Biology and Ecology of Flower Thrips in Relation to Tomato Spotted Wilt Virus

Tomato Spotted Wilt Virus (TSWV) is transmitted exclusively by certain species of thrips. Because TSWV can only be acquired by larvae and transmitted by adults, it is essential to determine the ecology of these different life stages to improve management of thrips and TSWV. Furthermore, interspecific differences among vector species complicate management issues. Herein, aspects of the biology and ecology of thrips vectors of tomato spotted wilt virus are discussed and an overview of vector-pathogens interaction is given. The complex of native and adventive Frankliniella species that occur in the southeastern USA is used as a model system for comparing and contrasting species-specific behavioral attributes that affect large-scale spatial and temporal population dynamics. The common Frankliniella species in the southeastern USA include Frankliniella occidentalis, F. fusca, F. bispinosa, and F. tritici. The western flower thrips, F. occidentalis, is considered the predominant vector of TSWV, but F. bispinosa and F. fusca are also vectors. These Frankliniella species have rapid generation times, and adults are highly polyphagous. Numerous hosts may serve as sources for thrips entering tomato fields, yet tomato is a poor reproductive host. Therefore, most of the thrips infesting fields are immigrants. Consequently, thrips dispersal behavior is a key component of TSWV epidemiology. F. occidentalis is a less mobile species than either F. bispinosa or F. tritici. These interspecific differences in the activity levels of adults affect how the species colonize plants and the field efficacy of insecticides against each species. These results show the importance of understanding interspecific variation among vectors for management of TSWV. INTRODUCTION Tomato Spotted Wilt Virus (TSWV) is one of the most severe problems facing vegetable and ornamental production worldwide (Goldbach and Peters, 1994; Moyer et al., 1999). Tomato spotted wilt is an especially damaging disease in tomato, Lycopersicon esculentum. Infected plants do not produce marketable fruit, although symptoms may not be apparent until after harvest. Tomato Spotted Wilt Virus, the type species of the Tospovirus genus, is the predominant species, but other species attack tomato (e.g., Nagata et al., 1995). Management of these important plant pathogens is complicated by the behavior and ecology of the thrips that vector it and interspecific variations in those characters among thrips. In this paper, some of the attributes contributing to the pest status of different thrips species are discussed. The complex of native and adventive Frankliniella species that occur in the southeastern USA is used as a model system for comparing and contrasting species-specific behavioral attributes that affect large-scale spatial and temporal population dynamics, and interactions with Tomato Spotted Wilt Virus. This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or a recommendation for its use by the USDA. 75 Proc. 1st IS on Tomato Diseases Eds. M.T. Momol, P. Ji and J.B. Jones Acta Hort 695, ISHS 2005