inside, or apply insecticide dust for long term control. While these methods are all good, I believe that the most effective and long-term solution is to caulk all the entrances to the wall voids in all directions.

4. Your neighbors also had bedbugs, which invaded your home after treatment and caused re-infestation.

The solution to this is the same as above.

5. The bedbugs were resistant to the insecticide used.

Although quite a few recent researches have found significant pyrethroid resistance in bedbugs, the pest control industry still claims that they are in control, which is something that I am not able to explain. Nevertheless, if you see bedbugs in recently treated areas and don't seem to be affected, then it is possible that they are resistant to the pesticide applied. To eliminate these resistant bedbugs, your PCO will have to either increase the dosage (within the certified limit) or switch to another pesticide with different mode of action, although even these measures may not always work. Again, the best way to handle resistance is to adopt an integrated approach and use as many weapons as possible.

There's no doubt that repeated treatment is necessary at this point. However, if it is costing hundreds or even thousands of dollars to remove an infestation now, as more of our neighbors have bedbugs and as pesticide resistance becomes widespread, the required number of treatments will only go up, and this bedbug epidemic will potentially make many people bankrupt. The EPA constantly faces pressure and even lawsuits from various interest groups to cancel or continue the registration of many pesticides, and its decision is often not purely based on scientific facts. As this epidemic starts to cause people serious financial crisis, and as public opinion starts to weigh in, the EPA may be under pressure to reverse some of its earlier actions, or the government may be forced to amend the related legislations. But we don't know if and when this will happen. What we do know is that the pesticides we have are not effective, nor are the treatments, yet we don't have other choices. Besides taking an integrated approach, the best thing we can do at this point is to alleviate the stress and financial losses by improving the effectiveness of treatment, which in turn, can be achieved by eliminating or at least reducing the possible causes of failure, as I suggested above.

Caulk, caulk, caulk!

2007-02-14T11:15:00.000-05:00

So far it seems that I have been opposing the use of insecticides. But that simply isn't true. If we were dealing with cockroaches, then I would say, let's try not to use chemicals. But bedbugs are different, we must use any weapons available to get rid of them. To make strategies such as Rotation work effectively, we will need more insecticides than we currently have. Therefore, in my opinion, if the situation really gets out of control, the government may have no choice but to loose the restrictions on some insecticides. On the other hand, I do believe that it is very dangerous to be over-dependent on chemicals, mainly because of insecticide resistance. Many people believe that if we had DDT, we would have eradicated these bedbugs as we did in the old days. I highly doubt it due to the cross-resistance (knockdown resistance) between DDT and pyrethroids, especially if these bedbugs have originated from a region/regions where DDT or pyrethroids were heavily used. To defeat bedbugs with chemicals alone, we will have to unleash more powerful insecticides than just DDT.

As Deb, a member of Yahoo Bedbugger Group, pointed out after my last post, since bedbugs are mostly in the bed, they don't even need to cross the insecticides on the floor to reach us, and even if we did have access to some powerful insecticides, we wouldn't be able to use them freely in our beds. This is just another reason why we cannot depend completely on chemicals. By combining all weapons available to us, we will effectively improve our chance of winning. For example, if we have two pesticides with different modes of action and with no cross-resistance, each of which gives 70% of control, and two alternative measures, each of which gives 40% of control. By combining the two pesticides, we can theoretically achieve 1-(1-70%)², or 91% of control. Similarly, by combining one of these pesticides with the two alternative control measures, we would achieve 1-(1-70%)x(1-50%)², or 92% of control. And if we combine them all, then we would achieve 1-(1-70%)²x(1-50%)², or 98% of control. In addition, resistance will become less of a problem since the bedbugs that are resistant to one control measure can often be eliminated by another.

Although they can provide temporary control, chemicals alone will not provide long term solutions. Because even if we have successfully removed an infestation today, when opportunity comes, bedbugs will invade our homes again, and we will have to repeat the same painful process of treating multiple times without any certainty of success and storing all our belongings in a storage unit for 18 months. To find a real solution, we need to get to the root of the problem. Yes, it's easy to bring home some bedbugs (or any other pests) accidentally, but they will establish an infestation only if we have a hospitable environment for them. If they cannot find what they need in our homes, they will either leave or die. Therefore, we should first identify the basic elements that bedbugs need to survive, and then remove them.

All insects need three things to survive: water, food, and shelter.

Most insects need water and moisture.

Mosquitoes need water to reproduce. There are two types of mosquitoes. Standing water mosquitoes lay their eggs on standing water, and the larval and pupal stages of all species require standing water to develop. Flood water mosquitoes actually lay eggs in moist soil. Since adult mosquitoes are mobile, hence eliminating breeding sites is always a preferable and more effective way to control mosquitoes. The eradication of malaria in North America is a perfect example of success through the use of an integrated approach. Breeding sites such as swamps, pools and wetlands were either drained or filled, oil was applied to water surfaces to suffocate the mosquito larvae, screening was used on windows and doors to keep mosquitoes out, and the National Malaria Eradication Program helped the final eradication of the disease through the use of DDT.

Since then, unfortunately, the global malaria eradication campaign from 1955 to 1969 has failed, and the Roll Back Malaria movement that started in 1998 is also failing. Today, malaria is re-emerging as the number one infectious disease. There failures have been caused by a number of factors, the most important of which is that not only has the vector (mosquito) developed resistance to pesticides, the malaria parasite has also developed resistance to the drugs used such as chloroquine. We were so confident that science could solve all our problems, so instead of working with nature, we have been forcing our way through with chemicals and biotechnology. But chemicals have limitations, so has biotechnology. HIV viral strains are now showing resistance to drugs that were once effective. A recent research also found that Gentrol, a popular insect growth regulator, caused no reduction in egg production and hatch.

Many insects are also attracted to areas where moisture accumulates. Subterranean termites need constant moisture to survive. Adequate ventilation can effectively reduce the opportunity for termites to build their colony. Cockroaches, silverfishes, sowbugs, pillbugs, springtails and booklices are also heavily dependent on moisture. Certain insects such as springtails and booklices can be eliminated by reducing humidity alone.

I haven't been able to find reliable information on how dependent bedbugs are on moisture. But at least one pest control company, Pestec in California, has conducted experiments on treatment using both heat and dehumidifiers. Insects thrive under some ideal conditions, and the ideal conditions for most insects are between 20 and 30^oC (68-86^oF) for temperature, and between 60% and 80% for humidity.

Insects of course also need food to survive.

Bedbug's food is, unfortunately, our blood. According to BBC Science & Nature, Bedbugs are believed to have originated from the Middle East where they fed on bats living in caves. "Man moved into the caves and when they moved out, the bugs, which had adapted to feed on them, went with them". What a mistake we have made! But as I have suggested many times in the past, bedbug's dependence on our blood is also their weakness. Since I have emphasized enough on "why and how to protect ourselves", I am going to skip it this time. You can read my previous posts for both theories and some practical advices.

Finally, insects also need a safe place to live.

As we all know by now, bedbugs live in cracks and crevices. They also try to be as close to us as possible. So the first choice is the bed, and the next is the chair or the couch. It is possible for them to travel some distance to feed, but this is not preferable, since it will make them not only easier to be detected, but also consume energy. Also, by staying close to us, nymphs will be able to feed immediately after hatching.

