The jury is still out on whether Gentrol helps or makes bed bug infestations worse.

I think I can say, though, that whatever negative effects it might have would not have occurred within five days.

It is more likely that something your PCO used to treat (perhaps a flushing agent) drove bed bugs and roaches out of hiding. This does not mean their population has increased, but rather means you have a better shot at killing them. Hiding bugs do not die from pesticides. Coming out and crossing poison is the way they will be hit.

So, sorry this is unpleasant, but don’t assume the treatment was bad. If you want more feedback, come to the forums (button above). In any case, make sure your PCO re-treats in about 2 weeks.

Do you expect the study will eventually get published?

To any entos: are there other insect growth regulators that have been shown to be effective against bedbugs? Thanks in advance for any responses.

The following paper was presented at the Annual Meeting of the Entomological Society of America on 13 December, 2006: The effects of hydroprene (9%) on the common bed bug (Cimex lectularius (L.) development by David J. Moore, Dini M. Miller (VPI).

Note: the study was supported by Zoecon.

Summary of the study:

The study was targeted at third instar nymphs of bed bugs using the labeled rate of Gentrol. The third instar stage was selected because this stage was supposedly the most susceptible to the effect of hydroprene. Gentrol was applied to filter paper strips, which were placed into small glass vials containing third instar bed bugs. Three filter paper strips (one treated and two untreated) were placed into each vials for the Gentrol treatment whereas the control treatment received three untreated paper strips. After 2 weeks of continuous exposure, one untreated filter paper strip was replaced with a fresh Gentrol treated paper to mimic application recommendation by Zoecon in the Gentrol treatment.

No developmental effects were evident in the nymphs until the commencement of nymph-to-adult molt. Sixteen percent of bed bugs died during mid-molt and an additional 18% died due to incomplete sclerotization of the adult cuticle. Surviving adults were examined for morphological defects. Males exposed to Gentrol showed a 25% reduction in the length of the male genitalia and the deformation of female genetalia was also observed. Potential reproductive effect of Gentrol exposure was examined by paired crosses of the survivors (control vs. treated) by sex. Treated females mated with treated males produced ~15.3 eggs, treated males mated with untreated females produced ~11.5 eggs whereas untreated males mated with untreated females produced ~7.9 eggs. Egg viability was > 95% in all crosses. The study showed that exposure to Gentrol significantly improves the fecundity of bed bugs, and thus the effect of Gentrol on the overall level of control is actually negative.

I hope the ‘anonymous expert’ will keep us posted if this changes!