The September 19, 2014 issue of PCT magazine contains a bed bug supplement entitled “Trouble Brewing for Insecticides?” The general thrust of the article is an examination of bed bug resistance to modern combination chemicals containing pyrethroids and neonicotonoids. An excellent read. One aspect of the article I particularly found interesting was an attempt to adjust the concentration of a chemical treatment to kill 80% of a given population of bed bugs. The remaining 20% were raised and the experiment was repeated. The result, after a single generation of selection, was a large increase in survivability. The author concludes “While selecting for resistance in the laboratory has been accomplished with other insects, it is unusual for a decline in susceptibility to evolve so quickly – elevating concerns for what might also be happening in the field.”
I have been noting a rapid shift in resistance to pyrethroids in field use. Over the years I have noted the bugs are getting harder to kill. Most bed bugs in Winnipeg can now easily cross a single pyrethroid residual line and survive very nicely. In recent times I have noted bed bugs harbouring in previously treated areas with no seeming ill effects – this is a relatively new development in my experience.
In one conversation I had with someone familiar with bed bug control in social housing it was noted that one particular infestation had been treated unsuccessfully for 5 years. Glue boards were placed under the bed legs of this infestation and 1000 bed bugs were caught in the first two weeks – and that is after 5 years of chemical treatments! Can you imagine, in light of the above study, what a 5 year natural selection program could do? There is a reason why insecticide resistance is growing rapidly.