Soybean gall midge: Understanding larvae abundance on soybean plants during the growing season

Soybean gall midge (SGM) Resseliella maxima Gagné was described in 2018 as a new species and it is currently considered a serious pest of soybean in the Midwest. SGM injury to soybean plants is caused by its three larval instars feeding inside the stem, primarily at the base of the plant. Plants infested with SGM exhibit a darkening of the stem, disrupting nutrient flow within the plant and can lead to wilting and death of plants. Significant yield losses have been recorded, however, these losses are often confined to the field edge. A study was conducted to determine larval abundance of SGM on soybean plants from overwintering adult emergence throughout the remainder of the season. Ten plants with signs of SGM infestation were pulled out of the field three times per week from two soybean fields in eastern Nebraska. Stems were dissected, and the larvae were separated by instar and counted. Adults were first detected in cages near both soybean fields on June 13. Larvae were first observed in plants on June 17 and 18. Data collection is ongoing, and it will continue through the remainder of the season. Results will be interpreted through a descriptive statistical analysis. Tracking the larval population over time will provide a better understanding on the efficiency of adult emergence cages, as well as identifying the appropriate sampling time to evaluate the impact of insecticides on larval population. These results will also contribute important information on the biology and ecology of this pest.