Heat and cold treatment
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:
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 140-160oF for several hours. This is to ensure that the temperatures in the harborages are maintained above the thermal death point, which is about 113oF. 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 100oC, twice as high as the thermal death point for bedbugs, 45oC. 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:
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 100oC at standard atmospheric pressure. But while it takes 1 calorie to increase the temperature of 1 gram of water by 1oC, it requires 539 calories for 1 gram of water at 100oC 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 80oC.
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.
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 180oF, 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 120oF, 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 150oF. 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 -42oC. While natural water, which contains other substances such as minerals, dissolved gases, and organic and inorganic substances, freezes at 0oC. 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 0oF 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 0oC and a home freezer runs between -15 to -20oC.
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 0oC - 70oC, 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:
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.
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 140-160oF for several hours. This is to ensure that the temperatures in the harborages are maintained above the thermal death point, which is about 113oF. 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 100oC, twice as high as the thermal death point for bedbugs, 45oC. 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 100oC at standard atmospheric pressure. But while it takes 1 calorie to increase the temperature of 1 gram of water by 1oC, it requires 539 calories for 1 gram of water at 100oC 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 80oC.
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 180oF, 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 120oF, 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 150oF. 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 -42oC. While natural water, which contains other substances such as minerals, dissolved gases, and organic and inorganic substances, freezes at 0oC. 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 0oF 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 0oC and a home freezer runs between -15 to -20oC.
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 0oC - 70oC, 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.
posted by Frank at
1:40 PM
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