Relationships between tobacco thrips infestation and peanut yield in southeastern United States

Tobacco thrips, Frankliniella fusca, is a major pest of peanut (Arachis hypogaea) in southeastern United States. Thrips feed directly on seedling foliage, which in severe cases leads to stunted plants. At-plant prophylactic insecticides are often used, and supplementary foliar sprays will be applied when thrips feeding injury is still observed early in the season. Currently, there are no economic thresholds to facilitate tobacco thrips management, and the economic impact of this pest on peanut has not been elucidated. Field experiments were conducted to determine the relationships between thrips density and thrips injury, plant biomass, and peanut yield. Laboratory-reared thrips were released at different densities on peanut plants with three plant ages, and plants were enclosed in thrips-proof field cages. Different thrips populations were established by thrips density treatments, and higher thrips populations were found in plants infested by thrips at younger ages. Significant positive correlations were found between thrips densities and feeding injury, while negative correlations were found between thrips densities and plant biomass and pod weight. The negative effect of thrips on peanut were more often found in plants with thrips infestation occurred at younger ages. Based on significant regression models using number of thrips release as a function of peanut yield, reduction of peanut yield for individual plants ranged from 1.58 to 3.87 % per one thrips released on peanut seedlings.