Occurrence of five thrips species on flue-cured tobacco and impact on spotted wilt disease incidence in georgia

Thrips-vectored tomato spotted wilt tospovirus (TSWV) infection is a major constraint on tobacco production in Georgia. Flue-cured tobacco fields were surveyed throughout the season from 1989 to 1991 and 1996 to 1998 to determine spotted wilt disease incidence and seasonal abundance and species composition of thrips populations. Five species were commonly found that accounted for more than 95% of the 17,000 thrips collected, including Frankliniella fusca, F. occidentalis, F. bispinosa, F. tritici, and Limothrips cerealium. F. fusca, F. occidentalis, and F. bispinosa are vectors of TSWV. F. fusca was the most common foliage thrips collected during all years, except 1989, when L. cerealium was the most abundant species. During 1989 to 1991, 22 to 68% of the foliage and flower thrips identified were TSWV vector species. The 1996 to 1998 foliage collections had much higher percentages of vector species (95 to 97%). The 1996 flower samples also had a very high percentage of vector species (94%); however, the percentages were much lower in 1997 (3%) and 1998 (32%). A trend toward higher incidence of TSWV occurred during the last three seasons studied, when thrips vector species were more abundant.