- Author: Kathy Keatley Garvey
Mohammad-Amir Aghaee, graduate student in the Larry Godfrey lab in the UC Davis Department of Entomology and Nematology, won the first-place President's Prize in his category for his 10-minute talk on a rice water weevil at the Entomological Society of America's 61st annual meeting, being held Nov. 10-13 in Austin, Texas.
His abstract: "Rice water weevils (Lissorhoptrus oryzophilus Kuschel) are the primary insect pest in California rice agriculture. They present a challenge for IPM because of their soil dwelling larvae, which prevents the effective use of parasitoids, nematodes and predators. However a possible cultural control method may present a sustainable solution if its mechanism can be explained. Data from the field experiments in the 1990s showed that winter flooding of rice fields to break down post harvest rice straw would result in reduced larval populations in the spring. Studies from the last two years have been exploring the mechanisms behind this decline. Similar results were shown in a greenhouse study in the summer of 2013, with reduced larval counts in treatments with a winter flood compared to treatments without the flood. As part of this study we also examined the addition of rice straw, which nullified the effects of the winter flood. The evidence suggests that use of winter flooding in California will have benefits for growers against rice water weevil, but the mechanism behind it has yet to be determined."
Kwok, who works closely with integrated pest management specialist/professor Zalom; doctoral candidate Kelly Hamby of the Zalom lab; and molecular geneticist Joanna Chiu, assistant professor in the Department of Entomology and Nematology, discussed "Integrating Circadian Activity and Gene Expression Profiles to Predict Chronotoxicity of Drosophila suzukii Response to Insecticides."
Native to Southeast Asia, Drosophila suzukii is a recent invader that infests ripe and ripening fruit, leading to significant crop losses. Since current D. suzukii management strategies rely on insecticide usage, and insecticide detoxification gene expression is under circadian regulation in the closely related Drosophila melanogaster, we set out to determine if integrative analysis of daily activity patterns and detoxification gene expression can predict chronotoxicity of D. suzukii to insecticides. Locomotor assays, detoxification gene expression analysis, and acute insecticide contact bioassays were performed under conditions that approximate a typical summer day in Watsonville, California, where D. suzukii was first detected in North America. Summer is also the cropping season, when most insecticide applications occur. We observed that D. suzukii assumed a bimodal activity pattern, with maximum activity occurring at dawn and dusk. Five of the six genes tested exhibited rhythmic expression over a circadian day, with the majority showing peak expression at dawn (ZT0, 6am). We observed significant differences in the chronotoxicity of D. suzukii towards malathion, with highest susceptibility at ZT0 (6am), corresponding to peak expression of cytochrome P450s that may be involved in bioactivation of malathion. High activity levels were not found to consistently correlate with high insecticide susceptibility as initially hypothesized. Chronobiology and chronotoxicity of D. suzukii provide valuable insights for monitoring and control efforts, because insect activity as well as insecticide timing and efficacy are crucial considerations for pest management. However, field research is necessary for extrapolation to agricultural settings.
The first-place President's Prize consists of a one-year free membership in ESA, a $175 cash prize, and a certificate. The second-place winner receives a certificate and a $50 cash prize.
Frank Zalom is the incoming president of the 6500-member ESA and will assume his new duties today (Nov. 13). He will president over the ESA's 62nd annual meeting, to be held next year in Portland, Ore.