I mentioned caulking quite a few times in my previous posts. To understand the importance of it, let's first take a look at the extermination process. The preparation work required by a pest control company often involves moving the furniture away from the wall and removing all bedding and all contents from the closets and the drawers. The purpose of this is to enable the PCO to access all possible hiding places and treat them with insecticides. Insecticides can be classified based on active ingredient, mode of action, method of application, and so on. The WHO even has a classification system based on hazard. PCOs often classify insecticides by method of application, and hence we have Crack and Crevice application, Indoor Surface application, and Indoor Space application. If you are lucky to have a properly trained PCO, then he would use Crack and Crevice application, such as insecticide dusts, for areas that are difficult to reach, such as deep cracks and crevices (some PCOs may even drill holes in the walls to apply insecticide dusts for long term control), Indoor Surface application (usually residual sprays) for areas where bedbugs are most likely to crawl in, and Indoor Space application (aerosols) when harborages are found. Most qualifies PCOs should know how to apply the pesticides. The most challenging work, however, is not how to kill the bedbugs, but where to find them, and I believe that knowing where and how to find all the potential harborage sites is one of the most important characteristics that distinguishes a good and experienced PCO from the rest.

Simply put, a PCO's job is to identify all the potential harborage sites and then treat them with insecticides. What puzzles me then, is how efficient it is to keep vacuuming and treating the same cracks and crevices over and over again. Since the harborage sites have already been located, why not take one step further and remove them by sealing them all? Currently used residual insecticides can last a few months at most before they break down, but caulking can last decades. Even if we are lucky enough to remove the infestation this time, as long as these cracks and crevices exist, our homes will always be vulnerable to future re-infestations. Instead of keeping vacuuming and treating the same cracks and crevices, why don't we caulk them all? By doing so, we will eliminate not only all the bedbugs inside, but also these potential harborage places. Assuming that you are able to locate all the cracks and crevices in your home, then theoretically you can eliminate the whole infestation by caulking alone, and you will also end up with a bedbug proof home. For extra safety, you can always apply insecticides before caulking. Yes, you may still accidentally bring home a few bedbugs in the future, but they will not be able to spread to your neighbors, escape the insecticide treatment, or hide somewhere close to you to wait for a chance to attack you. They will have no place to hide and it will be a lot easier to locate and remove them.

It is true that caulking a whole residence takes a lot of time and efforts. But is it any easier to vacuum and treat all the cracks and crevices over and over again, in addition to all the preparation work for each treatment? A real solution is never an easy one. Many people must have thought that it was ridiculous and mission impossible to install screens in every household and to eliminate every single pool, swamp and wetland. But we have done that, and we are lucky that we have done that. On the other hand, it's not as hard as it seems to eliminate all the potential harborage places. Many things that I have done in the last few months can be done systematically and with much less time and efforts. Firstly, there is money to be made. Sooner or later we will see bedbug proof furniture that have all the joints sealed and have polished metal legs. It took me about half an hour to thoroughly caulk my chair. But manufacturers only need to apply a thin coat of finish to seal all the joints, which shouldn't cost more than a few dollars. Secondly, new legislation and regulations need to be introduced. If your bathroom or kitchen has recently been renovated by a professional, then it probably has also been caulked. This is for energy saving as well as for pest control and is becoming a standard practice. If caulking can be done to the bathroom and the kitchen, then why can't it be done to the bedroom and the living room? It should be made mandatory to have the baseboard caulked before a house can be placed in the market, to have the gap between the light and the ceiling caulked after a ceiling light is installed, and to have bug-proof cover installed on all electric outlets (child safety electric outlet covers are available but I am not sure if they are tight enough to keep bedbugs out). There are many improvements that can be made to our homes and will only add a tiny fraction to the price of a house. There may also be better technologies and easier ways than caulking to eliminate the potential harborage sites for bedbugs. It's not technology or resource that we are lacking. The Centers for Disease Control and Prevention (CDC) was originally founded to combat malaria, we need the same kind of commitment and determination from ourselves as well as from our government to win this war against bedbugs.

As you can see, it is not difficult to figure out the importance of caulking. But while everyone is talking about all kinds of insecticides, very little attention has been given to simple, cheap, but effective measures such as caulking and the use of boiling water. Is it because we are so used to complicated chemical compounds and high-tech devices that we no longer pay attention to all the simple things, and since the sophisticated chemical formulas failed us, we automatically assume that simple measures such as caulking will not make any difference? Or do we just feel that it's safer to follow what everyone else is saying, and to not suggest any new ideas, to avoid the risk of being laughed at by others? Whatever the real reason is, if after spending hundreds or even thousands of dollars we still cannot eliminate one single infestation, then I just don't think that we are doing it right. I am not suggesting that caulking alone can completely solve our problem. As always, I prefer a well-planned strategy that consists of a variety of control measures. But caulking, or eliminating the potential harborage sites for bedbugs to be precise, should definitely be a major component of that strategy.

Managing insecticide resistance

2007-01-31T15:19:00.000-05:00

As I said from the very beginning, the sole purpose of this Blog is to share some of my knowledge and experience with others. Many people chose to move on and leave the horrific experience behind once they removed their infestations, which is understandable. I decided to write something down since I believed that it could be invaluable to others. And because I am a sufferer myself and there is no personal interest involved, it is much easier for me to keep my views unbiased.

Also I would like to make it clear that many of the theories, particularly the recent ones on insecticide resistance, are not based on my personal assumptions, but rather are well established theories with solid technical foundation. I only explained it in my own words to make them easier to understand. Although I am not a pest control expert or entomologist, my background in applied science and first hand experience do help me understand these theories. To make sure not to mislead the readers, I won't make any conclusions without doing adequate research or experiments.

Besides the strategies covered last time, there are a few more practical ones to prevent or delay insecticide resistance.

1. Saturation.

This is to overwhelm the insect population's resistance with heavy dose of an insecticide. As I mentioned before, resistance is a comparative term. By increasing the dosage, even resistant individuals could be killed. The aim is to eliminate the RS individuals since the RR individuals may not be killed even at very high dosage (see my previous post for the labeling of RR, RS and SS). After the insecticide is applied, susceptible individuals may be introduced to mate with the survivors to reduce the frequency of the R alleles. It is generally not practical to use this strategy in a residence since it could cause significant damage to the health of the residents and the environment. (Revised on Feb 23, 2007) But extra dosage can be applied to limited areas, especially where harborages have been found. And intentionally or not, some PCOs do use this strategy. The concept can be borrowed when using non-toxic insecticides such as DE by increasing the dosage, or when using alternative control measures such as cold and heat treatment by extending the time period or by increasing the temperature settings. When applying these control measures, it is important to make sure that all bedbugs are killed, since the survivors are always the most adaptive ones.

The strategy works the best when the targeted area can be isolated and the insecticide leaves no residue. For example, Vikane gas fumigation is being used to treat bedbug infestation and is becoming more and more popular. Since a structure is completely sealed (tented) before fumigation, and Dow AgroScience claims that Vikane leaves no residue, it is possible to increase the dosage rate without causing significant side effects. Currently three times the dosage rate of Vikane used for drywood termites is prescribed for bedbug fumigation. With enough concentration and sufficient penetration time, even eggs can be killed. Vikane chamber can also be used to treat furniture and possibly vehicles. The technique sounds promising and does not cause significant damage to human health or environment. However, the cost of Vikane gas fumigation is significantly higher, and it is impossible to treat a multi-family dwelling without the co-operation of every unit. The long-term effects of using Vikane gas are also not clear.

2. Rotation & Tank mixing

Rotation is a strategy commonly used by some PCOs. Basically, you rotate insecticides with different mode of action. If 0.01% individuals of a bedbug population are resistant to each one of two insecticides, then only 0.000001%, or one in every one hundred millions are resistant to both. So in the example from my previous post, if we applied two insecticides in rotation, then the 100 bedbugs survived the first insecticide would have been eliminated by the second insecticide. Also, resistance is usually not very stable at the early stage of its development, and might revert to susceptibility once the insecticide isn't used. Therefore Rotation may delay the development of resistance.

