Frankliniella fusca and Frankliniella occidentalis response to thrips-active Cry51Aa2.834_16 Bt cotton with and without neonicotinoid seed treatment
2020
D'Ambrosio, Damon A. | Kennedy, G. G. (George G.) | Huseth, Anders S.
Frankliniella fusca (Hinds) and F. occidentalis (Pergande) are economically important thrips species in cotton production. In the Southeast and Mid-South, F. fusca is an early season seedling pest. In the West, F. occidentalis is a sporadic pest of seedling cotton and a predator of other cotton pests. A novel Bt toxin, Cry51Aa2.834_16 expressed in MON 88702 cotton, has activity against thrips and plant bugs, and will likely become an important management tool for early season pests in cotton. Determining its utility in cotton pest management requires understanding its effects on F. fusca and F. occidentalis.Individual adult female F. fusca and F. occidentalis were exposed to cotyledon disks cut from greenhouse-grown cotton expressing Cry51Aa2.834_16 (MON 88702) or a near-isoline (non-Bt) with or without an imidacloprid seed treatment. Insects were exposed for 72 h and mortality evaluated. Next, individually caged seedlings were infested with five adult female F. fusca or F. occidentalis and egg numbers counted after 72 h. Larval establishment determined after 10 days for F. fusca or 7 days for F. occidentalis.Exposure to MON 88702 in the absence of the imidacloprid seed treatment caused significant adult mortality in F. occidentalis. Exposure to the imidacloprid seed treatment caused significant adult mortality in both species on both MON 88702 and non-Bt cotton plants. Oviposition and larval establishment were reduced by both MON 88702 as well as imidacloprid seed treatment in both species, but the effect size differed between species. In F. fusca, the imidacloprid seed treatment caused the greatest reductions, whereas in F. occidentalis, MON 88702 had the greater effect.
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