Reducing the Risks of Spotted Wilt Virus in Tobacco with Selected Thrips (Thysanoptera: Thripidae) Control Practices1

Tomato spotted wilt tospovirus (TSWV) is a major economic threat to tobacco production in Georgia. Several thrips species are reported as vectors of TSWV, and three of these species are observed on Georgia tobacco, Frankliniella fusca (Hinds), F. occidentalis (Pergande), and F. bispinosa (Morgan). This study evaluated several thrips control practices for efficacy and suppressing the incidence of TSWV. Five replicated field trials were conducted in 1999 and 2000 to examine acephate, imidacloprid, acibenzolar-S-methyl, spinosad, dichloropropene, chlorpyrifos, thiamethoxan, alone, and in various combinations, applied as preplant incorporated, tray drench, transplant water, or foliar treatments. The insecticides imidacloprid and thiamethoxan applied as a greenhouse tray drench or as a transplant water treatment, were effective in reducing the seasonal incidence of TSWV and imidacloprid was also effective in reducing thrips populations. The plant activator, acibenzolar-S-methyl, was effective in suppressing TSWV symptoms, but had little effect on thrips. The combination of acibenzolar-S-methyl with imidacloprid provided better suppression of TSWV than either product alone. Early-season foliar sprays of acephate also was effective in reducing thrips numbers and TSWV. Dichloropropene, chlorpyrifos and spinosad were not effective for thrips control or TSWV suppression. F. fusca was the predominate thrips species on tobacco foliage, ranging from 82.7–94.9% of the thrips complex. Only 4.6% and 1.2% of the thrips specimen were confirmed as vectors of TSWV in 1999 and 2000, respectively, based on enzyme-linked immunosorbent assay test results. Imidacloprid, thiamethoxan, acibenzolar-S-methyl, and acephate do provide thrips control options that can reduce TSWV in tobacco, and these materials are labeled for tobacco.