Tank mixing works in the similar way. But instead of applying different insecticides in rotation, you use them at the same time. For instance, pyrethroid and carbamate "two-in-one" treated bed nets have been used in Africa for malaria vector control to improve the effectiveness of the bed nets. (Updated on Mar 2, 2007. Strictly speaking, treating bed nets with both pyrethroid and carbamate may not be considered as tank-mixing, since pyrethroid and carbamate are applied to different parts of bed nets. Tank-mixing, as the name implies, typically mixes two or more pesticides, and could have some undesirable problems such as incompatibility between pesticides, or reduced overall effectiveness if one pesticide is repellent to the target pest.)

This strategy works only when the insects haven't developed resistance to either insecticide. If resistance to one insecticide is already evident, then basically we would be using only one insecticide, and the insects will eventually be resistant to both insecticides.

Currently, the biggest problem with this approach is that we, including the PCOs, have very limited choices. Many insecticides, especially those broad-spectrum contact and stomach poisons have been banned or restricted in the past due to health and environmental concerns as well as political reasons. Development of new insecticides is also slow and costly due to both technical and bureaucratic reasons. The development of many insecticides in the past has either failed or been rejected due to cross-resistance. The cost of having a product registered is now estimated to be around $100 million, according to Dr. Dini Miller. To make things worse, according to the Federal Insecticide, Fungicide, and Rodenticide Act, all pesticides registered before Nov 1, 1984 are required to be re-examined. Manufactures not only have to pay a re-registration fee, but also need to prove that the pesticide would not endanger human health and environment. Many manufactures simply chose to stop making the pesticide to avoid the heavy cost involved.

3. Integrated Pest Management

The basic rule is to use alternative control measures wherever possible, and use chemical as a last resort. This is not to say that we should abandon chemicals altogether, but rather should use them wisely and more effectively. IPM was practiced well before the arrival of synthetic chemicals, even though the term was formalized in 1969 by US National Academy of Sciences. But since organosynthetic insecticides were so effective when first introduced, all other control measures were virtually abandoned. However, within a decade of its introduction, organosynthetic insecticides started to lead to disastrous consequences such as widespread insecticide resistance, secondary pest development, elimination of natural enemies, environmental hazards, and so on. Since then, the focus has been gradually shifted back towards Integrated Pest Management. Many "soft insecticides" were developed in the 70's and the 80's to target specific pests and to reduce environmental hazard, lots of efforts have also been put into biological control since the 90's. Insecticides are now applied only to the infested area and only when necessary. Today, pest control is no longer as simple as hiring a PCO to spray some chemical. For instance, education and participation of the customer (ourselves) are playing a more and more important role. We all know that preparation is the key to the success of a bedbug treatment. In fact, many PCOs won't even accept the job if the preparation work isn't properly done.

However, since chemical always seems to be a quick solution, when it comes to pest control, most people will only think of chemical. According to a survey (available in Nov 2006 issue of Pest Control Technology) done by our Yahoo Bedbugger Member, Ms. Jody Gangloff-Kaufmann and her colleagues, most PCOs didn't recommend the use of alternative control measures other than throwing away things and vacuuming. This is worrisome since I believe that relying heavily on chemical is one of the main reasons why so many treatments have failed. But PCOs are not the only ones to blame, it's really our own responsibility to do thorough pre- and post- treatment work to help ensure the success of treatment.

Finally I want to cover one more strategy that I've mentioned before, which is to use ourselves as the bait to lure the bedbugs to cross the insecticide and get killed. This is not an official strategy but seems to be gaining popularity. However, as Richard Cooper of Cooper Pest Solutions pointed out in his article "Bed Bugs - Still more questions than answers: a need for research and public awareness" (available in summer 2006 issue of American Entomologist), after an insecticide is applied, bedbugs would typically leave the treated area for four to five weeks, and then come back only if the same insecticide isn't applied again. Insects have much better senses than human beings do, if we don't like chemicals, can we really be so sure that bedbugs will not try to avoid them? In addition, if the bedbug population happens to be resistant to the insecticide applied, this strategy could backfire, especially if you are advised to not protect your bed. I am not opposing the use of this strategy, and I do respect the logical thinking behind this practice, but extreme caution should be taken. As always, it is dangerous to rely heavily on one single control measure, let alone one single strategy. (Revised on Mar 05, 2007. A recent research from Virginia Tech found that none of the insecticides tested including the pyrethroids was repellent to some laboratory strain bedbugs. But since many earlier researches and field observations indicated otherwise, I think it is too early to make the conclusion that pyrethroids aren't repellent to bedbugs.)

Although our choice is very limited, we still have a few insecticides to use. By properly using these insecticides and by combining insecticide treatment with alternative control measures, I believe we still have very good chance to keep bedbugs out of our homes. The strategies covered above can be practically employed in our battle against bedbugs. For example, if the bedbugs are resistant to pyrethroids, then we can try Phantom (Chlorfenapyr), Sterifab (alcohol based), refined petroleum oils, rubbing alcohol ,insecticidal soaps, and so on. By the way, quite a few people from Yahoo Bedbugger Group had success with Murphy's oil soap. Diatomaceous Earth can be dusted along the baseboard so that the bedbugs can't reach you without being detected. If the bedbugs try to live longer by hiding in the cracks and maintaining slow metabolic rate, then we can drive them out with a repellent. Even if they don't get killed by the chemical, don't get detected and killed by us and don't hit the DE on the floor, they will at least consume lots of energy. All we have to do then is to protect ourselves so that they won't get the badly needed food. Can they still live more than one year now? I don't think so. Without sufficient nutrition, they will only be more susceptible to insecticides. If the bedbugs become resistant to insect growth regulator, then we should stop feeding them by protecting ourselves. Remember they need our blood to reproduce? If the bedbugs feel they can escape insecticides by hiding deeply in the cracks, then we can simply caulk the entrance and keep them in there permanently. And if the bedbugs are in the vacuum bag, then we can rinse it with boiling water before throwing it out, the temperature of boiling water is 100 degrees Celsius, twice as much as the temperature required to kill all stages of bedbugs (thermal death point), and is lethal enough to kill instantly on contact!

As you can see, we do have quite a few weapons, why don't we use them all? If a bedbug is resistant to one insecticide, then it will be killed by another insecticide or other measures. By combining all weapons available, we will greatly improve our winning chance. Once we stop focusing exclusively on chemicals and start thinking outside the box, we will see things differently, and there will be options and solutions. By taking an integrated approach, we will have much better chance of defeating our enemy.

Development of insecticide resistance

2007-01-19T08:42:00.000-05:00

Last time we briefly covered some basic theories about insecticide resistance, which is that as long as genetic variation and the selection pressure - insecticide applications are present, insecticide resistance is inevitable. It's a matter of time before resistance will develop, and the process cannot be controlled, although can be delayed by the proper use of the insecticide. Today we are going to look at the development of insecticide resistance in some depth.

Let's start with some simple calculations. Suppose that there are one million bedbugs in a local area, and we are going to treat the area with an insecticide. The number one million is chosen so that we can get some meaningful number of resistant individuals to start with.

First, the following assumptions are made:

initial population is 1 million

the insecticide provides 90% control of the susceptible individuals

0.01% or 100 (1 million x 0.01%) initial resistant individuals

After the first insecticide application

100 resistant individuals survive

10% of susceptible individuals survive, 10%x(1,000,000-100)=99990

population after first treatment=99990+100=100090

percentage of resistant individuals after first treatment=100/100090 = 0.10%

By repeating the same calculation for each insecticide application, table 8.1 was created. Then by changing the percentage of control to 80%, table 8.2 was created.

