Predaceous arthropods and pests were monitored throughout the season in large plots of conventional and Bollgard cotton that were untreated and treated in the early season with applications of organophosphate insecticide that mimic treatment for early season pests (1999 and 2000). Cyhalothrin was applied as needed for bollworm (Helicoverpa zea [Boddie]) control in disrupted plots of conventional cotton and spinosad (Tracer) was utilized in a similar way in B.t. plots. Spinosad was also applied to previously untreated conventional plots. Applications of broad-spectrum insecticides to conventional or B.t. cotton prior to the bollworm flight caused significant reductions in populations of predators (ants [Solenopsis sp.], geocorids [Geocoris sp.] and spiders). This resulted in higher numbers of H. zea later in the season that required increased insecticide application for control compared to plots that were untreated early. Bollgard II cotton, which expresses both Cry1Ac and Cry2Ab proteins, was incorporated during 2001 and 2002. Plots were arranged in four main blocks: untreated, acephate treated in early season, spinosad treated for bollworm, and cyhalothrin treated for bollworm. Applications of organophosphates in early season again reduced populations of predaceous arthropods, some of which did not recover during the rest of the growing season. This resulted in significantly higher populations of bollworms in conventional and Bollgard plots. In Bollgard II plots, populations of H. zea remained below economic levels whether predators were disrupted or not. Cyhalothrin treated plots of conventional and Bollgard cotton had lower populations of predaceous arthropods than spinosad treated plots.
Species 1: Lepidoptera Noctuidae Helicoverpa zea (bollworm)
Keywords: Predation, Bollgard cotton
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