Sampling the tobacco farmscape for thrips vectors of tomato spotted wilt
The plant species (weeds and volunteer crop plants) present in the tobacco farmscape were sampled for thrips (tiny insect pests in the family Thripidae) during January through May in 2007-2009, to determine thrips abundance, reproductive capability, and species composition. Nearly 10,000 adult thrips were collected and identified during this three year study. The tobacco thrips, Frankliniella fusca, was the most common thrips vector (insect pest that is capable of transmitting a pathogen) present in the farmscape, and was collected from 19 of the 24 host plants observed in the farmscape. F. fusca were most numerous on wild radish, nutsedge, cutleaf evening primrose, rye cover crop, and volunteer soybeans. The western flower thrips, F. occidentalis, another vector of tomato spotted wilt, also was commonly collected from 16 of the host plants in the farmscape, but overall numbers were much lower than for F. fusca. Western flower thrips were most common on wild radish, vetch, clover, nutsedge, and rye cover crop. Other thrips species were commonly found on all 24 of the plant hosts in the farmscape, and most commonly observed on clover, broomsedge, rye cover crop, wild radish, and honeysuckle. The tobacco thrips was the predominant thrips species on tobacco foliage while the nonvector flower thrips, F. tritici, was the predominant thrips on tobacco blooms. Thrips vector species were collected every month of the survey, and were most abundant during March through May. Most plant hosts also were suitable for thrips reproduction and development as evidenced by the large numbers of immatures observed. It is apparent that numerous plant hosts are available in the tobacco farmscape to maintain spotted wilt innoculum and thrips densities during the winter and early spring months.