# of treatments	starting population	# of resistant bedbugs	# of survived susceptible bedbugs	final population	% of resistant bedbugs
1	1000000	100	99990	100090	0.10%
2	100090	100	9999	10099	0.99%
3	10099	100	1000	1100	9.09%
4	1100	100	100	200	50.00%
5	200	100	10	110	90.91%
6	110	100	1	101	99.01%

Table 8.1 - insecticide provides 90% control of susceptible individuals

# of treatments	starting population	# of resistant bedbugs	# of survived susceptible bedbugs	final population	% of resistant bedbugs
1	1000000	100	199980	200080	0.05%
2	200080	100	39996	40096	0.25%
3	40096	100	7999	8099	1.23%
4	8099	100	1600	1700	5.88%
5	1700	100	320	420	23.81%
6	420	100	64	164	60.98%

Table 8.2 - insecticide provides 80% control of susceptible individuals

A few conclusions can be made from these two tables:

After each round of treatment, the number of susceptible bedbugs decreases, while the percentage of resistant bedbugs in the population goes up. Therefore, the more frequently the same insecticide is applied, the quicker resistance will develop. Similarly, the longer residue an insecticide has, the longer the bedbugs are exposed to the insecticide, and the quicker resistance will develop.

By comparing the two tables, we can also conclude that the more susceptible bedbugs get killed, the higher the selection pressure becomes, and the quicker resistance will develop.

Resistance will start to spread only after reproduction starts. Without reproduction, all the susceptible bedbugs get eliminated, only 100 resistant bedbugs survive, and the population is reduced from 1 million to 100, which is actually a great achievement. But once reproduction starts, the population can get back to 1 million within a few months, based on the calculations I demonstrated in my previous post "How fast can bedbugs multiply - Part 1". And that would be a population that cannot be controlled by the same insecticide anymore.

The rate at which resistance develops also depends on how fast the insects reproduce. A faster reproduction rate means that more generations of the insects will be exposed to the insecticide, and therefore will speed up the selection process.

Consequently, an important conclusion can be reached at this point, which is that insecticides should be applied as infrequently as possible. Firstly, this will slow down the selection process, and hence will slow down the development of resistance. Secondly, this will keep some susceptible individuals alive, so that the susceptible trait will be passed onto the offspring. This strategy is commonly practiced in agriculture. A grower would first establish an economic threshold, and insecticides will not be applied as long as the economic loss remains below the threshold. The concept is also a major component of Integrated Pest Management.

Once reproduction starts, another important factor, the frequency of the resistance alleles will be involved. Let's take a look at some background theories first.

An allele is any of a number of alternative forms of a gene. Most insects have two copies of each allele. For illustration purpose, we label resistant allele with R, and susceptible allele with S. So the combinations, which are termed genotypes, are RR, RS, or SS.

Resistance can be dominant, semi-dominant, or recessive. If dominant, then only one copy of resistant allele is required to have full protection against the insecticide, since the R allele masks the S allele. In this case, the genotypes are either RR or RS, but RR has higher degree of resistance than RS has. If recessive, then two copies of the same allele are required to have full protection, and the genotype is SS. Finally if resistance is semi-dominant, the alleles are still RS, but the dominance is incomplete and only provides partial protection, i.e., protection against lower amount of toxin.

During reproduction, each parent contributes one of the two alleles to their offspring. The combinations as well as the chance of passing the resistance trait to the offspring are shown in table 8.3. By comparing the percentages in the two columns, we can see that when resistance is dominant, the chance of passing the trait to the offspring is much greater than when resistance is recessive.

Allele frequency is a measure of how common an allele is in a population. Similarly genotype frequency is a measure of how common a particular genotype is in a population. Assuming that the ratio of the genotypes RR:RS:SS is 1:2:1 (by the way, the phenotype ratio is 3:1 for dominant resistance, and 1:3 for recessive resistance), then the frequency of the R alleles is (2x1+1x2)/8, or 0.5, and the frequencies of the genotypes RR, RS, and SS are 0.25, 0.5, and 0.25, respectively, simply because the ratio is 1:2:1.

The Genotype frequency is generally determined by the allele frequency (subject to some conditions). For instance, if the frequency of the R alleles is 0.5, then the chance of getting a R allele from each parent is 0.5, hence the chance for the offspring to get a RR is 0.5 x 0.5, or 0.25. This is similar to the calculation of probability of getting heads in coin tossing. The chance of getting heads once is 0.5, and of getting twice is 0.5 x 0.5, or 0.25, and so on. By the same token, if the percentage of the individuals in a population that are resistant to each one of two insecticides is 1%, then the percentage of the individuals that are resistant to both insecticides is 1% x 1%, or 0.01%. The genotype frequency can also be calculated using the Hardy-Weinberg model. If the frequencies of the allele R and S are p and q, respectively, then the frequencies of RR, RS, and SS are p², 2pq, and q², respectively.

parents	offspring genotypes	% of resistant offspring
parents	offspring genotypes	dominant	recessive
RR x RR	RR, RR, RR, RR	100%	100%
RR x RS	RR, RR, RS, RS	100%	50%
RR x SS	RS, RS, RS, RS	100%	0%
RS x RS	RR, RS, RS, SS	75%	25%
SS x RS	RS, RS, SS, SS	50%	0%
SS x SS	SS, SS, SS, SS	0%	0%

Table 8.3

Basically, since resistance is usually recessive, hence only the RR individuals are resistant to the insecticide. And because the frequency of the genotype RR is determined by the frequency of the R alleles, therefore, the key is to keep the frequency of the R alleles under control. There are a few ways to do this. The first is to minimize the use of insecticides so that we can keep some S alleles in the population, as mentioned above. The second is to intentionally keep a few areas unsprayed to provide refuge to the susceptible individuals. This is called the refuge strategy. The third is to raise susceptible individuals in the lab and then release them to the field periodically. For instance, if we have 100 RR individuals, 200 RS, and 100 SS, then the frequency of the R alleles is (100x2+200x1)/(200+400+200), or 0.5. By introducing another 200 SS individuals into the population, the frequency is lowered to (100x2+200x1)/(200+400+200+400), or 0.33. We can also look at this from a different angle. When a RR individual in the field mates with a SS individual released from a lab, the offspring is RS, and is susceptible to the insecticide. The last two strategies will work only if the resistance is recessive and if resistant individuals and the susceptible ones are nearby so that there is a good chance for them to mate with each other. The strategy does not work well with dominant resistance, since the offspring (RS) will still be resistant, although the degree of resistance is lower than that of RR individuals.

Since a bedbug population is normally confined to one residence, and no new susceptible individuals are introduced into the population, therefore with each round of treatment, the insecticide kills only the susceptible individuals, and effectively increases the frequency of the R alleles and causes resistance to spread (within the population). In addition, bedbugs can have 3 to 4 generations a year, and at the time of writing the average number of treatments required to eliminate them from one household is 3, meaning that multiple generations are often exposed to the same insecticide. The combination of these factors can result in rapid spread and high degree of resistance (several thousand-fold resistance to pyrethroids in some cases, again according to the University of Kentucky report). By the way, I suspect that the average number of treatments required could be higher than 3 and resistance might have already played a role. For instance, if a person had a PCO treat his residence twice, later he found out that the treatments failed and had another PCO treat his place three times. The first PCO wouldn't record this as a failure since the person did not call back, and the second PCO would record it as a success after 3 treatments, instead of 5.

To make things worse, although the strategies mentioned above are very important and have been proved effective in agriculture, it might be difficult to practically use them to fight bedbugs. The reason is simple, we have no tolerance for bedbugs and the only acceptable number is zero, and it's quite unlikely that anyone is willing to keep or accept some susceptible bedbugs in his/her home (just imagine that a PCO comes to your home and releases a few hundred non-resistant bedbugs...). This makes our task even more challenging. However, the good news is that, as I repeated many times in the past, while it's almost impossible to control the reproduction of agricultural pests, it is possible to stop bedbugs' reproduction process by protecting ourselves (for how to protect yourself, see my previous post "How to isolate your bed"). Resistance will start to spread only after reproduction starts.

Next time we'll look at some more practical strategies.

