Abundance and Species Diversity of Thrips (Thysanoptera: Thripidae) in Cotton, Soybean, and Peanut in Southeast Virginia, and Evaluation of Cyantraniliprole for Thrips Management

Abstract

Thrips are major agricultural pests throughout much of the United States. More information is needed about sampling methods, management practices, and insecticide susceptibility to help better control this pest. A two year survey was conducted to determine the species present in southeast Virginia and the population characteristics of those species. Thrips were monitored using yellow sticky traps. Tobacco thrips, Frankliniella fusca, were the most abundant species. In general thrips populations began to build up beginning in April, peaked in August, and then started to decline. Differences in this trend were observed between species. A study was conducted in seedling soybean to evaluate the within-plant location of thrips, whether a plant subsample could be used for thrips monitoring, and to determine the thrips species complex present. Soybean thrips, Neohydatothrips variabilis, were the most prominent species present. The greatest density of thrips larvae was located in the terminal bud of the seedling and suggests that immature thrips aggregate. Neither of the proposed subsamples of plant material explained the variability in immature thrips numbers and at this time we recommend whole-plant sampling for obtaining the most accurate estimate of thrips populations in seedling soybean. Tobacco thrips, F. fusca, as well as a complex of other thrips species attack cotton and peanut seedlings and can cause significant yield loss to these crops in the mid-Atlantic U.S. Experiments were conducted in these two crops to assess the efficacy of a novel diamide insecticide cyantraniliprole applied as a liquid in-furrow at planting and post-plant emergence broadcast spray treatment to control thrips. In both cropping systems cyantraniliprole significantly reduced the number of immature thrips and reduced thrips feeding injury to the plants. In several instances cyantraniliprole treatments resulted in increased yield as compared to the non-insecticide treated control and yields which were statistically similar to those obtained with standard thrips control insecticides. Laboratory bioassays were conducted to evaluate the toxicity (LC50 values) of cyantraniliprole and two conventional insecticides against F. fusca adults. Results of these assays were inconclusive. At times F. fusca adults were susceptible to the insecticides, but the results could not be replicated consistently.