EARLY-SEASON INCIDENCE OF THRIPS (THYSANOPTERA) ON WHEAT, COTTON, AND 3 WILD HOST-PLANT SPECIES IN SOUTH-CAROLINA

Wheat (Triticum aestivum L.) and cotton (Gossypium hirsutum L.) in five counties in northeastern South Carolina (Darlington, Dillon, Lee, Marlboro, Sumter) were surveyed for thrips (Thysanoptera) during the spring 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), Frankliniella tritici (Fitch), F. occidentalis (Pergande), F. fusca (Hinds), and Haplothrips graminis Hood comprised ca. 98% of the adult thrips on wheat during both years. Frankliniella occidentalis was predominant on cotton during both years, comprising ca. 68 and 89% of the adults during 1991 and 1992, respectively. Frankliniella fusca and F. tritici accounted for ca. 26 and 3% respectively, of the adults during both years. Frankliniella occidentalis was predominant on the three noncultivated hosts, comprising over 93% of the thrips collected from each of these hosts during both years. Thrips densities were much greater on wild mustard than on toadflax and sorrel. Nine additional species of thrips were collected during this study. Densities of immature thrips were high on wheat, cotton, and wild mustard. This study indicates that wheat and wild mustard may be important reservoirs for thrips populations which subsequently migrate to cotton.