The Vidalia onion crop in Georgia is grown in the winter, and the key insect pests in Georgia are thrips (Thysanoptera: Thripidae). The thrips complex consists predominantly of tobacco thrips, Frankliniella fusca (Hinds), with smaller percentages of western flower thrips, F. occidentalis Pergande, eastern flower thrips, F. tritici (Fitch) and onion thrips, Thrips tabaci Lindeman. Onion thrips has become a greater concern in the last 10 years likely due to the introduction of a more aggressive biotype of T. tabaci on onions coming from Peru into the Vidalia region. A preliminary laboratory bioassay at 25 °C suggested that this onion thrips biotype could out-compete tobacco thrips on onions. Surveys were conducted from 2004 through 2013 in commercial Vidalia onion fields to determine if this increase in the percentage of onion thrips would occur. Average seasonal temperatures were highly correlated (r = 0.811) with percent T. tabaci and negatively correlated (r = -0.807) with F. fusca. The results suggest that temperature might regulate the proportion of onion thrips to tobacco thrips in the field, with a higher percentage of tobacco thrips occurring during cool winters and more onion thrips occurring in warm winters. Nevertheless, F. fusca continues to be the dominant thrips species in the Vidalia onion winter growing region of Georgia averaging 78% of the adult thrips population from 2004 to 2013.
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Vol. 97 • No. 2