Impact of hilling timing on soybean gall midge (Diptera: Cecidomyiidae) abundance, plant injury, and yield.

In 2019, the soybean gall midge (Resseliella maxima Gagné) was identified as a new pest and species in the US Midwest, causing injury to soybean (Glycine max (L.) Merr.). Infestation of R. maxima in soybean starts with females laying eggs in the fissures or cracks that develop at the base of soybean at the V2 growth stage. These fissures can be found on soybean from the soil surface to the cotyledonary node. After eggs hatch, larvae feed inside the stem, leading to wilting and death of the plants. In 2021, hilling was tested as a cultural tactic at the V2 stage, where soil was placed at the base of stems covering the fissures, resulting in a reduction in soybean gall midge infestation. To better understand this cultural control practice, hilling was performed at different timings at different vegetative (V2, V5) and reproductive (R2) soybean growth stages during the 2022 and 2023 growing seasons. We hypothesized that a greater abundance of larvae and increased plant injury would occur with later hilling applications. The results showed that soybean hilled at V2 and V5 stages had a lower infestation and higher yields compared to hilling later. The results of this study demonstrate that hilling during vegetative growth stages can reduce R. maxima infestation and prevent yield loss.