August 13, 2009

Insect circadian rhythms are studied

U.S. scientists say they've found some insects' circadian rhythms can be used to make them more susceptible to pesticides at certain times of day.

Researchers at Oregon State University said their finding might make it possible to identify the times a target insect is most vulnerable to a specific pesticide, and use that information to increase the effectiveness, reduce costs and decrease the amounts of pesticide necessary for insect control.

We found that it took triple the dose of one pesticide to have the same lethal effect on fruit flies at the time of day their defenses were strongest, compared to when they were weakest, said Louisa Hooven, a postdoctoral fellow and lead author of the study. A different pesticide took twice the dose. This makes it pretty clear that the time of day of an exposure to a pesticide can make a huge difference in its effectiveness.

The researchers said circadian rhythms appear to coordinate xenobiotic metabolizing genes, or the genes responsible for breaking down and detoxifying various poisons, such as pesticides.

This rhythmic defense mechanism may have evolved in order to disarm the noxious compounds that plants produce to avoid being eaten by an insect, said Professor Jadwiga Giebultowicz, who led the study.

The research that also included undergraduate students Katherine Sherman and Shawn Butcher appears in the online journal PLoS One.