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In a 2-yr study, the impacts of different plastic soil mulches, insecticides, and predator releases on Frankliniella thrips and their natural enemies were investigated in field-grown peppers. Ultraviolet light (UV)-reflective mulch significantly reduced early season abundance of adult thrips compared with standard black plastic mulch. This difference diminished as the growing seasons progressed. Late season abundance of thrips larvae was higher in UV reflective mulch compared with black mulch plots. The abundance of the predator Orius insidiosus (Say) was significantly lower in UV-reflective mulch compared with black mulch treatments. Infection of plants with tomato spotted wilt virus, a pathogen vectored by Frankliniella occidentalis (Pergande), was <6%. In the year with the higher disease incidence (2000), UV-reflective mulch plots had significantly less disease (1.9%) compared with black mulch plots (4.4%). Yield was significantly higher in UV-reflective mulch (24,529 kg/ha) compared with black mulch (15,315 kg/ha) during this year. Effects of insecticides varied with species of thrips. Spinosad reduced abundance of F. occidentalis, but not Frankliniella tritici. In contrast, esfenvalerate and acephate reduced numbers of F. tritici and Frankliniella bispinosa, but resulted in higher populations of F. occidentalis. Spinosad was the least disruptive insecticide to populations of O. insidiosus. Releases of O. insidiosus and Geocoris punctipes (Say) reduced populations of thrips immediately after releases; naturally occurring predators probably provided late season control of thrips. Our results suggest that UV-reflective mulch, combined with early season applications of spinosad, can effectively reduce abundance of thrips in field-grown pepper.
Reitz et al. (Fri,) studied this question.