Population Dynamics and Within-Plant Distribution of the Western Flower Thrips (Thysanoptera: Thripidae) an Early-Season Predator of Spider Mites Infesting Cotton

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Abstract
The season-long population dynamics and within-plant distribution of the thrips Frankliniella occidentalis (Pergande) were examined. Thrips density was highly variable and peaked in midseason. Fluctuations in density in combination with changing age structure of the population suggest that migration plays an important role in the population dynamics of thrips. The seasonal peak in thrips density corresponded with the period of peak bloom. Adult thrips were strongly attracted to cotton flowers, which suggests that the migratory nature of thrips is in part caused by their preference for flower structures. Within-plant distribution of thrips on mainstem node leaves is broad and largely overlaps that of spider mites, Tetranychus spp., a prey of thrips in early-season cotton. The combined mainstem and branch node distribution of thrips shows that during most of the season, thrips are centrally located in the plant canopy.