Tomato spotted wilt tospovirus (TSWV) has become a major economic problem for tobacco growers in Georgia. Several species of thrips have been reported as vectors of TSWV. Three of these species, commonly observed on tobacco in Georgia, include Frankliniella fusca (Hinds), F. occidentalis (Pergande), and F. bispinosa (Morgan). This study examined the effectiveness of several thrips management practices on controlling thrips populations and suppressing the incidence of TSWV. Replicated field plots were used to evaluate aldicarb, acephate, imidacloprid, acibenzolar-S-methyl, spinosad, thiamethoxan alone and in combination, applied as pre-plant incorporated, tray drench, transplant water or foliar treatments. The insecticides imidacloprid (Admire® 2F or Provado® 1.6F) and thiamethoxan (Platinum 2® SC), applied in the transplant water or as a tray drench, were effective in reducing the early-season thrips populations and reducing the seasonal cumulative incidence of TSWV. These two products also were effective in reducing the seasonal mean population of tobacco aphids, Myzus nicotianae. The plant activator, acibenzolar-S-methyl (Actigard®), was effective in suppressing TSWV symptoms, but had no effect on thrips and minor impact on aphid population densities. The combination of acibenzolar-S-methyl with either imidacloprid or thiamethoxan provided better suppression of TSWV than any of the products alone. Acephate in the transplant water plus four early-season foliar sprays also was effective in reducing thrips numbers and TSWV incidence. Aldicarb and spinosad were not effective for thrips control or TSWV suppression. Acephate and aldicarb were effective in reducing aphid populations, but spinosad was not. Frankliniella fusca was the predominate thrips species at all test sites, ranging from 90 to 98% of the thrips complex. From 1.9 to 4.6% of the thrips collected were confirmed vectors of TSWV, based on ELISA test results. Imidacloprid, thiamethoxan, acibenzolar-S-methyl, and acephate provide thrips management options that can reduce the tobacco production losses associated with TSWV.
3Cooperative Extension Service, Georgia Southern University, P. O. Box 8112, Statesboro, GA 30460-8112.
4Department of Plant Pathology.