D3188: Evaluating the impact of soil applied insecticides on soybean gall midge (Diptera: Cecidomyiidae) emergence

Soybean gall midge (Resseliella maxima Gagné, SGM) has been an issue for some Midwestern soybean growers in the United States since its identification as a new species in 2019. SGM infestations are most severe on field edges with up to 100% yield loss along the first 30 meters of the field, decreasing towards the center of the field. SGM infests soybean plants through fissures at the base of the stems that appear at the V2 growth stage. Larvae feed on the xylem and phloem, causing permanent damage to the plant. Once larvae develop, they drop into the soil to pupate, and adults emerge. Different management strategies are being tested to decrease the infestation of SGM, such as hilling, foliar applications, and seed treatments. However, there are no insecticide studies that target adults as they emergence. As a result, two insecticides (dimethoate and bifenthrin) were applied separately to the soil to evaluate the impact on SGM adult emergence. Ten infested soybean stems were collected and buried in the field for each treatment. Cages were placed over the buried stems and checked every two days for adult emergence. The insecticides were applied 15 days after the stem burial, and water was added as another treatment factor after the insecticide application. Soil samples were collected at the end of the experiment to count larvae in the soil and detect on-emerged individuals through brine extraction. These results contribute to understanding the effectiveness of these products in mitigating soybean gall midge adult emergence.