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 newly published 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 the central coastal region of California. It can cause an estimated $300 million in damage annually to California crops.

In pioneering research, the 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 (SWD) 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,” said lead author and molecular geneticist Joanna Chiu of the UC Davis Department of Entomology and Nematology.

 

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“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,” Chiu said. “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.”

“We caution growers that we still need to conduct field trials to confirm our laboratory observations,” Chiu added.

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.