Myths about insecticide resistance

2007-01-11T13:42:00.000-05:00

I wasn't going to touch the topic of insecticide resistance, because I don't have much background in this field. But since insecticide treatment remains one of the most important control measures, and many people choose to do treatments by themselves, I decided to cover it. Since insecticide resistance is the biggest issue that we are facing right now (at least in my opinion), I am going to focus on it for a while. However, the goal is not just to collect information, but to understand it and use it to our advantage. Knowledge is the best weapon we can have against this evil creature.

Although I've done extensive research and tried to digest the material before writing, mistakes could be present, so please don't hesitate to correct me.

Enough has been said on why and how to protect your bed. The principle is the same for how to protect yourself during the day, so I won't go through all the details. After I moved to my new place, I bought a table with four round metal legs and without retractable keyboard, and caulked my chair as soon as I bought it. Since my infestation had started, I have been resting my feet on a stool while I am at my computer, with both the chair and the stool protected by Vaseline. For upholstered furniture, my only suggestion is to not use them until the bedbugs are gone. You may or may not need to do all these, depending on the severity of your infestation. I just don't want to take any chance. If you are able to successfully protect yourself for a few months, you may start to relax a bit, since nymphs can only survive for a few months without feeding, and adults are easier to detect. Hopefully you will also stop wondering if the little dots on your body are nymph bites or phantom bites as I did.

Now you have set up your defense, it's time to launch your assault, and you will need some weapons. Naturally you will think of insecticides. As we all know, insecticides can cause side effects to our health and environment, but like many others, I can honestly say that if I could choose between the suffering from these side effects and the suffering from bedbugs, I'd choose the former. My real concern is insecticide resistance.

There are some myths about insecticide resistance.

1. Insecticides create resistant insects
Insecticide applications don't create individual resistant insects. Instead, due to genetic variation, there are almost always a few rare individuals in the population that are naturally resistant to the insecticide applied. These individuals usually exist before the insecticide is even applied. Insecticide applications simply remove the susceptible individuals. The resistant individuals survive, mate and pass the resistance trait to their offspring. Eventually the whole population will be resistant to the insecticide. This is basically an ecological selection process, with the insecticide being the selection pressure (more on this next time).

2. Insects only develop resistance to chemical insecticides.
Insects can develop and have developed resistance to virtually all classes of insecticides. Metabolic resistance is the most common. Insects possess this mechanism are able to detoxify the insecticides with their enzyme systems. Resistance to biological insecticides such as growth regulators has also been frequently reported. Resistance to inorganic insecticides was discovered before the development of organic insecticides such as DDT. Diatomaceous Earth belongs to the group of inorganic insecticides. A study has found that Tribolium Castaneum had developed resistance to DE. I don't have access to the full content of the article, but according to the abstract, behavioral resistance was obviously involved. Insects possessing this type of mechanism are able to avoid the insecticides by changing their behavior. Behavioral resistance has been reported for a few classes of insecticides including pyrethroids. However, behavioral resistance is generally less threatening since the insects simply avoid the insecticide instead of detoxifying it, hence the insecticide can still serve the protective purpose. For example, if DE is dusted around the bed, the bedbugs will have to make a decision between crossing it and starving, and either way, they will die. There might have been another mechanism involved though, with which the resistant insects were able to lose water at a slower rate than the susceptible ones. Even though the study was on Tribolium castaneum, the finding is worrisome since DE is one of the main weapons that we are using against bedbugs.

Pyrethroid insecticides were once thought almost perfect since they were broad spectrum, low cost, low odor, quick acting, relatively low toxic, and relatively non-persistent in the environment. It was even believed that since they provided such quick knockdown effects, insects would not be able to develop resistance to them. However, at least three resistance mechanisms have been discovered in many insect species. The first one is target site resistance. Pyrethroids kill insects by holding the sodium channels of the nerve sheath open. But resistant insects are able to reduce their effectiveness (lowered sensitivity) due to mutations in sodium channel genes. The second one is metabolic resistance (detoxification with enzymes), and the third is behavioral mechanism, as mentioned above.

Beside insecticides, insects can also develop resistance to other environmental stresses such as heat, cold, starvation, desiccation, and so on. We already know that some bedbugs can live for 18 months without feeding, and can withstand extreme temperatures. The thermal death point for bedbugs is 45^oC, but don't assume that this will never change in the future. Could "isolating the bed" cause bedbugs to develop further starvation resistance? The answer is yes and no. If you are able to successfully protect yourself, then this won't happen. Because firstly resistance is a comparative term, even resistant individuals can only tolerate stress caused by starvation (or heat, cold, chemical etc) to a certain degree, and will eventually die without food. Secondly, without blood meals, bedbugs will not be able to reproduce, and hence will not be able to pass the resistance trait to the offspring. However, if you aren't able to protect yourself successfully, selection process may start provided all these conditions are met: a few resistant individuals are present, the starvation period is long enough to kill the majority of the susceptible bedbugs while not long enough to kill the resistant ones, the resistant bedbugs are able to feed to reproduce and the offspring are able to find blood meals for growth. The chance for this to happen is slim nowadays, but the process must have repeated numerous times in the past for bedbugs to be able to survive for such long period of time without feeding today. This also shows how dangerous it is to completely rely on one single control measure, regardless of whether it's starvation, chemical or anything else. Resistance to starvation is likely associated with slow metabolic rate.

3. Resistance takes long time to develop, so we don't need to worry about it now.
Resistance can develop very fast if insecticides are not used properly. The insecticide properties of DDT were first recognized in 1939. Resistance was first reported in houseflies in Sweden in 1946, only two years after its introduction there. Due to cross resistance, resistance can develop very fast or even exist before the insecticide is used. Cross resistance occurs when an insect population that has developed resistance to one insecticide exhibits resistance to other insecticides in the same chemical classes (also termed class resistance) or insecticides in the different class but have the same mode of action. For instance, cross resistance between DDT and Permethrin has already been discovered in some mosquito species. Although they are not in the same chemical class, they both target the sodium channels.

4. The more insects we kill, the better control we achieve
In terms of resistance control, this is not true. There are two reasons for this. First, only susceptible insects get killed and the resistant ones survive, therefore, the higher the mortality is, the higher the selection pressure is exerted on the insect population, and the quicker the selection process is carried out. If the insecticide kills all susceptible individuals, then the whole population will be resistant, rendering the insecticide useless. Second, susceptible insects are needed to dilute the resistance alleles (more on this next time).

5. The insects are resistant to the insecticide, so we should abandon it.
There are three reasons why this may not be true.
First, resistance could be localized. This is particularly true with crawling insects such as bedbugs. Although they are good hitchhikers and a few individuals might migrate to the neighbors, the population is generally confined to one residence. If a population in one residence appears to be resistant to an insecticide, it could be due to one of two reasons. First, repeatedly failed treatments caused the population to develop resistance. Second, the few bedbugs that started the infestation (from a hotel or a neighbor) were resistant to the insecticide. In either case, it would not provide good indication that resistance has spread to the whole neighborhood, although it will eventually. So after you read the University of Kentucky report (see my previous post), don't jump to the conclusion that all bedbugs are resistant to pyrethroids. If you read the first paragraph carefully, you will notice that the number of sampled sites was only four for Kentucky and Ohio, or two per state, too small to provide any meaningful indication of how widespread resistance was.

Second, the insecticide might still provide effective control even though the effectiveness has declined. For instance, although mosquitoes have been able to quickly develop resistance to DDT, DDT is still being use in Africa to fight malaria. However, the focus has been shifted from eradication to control. Since DDT irritates mosquitoes, indoor spray can effectively reduce malaria mortality by keeping mosquitoes out. After all, the ultimate goal is to reduce mortality rate rather than to kill the vector.

