EARLY-SEASON INCIDENCE OF THRIPS (THYSANOPTERA) ON WHEAT, COTTON, AND3 WILD HOST-PLANT SPECIES IN SOUTH-CAROLINA

Wheat (Triticum aestivum L.) and cotton (Gossypium hirsutum L.) in fiv e counties in northeastern South Carolina (Darlington, Dillon, Lee, Ma rlboro, Sumter) were surveyed for thrips (Thysanoptera) during the spr ing of 1991 and 1992. Wild mustard (Brassica kaber [DC.] L. C. Wheeler ), sorrel (Rumex hastatulus Baldwin), and toadflax (Linaria canadensis [L.]) were surveyed at one location in Darlington County in 1991 and in Sumter County in 1992. Limothrips cerealium (Haliday), Frankliniell a tritici (Fitch), F. occidentalis (Pergande), F. fusca (Hinds), and H aplothrips graminis Hood comprised ca. 98% of the adult thrips on whea t during both years. Frankliniella occidentalis was predominant on cot ton during both years, comprising ca. 68 and 89% of the adults during 1991 and 1992, respectively. Frankliniella fusca and F. tritici accoun ted for ca. 26 and 3% respectively, of the adults during both years. F rankliniella occidentalis was predominant on the three noncultivated h osts, comprising over 93% of the thrips collected from each of these h osts during both years. Thrips densities were much greater on wild mus tard than on toadflax and sorrel. Nine additional species of thrips we re collected during this study. Densities of immature thrips were high on wheat, cotton, and wild mustard. This study indicates that wheat a nd wild mustard may be important reservoirs for thrips populations whi ch subsequently migrate to cotton.