"Because chlorpyrifos kills in a way that is similar to many other insecticides, higher resistance may have been favored each time any insecticide was sprayed," said Pitt alumnus Jenise Brown (A&S '09), a coauthor of the study and a former undergraduate researcher in Relyea's lab. "In contrast, herbicides have a variety of ways that they kill organisms, which may make it harder for animals to be resistant when exposed to different herbicides over many years."
In a related study, published online Feb. 21 in Environmental Toxicology and Chemistry, Relyea's Pitt research team examined whether wood frog populations that were resistant to chlorpyrifos might also be resistant to other insecticides. This phenomenon, said Relyea, happens commonly in pest species when farmers switch pesticides from year to year, but little is known about how this switching of pesticides affects amphibians.
Using three commonly applied pesticides that have similar chemical properties chlorpyrifos, carbaryl, and malathionthe Pitt researchers exposed 15 populations of wood frog tadpoles to high concentrations of each insecticide. They found that wood frog populations with resistance to one insecticide also had resistance to the other insecticides.
"This has a beneficial outcome," said Jessica Hua, the lead author of the second study and a graduate student in Relyea's lab. "While it doesn't mean that pesticides are beneficial to amphibians, our work does suggest that amphibians can evolve to resist a variety of pesticides and therefore improve their survival."
As they hypothesized in the study published today, the researchers suspect that the r
|Contact: B. Rose Huber|
University of Pittsburgh