Developing an injury severity to yield loss relationship for soybean gall midge
Soybean gall midge, Resseliella maxima Gagné (Diptera: Cecidomyiidae), is a new pest recently confirmed on soybean, Glycine max (L.) Merr. (Fabales: Fabaceae). Found only in Nebraska, Iowa, South Dakota, Minnesota, and Missouri, soybean gall midge infestations have caused severe economic loss to commercial fields beginning in 2018. Much is still unknown about this pest, so our research efforts have been focused on understanding applied biology and management. We developed an injury rating system to quantify the severity of plant injury from soybean gall midge larvae. Research plots from 2019 and 2020 in Iowa and Nebraska were evaluated for injury throughout the growing season and yield was measured. Our objective was to describe the relationship between injury severity and yield loss caused from soybean gall midge. A nonlinear regression model was developed to validate our injury rating system and to express the relationship between season long injury severity and yield loss. Results from our analysis indicate the injury rating system developed correlates well with yield loss caused by larvae and may be an important tool for understanding the economic impact of this emergent pest of soybean.