Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2002
Publication Date: 9/1/2002
Interpretive Summary: Thrips are the most significant insect pests of vegetable crops in the southeastern USA. Feeding by thrips reduces the quality and yield of crops, and some species transmit a devastating plant disease, tomato spotted wilt virus. Developing effective IPM programs for controlling these pests depends on knowing when and where they will infest crops. Research conducted by a USDA scientist at the Center for Biological Control, Tallahassee, FL, has shown that thrips are much more abundant in the spring than in the fall. In addition, thrips of different ages and sexes occupy different portions of tomato plants. Adults, especially males, are more likely to be found in the upper part of tomato plants than in the lower part. In contrast, immature thrips are much more abundant in the lower part of plants than in the upper part. USDA scientists are using this information to refine sampling techniques for thrips. Better sampling gtechniques will lead to improved management programs and reductions in pesticide use in vegetable crops.
Technical Abstract: Frankliniella occidentalis, 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 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.