Impact of timing of hilling on the management of soybean gall midge

Soybean gall midge (SGM) Resseliella maxima Gagné was recently identified as a new species causing injury to soybean (Glycine max L.). As of 2021, this pest is known to occur in five Midwestern states in the USA (NE, IA, SD, MN, and MO). Infestation of soybean begins in late spring when adults emerge from the last year’s soybean field and move to the closest soybean field to lay eggs at the base of the plant where fissures occur. SGM infestation appears to be dependent on these fissures that occur at the V2 stage. These fissures are present just below the cotyledonary node, an area of 3-5 cm above the soil surface. In 2021, hilling applied at the V2 stage covered the fissures with soil resulting in a reduction in infestation and plant injury from soybean gall midge. This reduction was likely a result of preventing SGM adults from laying eggs in the fissures. To better understand the role of this management practice, hilling treatments will be applied at V2, V4, and V6 stages during the 2022 growing season. Data will be collected on larval abundance, plant injury, and yield. We hypothesize that a greater abundance of larvae and plant injury will occur with later hilling treatments. These results will provide a better understanding of the timeframe in which hilling should be applied for effective control of soybean gall midge.