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Do Residuals Really Kill Bed Bugs?

Tuesday March 5, 2013

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Mr Pest Control

Question:

Have you come across peer-reviewed research journal articles testing the so-called residual effect chemicals have on bed bugs? I understand the dust and DE residual effect if bed bugs walk through this, but have a harder time wrapping my mind around chemical solutions having a residual effect. As far as I know, bed bugs aren't thigmotropic in the true sense as are some species of cockroaches. Ideas?

Mr Pest Control

Answer:

Let's address this in 2 parts, the first being the habits of The Common Bed Bug. I will take some passages from the great book "Bed Bug Handbook" by Pinto, Cooper, and Kraft, which is must reading for anyone who wants to be successful in controlling this difficult pest. They state here that bed bugs "prefer' to "cluster in narrow cracks and crevices made of rough material and prefer dark areas". They "prefer to squeeze together shoulder to shoulder inside a harborage site, packed together along with their droppings, shed skins, eggs, and debris". And, they typically spend more than 90% of their life within such a tight harborage. 


So, in this respect, while they may not necessarily be labeled as thigmotropic, a behavior in which they like the feel of surfaces above and below, they certainly are closely tied to these same kinds of tight crevices and companionship. It also may be the case that some individuals will be found long distances from the food source and hiding by themselves, so these also need to be sought out and that location treated in some manner (vacuum, heat, steam, insecticide, freezing). 

Since the great majority of the bugs will be hiding in crevices, holes, and voids, and up to 80% of them as close to the food source (the sleeping people) as possible, this does give us the opportunity to treat them directly with insecticides. It has been shown pretty conclusively that this bed bug has developed resistance to many of the current insecticide active ingredients, and as one researcher stated it the common bed bug appears to have the ability to quickly develop resistance to most chemicals. But, "resistance" is not "immunity", so our active ingredients will definitely kill the bugs if we have two things going for us - contact time and a sufficient level of the active ingredient. 

I don't know if they were "peer reviewed" research articles so much as reports of research done by our many university consultants, but here are some of the findings that I remember. On dust insecticides, first of all, boric acid dust is INeffective on bed bugs. Since it must be ingested to kill an insect, and bed bugs have no mechanism for ingesting dust, boric acid does not work. It is not a desiccant dust, as is often stated on the internet. The researchers, in this case, found Tempo Dust to be their top performer, killing "all bed bugs from both non-resistant and resistant populations within 24 hours". That is a pretty good testimonial from an unbiased source. DeltaDust was also effective but took longer. They also found that Drione (silica gel plus synergized pyrethrum) killed 100% of the bugs but took 72 hours to do so. Diatomaceous Earth also killed 100% but took 10 days. 

So, dusts work great where they can be applied, and since the bed bug is not moving in and out of its hiding place on a daily basis, but only when it gets hungry, applying a dust to its harborage should keep it in contact for a long enough period of time. The next part comes only from memory, but one respected researcher recently compared various active ingredients to see how well they killed bed bugs and the length of time needed. She found that essentially all active ingredients were effective eventually, but in some cases required up to 30 days of constant exposure to kill all of the bed bugs in the test. At a minimum it took probably 24 hours. This points out dramatically why applying liquid insecticides as "baseboard" treatments to exposed surfaces is unlikely to have any positive results. The fast-moving bugs simply run across the treated surface too quickly to absorb any significant amount of the active ingredient. 

But, insecticides definitely do have extended residuals. Suspend Polyzone is now claimed by the manufacturer to last up to 3 months. Microencapsulated formulations will last for many weeks, particularly when placed into the hidden places where they are not affected by physical removal, light, etc. These also tend to reduce or eliminate any repellent effect, helping to keep the hidden bugs in that place and in contact with the a.i. Many PMP's add some synergized pyrethrum to a mix of a residual product and report good results. Perhaps this is from the quick knockdown from the pyrethrum or perhaps the synergist is helping to overcome resistance to the residual a.i. Pyrethrum alone ought to be pretty repellent. So, don't stop using residual liquid materials, but use them only where they provide the best chance of creating a long contact time with the bugs, and use other non-chemical tools as part of the overall program. 

Mr. Pest Control

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Please note, Mr. Pest Control is answering questions supplied by PMP customers across North America. His answers are generated from industry and manufacturer-provided information. The answer may not be specific to the laws and regulations for your State, Province, Territory or Country. In addition, products mentioned may not be registered and or available in all areas. Always check with your local Univar office for specific information to your area. Always read and follow label directions.

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