2nd Place: Planting date and an at-plant insecticide as management strategies for soybean gall midge

Soybean gall midge (SGM), Resseliella maxima Gagne was recently identified as a new species in the Midwestern United States that is causing injury to soybean. It has been found in five states (NE, MN, SD, IA, and MO) and can cause up to 100% yield loss in soybean for the first 30 meters from the field edge. Field and greenhouse observations have shown that SGM infests soybean through fissures at the base of the plant that appear at the V2 stage. Since plant stage is an important factor for infestation, and little is known about chemical control for this pest, a field study was conducted in four locations in eastern Nebraska to evaluate the impact of planting date in combination with an at-plant insecticide (Thimet) on SGM infestation and plant injury. The experiment was conducted as a randomized complete block split-plot design with three planting dates (late-April, mid- and late May) as the main plot, and a split-plot treatment with or without an at-plant granular application of Thimet (a.i.: phorate; 9 oz/1000 ft-row). To evaluate the impact of these tactics on SGM, the frequency of infested plants, larval abundance, plant injury score, and yield were recorded. Results showed a significant difference in larval abundance, plant injury, and yield between treatments. However, these differences varied between sites. This study provides a better understanding of SGM management through the use of a combination of strategies to help mitigate plant injury from this new and challenging pest problem.