Knowing how to dis-infest clothing is important to pest control, because, as the authors so carefully explain, bedbugs "may seek harborage among clothing stored close to the bed, or may be entangled with bed linen while it is being changed. " And, "once associated with clothing or linen, there is a risk that bed bugs may then escape insecticide treatments, and may be transported to new locations."
Although there have been many recommendations on the Internet and in print concerning how to dis-infest laundry, Naylor and Boase point out that such recommendations are often vague or conflicting and have been based on little formal research. So they set out to look at the temperatures and conditions necessary to ensure 100% mortality of adult, nymph and egg stages of bed bugs.
To do this they took laboratory reared bed bugs and sealed them in cotton bags. These bags were then placed among sheets or in the pockets of clothing to assess mortality of standard cleaning methods. The results were enlightening and should help in recommendations for how your customers can ensure maximum effectiveness of methods to disinfest household articles.
A summary of the results of this study include the following:
- Freezing can kill bed bugs. Reducing temperatures to -17 degrees C (0 degrees F) for 2 hours will kill all bed bug life stages (about the temperature of a chest freezer, not a refrigerator freezer). A 5.5 lb batch of clothes, however, does not drop to 0 degrees F immediately. The researchers found that it took about 8 hours for the temperature in the center of that wad of clothes to killing temperature. Upshot? Put clothes in freezer for at least 10-12 hours.
- Bed bugs are also susceptible to high temperatures of 40-50 degrees C (104-122 degrees F). In order to reach these temperatures, clothing to be dis-infested can be placed in a large tumble drier at the HOT setting for at least 30 minutes (for a 7.7 lb load). A 10 minute HOT tumble dry only killed about 75% of nymphal bed bugs, 85% of adults. Interestingly, the COOL cycle killed almost no bed bugs.
- Soaking clothes in cold water for 24 hours (without detergent) killed all adults and nymphs, but killed no eggs. Unfortunately, the researchers did not test whether soaking clothes in cold soapy water for 24 hours would kill eggs. This alternative treatment might be useful, especially for cleaning clothes that are labeled for cool wash and dry only.
- Dry cleaning killed all life stages of bed bugs, and would be an appropriate treatment for delicate and temperature sensitive fabrics.
- When washing clothes, wash water at 60 degrees C (140 degrees F) on 30 minute wash cycles killed 100% of all life stages. Washing at 40 degrees C (100 degrees F) killed all adults and nymphs, but only 25% of eggs. So clearly, washing clothes for bed bug dis-infestation should be done at the hottest temperatures (about 140 degrees F).