Third, individuals that possess the resistance gene usually lack other advantages that the susceptible individuals have. This is termed fitness cost. For instance, fitness cost could make resistant individuals more vulnerable to natural enemies. Therefore, in the absence of selection pressure such as an insecticide application, the frequency of resistance may drop, although this is not always guaranteed and the rate may vary. After the ban on DDT in Sri Lanka, DDT resistance has constantly reverted to susceptibility, but at a very slow rate. However, if no fitness cost is associated with resistance, then there is no reason for reversion to occur, hence resistance becomes stable and the insects will never lose the trait.

So now we know that insecticides have limitations. When used indiscriminately, they could cause significant consequences, such as shortened useful lifetime of the insecticides and resistant insect populations. Currently there are seventeen insect species that are resistant to all classes of insecticides, hopefully we won't create some super bedbugs that can never be eliminated by insecticides. On the other hand, if used properly, insecticide application remains an important control measure. The key, however, is to not rely heavily on one single control measure, but to take an integrated approach and combine all weapons available.

How fast can bedbugs multiply? - Part 2

2007-01-05T08:53:00.000-05:00

Last time we reached a conclusion that it would take only a few months to have a heavy infestation, today we'll see how the infestation can be control by limiting the food supply.

First of all, here's some background information:

Male bedbugs need to feed before mating

Female bedbugs need to feed before laying eggs

There are five nymphal stages, and at least one blood meal is required for each nymphal stage for the nymphs to molt successfully

Therefore, a total of seven blood meals are required to create an adult bedbug. You may argue that the male might mate multiple times and the female might lay a few eggs after each meal. This may be true. However, nymphs feed a lot more frequently than once every nymphal stage, and the adults need to feed just to survive. Therefore, 7 meals are actually very conservative estimate. Let's assume all meals follow the "breakfast, lunch, dinner" pattern of three bites, then, to generate a new adult bedbug, they will have to bite you at least 21 times.

Now let's assume that you get bitten three times a day (That's a lot of bites considering that you have effectively protected yourself). You will have 21 bites per week, just enough to generate a new adult bedbug. In three months, you will have 14 bedbugs, including the original 2. Remember without limiting the food supply, the number reached 1000 in three months? That's 14 versus 1000, what a difference? Also, after 10 months, some bedbugs will start to die, since the growth is linear, whenever a new bedbug is created, another one will die, and the population will stop to grow.

If you have successfully isolated your bed and living areas, you shouldn't get any bites at all.

Bedbugs cause problem because they bite us, but this also makes them vulnerable since they rely too much on our blood. By protecting ourselves, we can effectively eliminate their food supply, break their reproductive cycle, and make them more vulnerable to insecticides (due to lack of nutrition).

You might be advised not to isolate your bed for two reasons:

1. If the blood meal isn't available, the bedbugs might spread to other rooms.

2. Some pest control companies want you to use yourself as the bait, and lure the bedbugs to cross the insecticides and get killed.

The first reason does not make too much sense to me. It's too big a price to pay to feed them with your blood and let the population grow just so they won't spread to other rooms. Caulking is an effective way to prevent them from spreading by the way.

As for the second reason, the strategy sounds good and might be working at this point. But there are questions you need to ask yourself and things you need to consider:

1. Are you mentally strong enough to commit to this kind of strategy?

2. Bedbugs may not take the bait. Behavioral resistance is common among insects. Insects developed this mechanism will simply stop feeding to avoid insecticides.

3. Pyrethroid resistance has already been reported and is becoming more widespread, according to a report by the University of Kentucky. The more frequently the same class of pesticides is applied, the quicker resistance will develop, and I believe this is the case with pyrethroid-based insecticides right now. As the bedbug epidemic becomes widespread, resistance will become widespread as well, especially because most people including many PCOs still equate pest control to chemical control.

I have spent lots of efforts on "Why and how to protect yourself" so far. A member of our Yahoo Bedbugger Group suggested me to put more emphasis on the topic, and I also thought it was important, since "eliminating the food supply" is an essential part of Integrated Pest Management, a concept that my whole strategy is based upon.

How fast can bedbugs multiply? - Part 1

2007-01-02T09:49:00.000-05:00

I started caulking my parent's place in late September, and my new apartment in November, now the work is nearing the end. Looking back, I probably should have stayed in the old apartment, just to prove that I can defeat the bedbugs, and to make my strategy more convincing. But the place had cracks everywhere and would have taken too much effort to seal them all, and I had two infestations to take care of at the same time, a damaged ceiling to repair, a scratched car to fix (I was thinking about how to fight the bedbugs while I was driving). I was physically and mentally exhausted and just wanted to get out. However, my parents did stay and the battle there is still going on.

Back to the main topic.

Suppose you accidentally brought home two bedbugs, one male and one female, how fast can they multiply with unlimited blood meals? Without using complicated mathematics, the result can be obtained easily with spreadsheet.

There are different data on bedbug's life cycle on the Internet. I tried to use the average and made the following assumptions:

- sex ratio is 1:1

- 10 months of life span

- eggs hatch in 10 days

- nympal development time is 60 days

- female lay 4 eggs per day

click the image to enlarge

Based on these assumptions, the spreadsheet was then setup and a graph was plotted, which contained three periods:

Period I: from day 1 to day 10, eggs are laid daily, number of bedbugs remains constant at 2.

Period II: from day 11 to day 70, eggs start to hatch, number of bedbugs starts to increase, but growth is linear at the rate of 4 per day, and reaches 242 on day 70.

Period III: From day 71 and on, nymphs start to mature, number of bedbugs increases exponentially, total number quadrupled in 20 days to more than 1000 on day 93, or in 3 months.

Just for your information, the number reaches 5000 on day 114, and 10000 on day 129. Stephen Doggett, an entomologist at the institute of clinical pathology and medical research at Westmead hospital in Sydney, said he once found 5,000 bugs in one woman's bed. So it is realistic to have a few thousand of bedbugs in one residence, provided that there are enough food supply and harborage places.

Here's how I set up the spreadsheet:

Columns:

A: number of days

B: number of total adults

C: number of female adults

D: number of newly hatched 1st instars on this day

E: number of eggs laid on this day

F: total number of nymphs

G: total number of bedbugs

Formulas for each column:

A: From day 1 to day 365

B: It's 2 in period I and II. Starting day 71, the formula becomes B71 = B70 + D11, meaning the number of adults on day 71 is the sum of the number of adults on the previous day and the number of 1st instar hatched 60 days ago (and matures on this day).

C: C1=B1*(1/(1+1)), where B1 is the number of total adults, and 1/(1+1) is the female percentage of the population.

D: It's zero in period I. Starting period II, the formula is C11 = D1, meaning the number of newly hatched 1st instar is equal to the number of eggs laid 10 days ago (eggs hatch in 10 days).

E: E1 = C1*4, eggs laid on this day is the number of eggs laid per day by each female multiplied by the total number of female adults.

F: Total number of nymphs is equal to the sum of 1st instar hatched in the last 60 days, the ones born earlier already matured and are added to column B instead. Since we can't use zero or negative numbers as the row number, we enter this formula on cell F60: F60 = SUM(D1:D60), and then copy it downwards. For row 1 to 59, we alter the formula to F60=SUM(D$1:D60) and copy it upwards. The dollar sign makes the summation always start from row 1, otherwise you will get error.

G: G1 = B1 + F1, total number of bedbugs is the sum of total adults and total nymphs.

After 10 months, another event will kick in, which is that the bedbugs will start to die. However, the number is negligible compared with the huge base, so this wasn't taken into consideration.

Also, 100% survival rate was assumed for all stages of life cycle, hence the result might differ a little in reality.

(Revised on Feb 25, 2007) From what I have researched so far, female adults lay 200 to 500 eggs over a period of two months. Therefore, in my calculations, the number of eggs laid should be reduced accordingly after day 130. But this will not affect the results that we have obtained above, because we were only looking at a period of about three months.

The conclusion is that it only takes a few months to have a heavy infestation, you need to catch it early and take care of it as soon as possible, once the number increases exponentially, it will be out of control. Next time we'll examine how the numbers change if the food supply is limited.

