The evolution of exterminator practice in relation to increased pyrethroid resistance

I questioned my chemical supplier who has 30 plus years experience in the exterminator business and he stated that before carbamates and organophosphates were banned there was no difficulty in getting rid of bed bugs. A single application was sufficient to kill the bugs. When Pyrethroids became mandated for bed bugs the same “single treatment” ideas persisted in the exterminator community and, over time, became ineffective.

In 2006 the bed bugs in Winnipeg were more or less limited to certain areas such as Manitoba Housing and the general population had never heard of bed bugs. It just so happened that an apartment block adjacent to my own apartment block got bed bugs in multiple suites at this time and, when I questioned the caretaker, found that the exterminator killed all the bugs with a single application with each suite requiring about 10 minutes of work. In retrospect that is amazing.

In 2007 when I had my first case of bed bugs the information I received from the largest exterminator in the city was that the pyrethroids would have a 6 week residual. My first case of bed bugs were all killed with a with single application of Dragnet 24175 and a second treatment was not even mentioned as an option. For my second infestation I brought in the same exterminator but he failed to get rid of the bugs on the first treatment. My exterminator felt bad about the failure and when he returned for the second treatment he stated “I wonder what I missed?” and proceeded to treat unlikely bed bug harbourages such as kitchen cabinets that had not been treated earlier. To be fair the exterminator was given an empty suite to treat which is very difficult to treat at the best of times because the bugs stayed in the baseboards waiting for a host. When I questioned the exterminator about the effectiveness of pyrethroids the response was the product was very effective.

When I began doing my own bed bug work shortly thereafter I noticed a transition of exterminators moving to retreatments at 2 – 3 weeks and I followed suit. I also noticed that all talk of 6 week residuals disappeared from the exterminator community. Some of the cases I did in these early years were very easy. A single application to a harbourage on the bottom of a couch resulted in bugs dying right on the couch and were found there dead 2 weeks later. The second application revealed no live activity whatsoever and many dead bugs littering the floor. Other cases were much more difficult and the bugs were no longer dying right on the harbourage suggesting they survived long enough to get off the harbourage. These cases had very few bugs littering the floor as the bugs managed to migrate to hidden areas before they died (or perhaps they did not die).

During these earlier years the exterminators often did not check surrounding suites for activity and relied on piecemeal approaches reminiscent of the carbamate/organophosphate days. Today the exterminator community in Winnipeg seems to have abandoned single treatments in favour of multiple treatments and is doing a much better job of addressing surrounding suites in multi family settings. Unfortunately the bed bug populations have become much more widespread and common place in that time as well. It seems the exterminators are fighting a losing battle.

Recently I was given a bed bug job and after I finished the work the customer demanded that I return again in 4 days like a competitor had promised. Of course I could not comply as I am limited to a minimum 9 day reapplication period as specified on the label for Tempo PCP 25673. It seems that at least one Winnipeg exterminator has been panicked at the lack of effectiveness of his chemical treatments and has resorted to 4 day retreatments!! I will give the benefit of the doubt to this exterminator and assume he was going to apply Dragnet pcp 24175 which does not have limitations on retreat times. Personally I think a 4 day retreat schedule, even with Dragnet, is ridiculous but it is in line with the historical trend of shortening the wait times between treatments. Other exterminators have shortened their retreat times to 1.5 weeks as well which was unheard of 5 years ago.

The interesting thing for me is how quickly exterminators are finding it necessary to decrease the wait times between retreatments. It seems obvious, to me at least, that the bed bugs in Winnipeg have shifted rapidly to the resistant end of the spectrum and the exterminators have responded with multiple treatments, shorter retreat periods, more thorough and time consuming treatments, and more emphasis on tenant cooperation – which is good.

It has taken 6 years to get from single effective treatments with an assumption of 6 week residuals to many exterminators requiring multiple treatments with 1.5 week retreatment intervals (or even 4 day retreatment intervals). I wonder where we will be in another 6 years?



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