Breakthrough could mean less pesticide use by California farmers

From Central Valley Business Times:

The spotted-wing drosophila, a major fruit crop pest that wreaks economic havoc throughout the world, can be better controlled through strategic timing of insecticide applications linked to circadian activity and detoxification gene expression, according to research by University of California, Davis scientists.

Native to Southeast Asia, Drosophilia suzukii infests soft-skinned fruits such as strawberries, raspberries, cherries, blueberries and blackberries.. The insect was first detected in the United States in 2008 when scientists identified it in California’s Central Coast region.

It can cause an estimated $300 million in damage annually to California crops.

In pioneering research, a four-member team from the Department of Entomology and Nematology sought to find out the pest’s response to insecticide toxicity and whether it could be predicted through the integration of circadian activity and gene expression profiles.

“Since we know detoxification of insecticides by all insects including the spotted-wing drosophila is under the regulation by the circadian clock, that is, the same endogenous body clock that control timing of physiological phenomena such as sleep-wake cycle, we set out to examine if there is a time over the circadian day when the detoxification system will be at its weakest,” says Joanna Chiu of the UC Davis Department of Entomology and Nematology, lead author of the paper and a molecular geneticist.

“It is possible that if insecticides can be applied at the time when the SWD's defense system against insecticides is at its weakest state, they will be more effective,” says Ms. Chiu. “Results from our experiments turned out to be a bit more complicated than we originally envisioned, but we indeed found that at least for malathion, there is an optimal time for application to inflict maximum damage to SWD. We hope that growers will be able to use fewer insecticides, thereby decreasing damage to the environment and decreasing costs at the same time.”

But Ms. Chiu cautions that the scientist still need to conduct field trials to confirm their laboratory observations.

The research, published in the Public Library of Science (PLoS) and titled “Integrating Circadian Activity and Gene Expression Profiles to Predict Chronotoxicity of Drosophila suzukii Response to Insecticides,” combines the molecular biology and circadian biology expertise of the Chiu lab and the integrated pest management expertise of the Frank Zalom lab. It was funded primarily by the California Strawberry Commission.

“SWD is becoming a big problem for growers of soft-skinned fruits such as strawberries, raspberries, blueberries, and cherries all over the world,” says Ms. Chiu. “With the need to satisfy insect damage standards and to reduce crop loss, the growers generally adopt high levels of insecticide usage for SWD control and risk reduction. In the long-term, this will lead to development of insecticide resistance, not to mention the damage inflicted on beneficial insects.”

Current strategies to control the pest rely on insecticide usage, because other pest management tactics are still being developed.

“This knowledge could be particularly interesting for organically acceptable insecticides like pyrethrum that are only effective for a short period of time after they are applied,” says Mr. Zalom. “Pyrethrum is one of the only organic options that can be used by farmers to control Drosophila suzukii, so if its efficacy can be improved by applying sprays at a certain time of day then this could be a positive development.”