Defeating the airborne bedbugs

2006-12-27T13:01:00.000-05:00

Another update on my situation:

Although I took all the precaution while I was moving, I isolated my bed and started caulking as soon as I moved to my new apartment.

Since my problem started, I had a total of about three dozens of bumps that were big, itchy and lasted for weeks. I haven't had any of those ever since I isolated my bed and the working area. But instead I was getting 2 or 3 bumps or dots per week that were small, weren't itchy and disappeared quickly. This lasted until the end of November, a month after I moved. However, since the beginning of December, I haven't had any anything suspicious on my body. I haven't been able to find an explanation for this.

Right after I caulked the ceiling lights and the vents, I caught two spiders on the ceiling. I hadn't seen any spiders before and haven't seen any ever since. So this seems to support my view that caulking is effective against not only bedbugs, but also many other insects such as cockroaches and spiders.

Back to the main topic.

As soon as you isolated your bed, two things might happen:

1. The hungry bedbugs become reckless and come out more often during the day. This happened both at my old apartment and my parents'.

2. The bedbugs alter their normal routes and start to climb onto the ceiling and drop to your bed. My parents caught two on the ceiling right above the bed. I've also read at least a dozen of articles on the Internet that described this strategy used by the bedbugs.

I'll focus on how to defeat the airborne bedbugs today. I doubt that the bedbugs possess human intelligence, as suggested by Dr Campbell in his paper "My observations on bedbugs", but rather believe that the strategy is based on basic instinct, which is that the bedbugs are attracted to CO2 and body heat. One web site claims that the bedbug can detect CO2 from 15 feet away. I haven't been able to verify that.

My suggestion is that if you have a light infestation, you don't have to worry too much about it, but if you have a heavy infestation or if you have seen them on the walls or the ceiling, you definitely have to do something about it. Here are a few things that I would suggest:

1. Dust Diatomaceous Earth along the baseboard, as I suggested before. DE serves two purposes. If you apply heavy amount, the bedbugs will most likely try to avoid it, so DE acts as a barrier in this case. If you apply lightly, the bedbugs might cross it and eventually die.

2. Eliminate hiding places on the ceiling so that they won't nest there. As long as you have something on the ceiling, whether it's a light, fan or vent, there must be some places for the bedbugs to hide. It's important to eliminate these hiding places especially if you live in an apartment or condo, since they will lead to the drywall above and to the residence above eventually.

3. Spray long residual insecticide along the edges of the ceiling as a barrier.

4. If all fail, I developed two systems that should effectively defeat these airborne bedbugs.

Figure 4.1, top view

The first system is simply a rectangle of double-sided carpet tape on top of painter's tape. As shown in Figure 4.1, the rectangle should be at least a few inches bigger than the perimeter of the bed. I actually used this in my old apartment right after I read "My observations on bedbugs". But I mistakenly had carpet tape on top of duct tape, which damaged the ceiling paint when I peeled them off, and I had to repair the ceiling and repaint it. You also don't want to coat Vaseline directly on the ceiling since it will likely be absorbed by the ceiling and leave black marks on it. The painter's tape that I bought from Home Depot was rated for 14 days, meaning that it could be left up for 14 days without leaving residue on the ceiling. The longest one is 60 days, but is less adhesive. If the tape is left up for too long, it could possibly cause some damage, but I think the damage would be very minor. However, I haven't done any experiment, so do it at your own risk. To avoid the messy looking, you might want to tape along the edges of the ceiling instead.

Figure 4.2, tilted bottom view

Figure 4.3, side view

The second system is a plastic sheet, such as painter's drop sheet with double-sided carpet tape adhered to all four edges, and taped or nailed to the ceiling at the four corners. The basic setup is shown in Figure 4.2. The side-view in Figure 4.3 shows that only the four corners are attached to the ceiling. The main advantage of this system is that:

1. The first system works only on completely flat ceiling, while this system works on ceilings that aren't perfectly flat such as texture ceilings.

2. Since only the four corners are attached to the ceiling by tape or nails, it will cause none or very minor damage to the ceiling.

Because the plastic sheet isn't tightly against the ceiling, bedbugs can keep crawling on the ceiling under the sheet, but they won't be able to reach your bed in this case. And if they try to crawl onto the sheet, they will be blocked by the carpet tape. Better yet, bedbugs are not good climbers, if you also have carpet tape on the other side of the sheet, and if any bedbugs drop from the ceiling onto the sheet, they will be trapped.

Of course, with these tape and sheet on the ceiling, your bedroom won't look too neat. But would your pay this small price or rather let them drop to your bed and bite you?

How to isolate your bed

2006-12-18T14:29:00.000-05:00

Once you discover that you have bedbugs, the first thing to do is to isolate your bed. Bedbugs do come out during the day, but most of time they bite you in the night when you are sleeping. There are a few major benefits of isolating your bed:

1. As I mentioned before, this is the most effective way of controlling their population.

2. Bedbugs cause much more damage to our mental health than physical health. Keeping them away from your bed will ensure you better sleep, reduce your anxiety, and give you the energy needed to fight the war against them.

3. Without food and nutrition, they will be more vulnerable to insecticides.

There are some good web sites that offer great tips on how to isolate your bed. Here are a few:

The bedbug war : step-by-step instruction and photos.
The bedbug blog : one of the most popular sites, but isn't updated too often now.
Bedbugger : another popular site, tons of useful and up-to-date information.
Wikipedia: a free encyclopedia, relatively more reliable and scientific information.
Yahoo Bedbugger Group: a support group including many experienced warriors and some entomologists and pest control experts.

I won't go through every detail but will rather provide some brief explanation and then add a few more points based on my own experience. A picture is worth a thousand words, for those of you who don't like to do all the readings, I made a picture that would give you a quick start. All the parts are actually 3D models. Feel free to use, modify or distribute it for non-commercial purpose.

click the image to enlarge

The basic idea of "isolating your bed" is to have as few contact points between the bed and adjacent objects as possible, and then create barriers at the contact points.

To have minimal contact points, you need to:

Pull the bed away from the walls so that your bed, pillow, blanket and sheet won't touch the walls.

Raise the bed with bed riser so that your blanket and sheet won't touch the floor. But I prefer to have a bigger bed instead.

Eliminate the clutter under the bed to ensure that nothing touches the bed.

Next, you need to create some kind of barriers on the bed legs. Here are a few options:

Place the bed legs in plastic or metal containers, than wrap carpet tape or sticky fly tape around the container. The advantage of doing this is that it won't cause any damage and mess to the bed legs.

Wrap carpet tape directly around the bed legs. I personally wouldn't recommend this, since once you have dust on the tape or accidentally kick the tape a few times, they won't be as sticky any more and need to be replaced. But it's very difficult to peel them off and will likely cause damage to the paint if you have metal frame. Carpet tape is the strongest that I could find. I wouldn't use masking tape or duct tape.

An alternative to the above is to use single sided carpet tape, with the sticky side out, then have scotch tape on both ends so that the bedbugs won't crawl under the carpet tape.

Coat the bed legs with Vaseline. This method was used in the old days and is my favorite since it won't cause any damage and is easy to clean up.

Then, you need to isolate the mattress, the box spring, the pillow, and the blanket:

Wash and dry the pillow and blanket on hot setting.

Use zippered cover for everything and tape the zipper, use light colored covers so that it's easier to spot the bedbugs, and leave the mattress cover on for at least one and a half years.

Vinyl mattress covers are difficult to grip and are not ideal place for the bed bugs to lay eggs, but are easy to tear/rip. I prefer fabric ones. Some people use both.

Treat the mattress and the box spring with chemical if necessary. The first instars are only 1mm long so it's easy to miss one or two.

