Soybean gall midge: Characterizing the geographic and host plant range distribution

Resseliella maxima Gagné, Soybean Gall midge (SGM) was discovered in 2018 after the reports of  widespread early injury to soybean in Nebraska, Iowa, South Dakota, and southwest Minnesota. Heavily infested fields in East Central Nebraska have reported yield losses of 17-31%, with the majority occurring near the field border. In 2019, SGM was confirmed on sweet clover and alfalfa through genetic barcoding and morphology. This project aims to characterize the spatial and host plant distribution of SGM in Eastern Nebraska through a field survey recording larval abundance and plant injury, and their association temperature, precipitation, and surrounding crops. In 2020, infested soybean and sweet clover samples were collected from 39 counties in Eastern Nebraska using random sampling. In the border of soybean fields or roadsides, a maximum of three soybean, and sweet clover stems infested with SGM were collected per location. Adjacent fields, plant developmental stage, and injury at field border, 15 meters and 30 meters from the border, was recorded for each field. Stems were dissected, and the number of white and orange larvae per stem were counted and preserved for further studies. Results suggest continuous expansion in its geographic range over the past three years, higher injury to the soybean plants in counties with higher area under soybean plantation in Nebraska. The next steps include replicating the survey in 2021 under a shorter temporal window for better understanding and characterizing the SGM population genetic structure using mitochondrial COI gene sequence of the larvae collected in 2020 and 2021.