Capitalizing on the insect's biological clock
Insects are more vulnerable to pesticides at certain times of day
Loiusa Hooven is interested in testing the biological clock concept on cherry fruit fly.
Courtesy Oregon State University
New discoveries by Oregon State University researchers could help growers better target pesticides in the future by using circadian rhythms or biological clocks to time applications when insects are most susceptible to pesticides.
A team of OSU scientists, headed by Louisa Hooven, postdoctoral fellow in the zoology department, found that it could take as much as a triple dose of a pesticide to have the same lethal effect on an insect at the time of day when its defenses were the strongest, compared with when its defenses were weakest. For their experiments, the team used Drosophila melanogaster, a vinegar fly commonly used in research.
The different responses to the same pesticide exposure, but at different times of the day, makes it pretty clear that the time of day when the fruit fly was exposed to a pesticide can make a huge difference in its effectiveness, Hoover said in a phone interview with the Good Fruit Grower. More work is needed to further investigate the concept of using the insect’s clock to improve the effectiveness of pesticides or allow use of lower doses.
While she’s interested in doing preliminary work to see if the findings have application to cherry fruit fly, or other key agricultural pests, she needs additional funding. The original project was funded through grants from the U.S. Department of Agriculture, National Institute of Health, and the National Science Foundation.
Scientists have long known that certain genes in humans, animals, and plants are sensitive to the natural rhythms of day and night. Things like sleep, hormone production, stress, and medication effectivenesscan be influenced by the circadian clock.
The new findings show that the natural rhythms appear to coordinate other genes, like those involved in breaking down and detoxifying poisons, such as pesticides.
The scientists studied the diurnal response of drosophila to acute exposure of four classes of pesticides: propoxur (carbamate), fipronil (phenylpyrazole), malathion (organophosphate), and deltamethrin (pyrethrorid).
The OSU study found that the vinegar fly defenses against propoxur and fipronil were strongest during mid-day and weakest around dawn, dusk, or the middle of the night. The effectiveness of malathion and deltamethrin on the vinegar fly did not seem to be as strongly associated with time and day as the other two pesticides.
The timing of the first exposure of an insect to a pesticide can be critical. The researchers believe that timing exposure when the insect is most vulnerable could help prevent insects from developing resistance to particular pesticides.
The research findings were published in the scientific journal PLoS ONE and can be found at: http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0006469.