Reitz: Distribution of Thrips in Tomato 431 SEASONAL AND WITHIN PLANT DISTRIBUTION OF FRANKLINIELLA THRIPS (THYSANOPTERA: THRIPIDAE) IN NORTH FLORIDA TOMATOES

Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) , the western flower thrips, is the primary insect pest of tomatoes and other vegetable crops in northern Florida and the rest of the southeastern USA. However, it is not the only flower thrips present in the region nor is it always the most abundant species. To determine the seasonal and within plant distribution of these various Frankliniella species, experimental tomato plants, grown under different nitrogen fertilization regimes, were sampled during the fall and spring growing seasons. Contrary to expectations, different levels of nitrogen fertilization did not affect the abundance of thrips species. Thrips were much more abundant in the spring than in the fall. In the spring F. occidentalis was the most abundant species, while in the fall F. tritici (Fitch) was the most abundant species. In both the fall and spring, significantly more adults occurred in flowers in the upper part of the plant canopy than in flowers in the lower part of the plant canopy. The sex ratio tended to be female biased, but with a greater percentage of males occurring in the upper canopy flowers. In contrast, significantly more immature thrips occurred in the lower part of the plant canopy than in flowers in the upper part of the plant canopy. Differences in seasonal patterns and within plant distribution should be considered in developing sampling protocols and management plans for thrips.