One last thing that people don't pay much attention to and is rarely mentioned on any web site is caulking. Even if you have metal bed frame, there are still hiding places. You need to caulk all the joints of the bed frame and the slats if you have them, again remember the first instars are only 1mm long. Lie on your back on the floor or turn the bed frame upside down, bed bugs tend to go under than over. Use latex caulking instead of silicone if you need to disassemble the bed in the future, since silicone is difficult to remove. I'll write more on caulking in the future.

Also, if you are planning to replace your bed, get a metal frame. It's more difficult to climb and has less hiding places than wood frame. To quarantine a protected bed, make sure that no kids and pets are allowed in the bed during the day, and store clean clothes in the bed during the day and take a shower before entering the bed.

If after all these steps you still get bitten. It could be due to one of these reasons:

1. Barriers will prevent bedbugs from getting into your bed, but will not kill the ones that are already in your bed. You might have missed a few joints or didn't caulk correctly, or caulking might have shrunk, so double check and apply chemical if necessary.

2. Your pillow, blanket, or sheet touched the wall or the floor.

3. There was a tear in the mattress cover, the cover wasn't taped correctly or the tape peeled off.

4. The bedbugs crawled onto the ceiling and dropped to your bed.

The first three causes are easy to deal with. The most difficult one is the last one, I will write more on this next time. Thanks to nobugsonme, the author of Bedbugger for reminding me to add #3 cause.

Finally, Diatomaceous Earth (DE) can be dusted around the bed for extra safety, and along the baseboard so that any bedbugs that climb the walls will eventually die. Be sure to use food grade DE (amorphous silica) instead of swimming pool DE (crystalline silica) and do wear a mask. According to Wikipedia, crystalline silica poses inhalation hazard because it can cause silicosis. Amorphous silica can cause dusty lungs, but does not carry the same degree of risk as crystalline silica does since it contains very low percentages of crystalline silica.

(revised on Jan 20, 2007) Bedbugs do come out during the day, especially when they are hungry or after an insecticide is applied. The principle is the same for how to protect yourself during the day, so I won't have a separate post for that. They want to be as close to you as possible, so the next choice after the bed would be the chair and the desk (I wouldn't use upholstered furniture until the bedbugs are gone). Caulk the joints to make sure there's no hiding places for them, and then create barriers on the chair/desk legs with vaseline or tape. If the infestation is heavy, I wouldn't even set my feet on the floor while I am at the computer, but would rather put them on a stool, which is also protected by vaseline or tape.

Why extermination fails & My strategy

2006-12-12T15:50:00.000-05:00

Here's a quick update on me:

I isolated my bed immediately after I caught the first nymph, thanks to the method I found on this Blog . I had no more bites for about three or four days, then I caught another nymph in my bed, later on I discovered that there were gaps in the joints on the underside of the bed frame, so I caulked them again. I haven't had any bites since then, although occasionally I did get some mysterious bumps that were tiny, weren't itchy and disappeared quickly. I started caulking my apartment and my parents', in the meantime I was preparing for moving.

I moved out in November. I am not sure if I have brought any bedbugs with me, but I isolated my bed and started to caulk the new apartment immediately. My parents caught two more adult bed bugs on the ceiling, right above their bed in September. Then two months later, they caught one more on the floor. They still haven't been bitten yet.

I don't think we can claim victory yet. In fact, one probably can never be able to do so, especially in a multi-family dwelling, since the bedbugs might just go dormant for a few months or spread to the neighbors and then come back again. But as long as we don't get bitten by them, I can confidently say that we are wining (see below for reasons).

I developed a simple strategy right from the beginning. To understand it, you first need to understand why extermination fails. I believe that there are three reasons why it is so difficult to get rid of these bugs:

1. There aren't many effective pesticides available due to insecticide resistance and the banning of some more powerful insecticides.

2. The bedbugs constantly lay eggs and most chemicale aren't able to kill the eggs, the eggs hatch after extermination and cause new infestation again.

3. The bedbugs hide between walls during extermination and come back out once the chemical breaks down.

(revised on Feb 23, 2007. Initially I believed that no insecticide was able to penetrate the eggshell, and concluded that no insecticide was able to kill the eggs, as many other web sites do. This is apparently inaccurate, since some contact killers do have the potential to kill eggs.)

I developed the following strategy based on the above theory:

We are always advised to let the exterminators handle the bed bugs. However exterminators rely heavily on chemical but there aren't many effective chemicals available. Therefore, I think an integrated approach would make more sense.

Many people know how to isolate the bed but don't really understand the importance of it. The most effective way of preventing them from laying eggs is to not let them bite you. Without blood meals, they simply can not reproduce. If you can manage to be bite free at least a few weeks before and after the extermination, I think your chance of success will be greatly improved. By protecting yourself, you effectively cut off their food supply and control their population. In my opinion, this is better than any growth regulator.

I believe the importance of caulking is also under estimated. To prevent them from going into the wall and spreading to your neighbors, the best thing to do is caulking. Any gaps can be sealed, but you have to be thorough, persistent and creative. If you caulk thoroughly, I think you can eliminate the most population without using any pesticides, and more importantly, the remaining ones will have no hiding places and have to come out in the open. Then with some Diatomaceous Earth (more on DE in the future) and chemical, extermination will be a lot easier.

Simply put, my strategy is to control their population by protecting myself, caulk the whole place to eliminate their living spaces and prevent them from escaping the insecticides and spreading to the neighbors, drive them out and keep them running with some chemical if necessary, and kill them through mechanical action with DE.

My first encounter with bed bugs

2006-10-12T15:06:00.000-05:00

The purpose of this Blog is to provide the people who are currently battling bedbugs some information and knowledge that I gathered from the Internet and that I gained from my own experience. Since some of them are my personal opinions, you are more than welcome to make a comment or correct my mistakes.

Bedbugs are spreading rapidly in North America, and according to some pest control experts, in five years they will be more common than mice and roaches. I regard this as a war, a war that many of us are fighting and many more will be fighting soon, so let's help each other and fight it together, and hopefully we will prevail eventually.

I'll start with my story. I moved into this bachelor apartment in Toronto on Aug 1, 2006. About three weeks after I moved in, I started to get red bumps on my feet and legs while I was at the computer, and then more on my arms and shoulders after I woke up in the morning. In less than a week, I had almost 3 dozens of these bumps. They were like mosquito bites and were itchy like crazy. But I simply didn't see anything.

I sprayed Off and Raid first, but to no avail. Then I tried Creepy Crawly, which did help, but still didn't eliminate the problem. What bothered me the most was that I couldn't identify the cause of the problem. I eventually went to my family doctor for help, who suggested that I had been bitten by bedbugs. I was shocked but still wasn't convinced since I didn't see anything until Sep 2, when I caught a nymph in my bed. Since I bought both the bed and the computer desk from Ikea after I moved in, and didn't have any second hand furniture or clothes, I was quite sure that the bugs were in the apartment before I moved in. To make things worse, my parents also found an adult bedbug in their apparent, apparently it was me who brought the bedbug to their place. Luckily they haven't been bitten so far. After extensive research on the Internet, I realized that these suckers were extremely difficult to get rid of, so I decided to move out. I wasn't required to sign a lease so I just gave the landlord a 60-day Notice to Terminate Tenancy.

I had a few nights of good sleep after I put the mattress in a zippered cover, wrapped the bed legs in sticky tape and caulked the crevices and joints in the bed frame, until I caught another nymph on my blanket. This time I called the landlord and requested an exterminator, but he wasn't willing to do so until I called Toronto Public Health for help. Finally a technician from Orkin PCO Services came and sprayed some aerosol for no more than 15 minutes. As I expected, the problem persisted, and soon I got bitten again. Now I even have sticky tape on the chair legs. I haven't been bitten for a while but I am quite sure the bugs are still around. What worries me the most is that there is a good chance that I could carry the bugs with me to the new place as many others did.