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Soybean Gall Midge Update in North Dakota (06/24/21)

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Soybean gall midge, Resseliella maxima, is a new insect pest, which has been confirmed from Minnesota, Nebraska, Iowa, South Dakota, and Missouri. However, soybean gall midge has not been detected in soybeans grown in North Dakota in spite of intensive survey efforts. See the 2020 soybean gall midge survey map.

Adults are small mosquito-like flies and hard to see in the field. They are light to dark brown, about ⅛ inch in body length with an orange abdomen. Their characteristic markings are the white and black banding on the antennae and legs, and mottled wings (Figure 1). Young soybean gall midge larvae (Figure 1) are white and very small, whereas the mature larvae are orange to reddish orange and about 1/12 inch in length.

Soybean gall midge larvae feed beneath the epidermis near the base of the stem (Figure 1). Sometimes the base of the stem is necrotic (dark coloration), swollen, deformed and gall-like. Heavily infested soybean plants are stunted, wilted, lodged or dead. Significant yield losses at field edges have been recorded in states with severe infestations.

Figure 1. Left photo - Adult femail and male gall midge; Middle photo - Larvae in soybean stem; right photo - dark discolorations from soybean gall midge feeding injury at the base of soybean stems

When you scout for soybean gall midge, look for the larvae in stems and stem injury. Adult flies are too difficult to observe. Walk a transect in the first four rows near the field edge, especially in areas where dense vegetation occurs along the field edge. Examine 10 consecutive plants at 10 sampling sites per field (total of 100 plants per field). Sampling sites should be spaced more than 50 feet apart. At each sampling site, examine plants for the presence of necrosis and brown or dark discoloration at the base and lower portion of each stem. If necrosis is observed, pull up the soybean plant and peel back the outermost layer of the stem on the necrotic area to look for small white or orange larvae.

Currently, soybean gall midge adults are emerging in Minnesota, South Dakota, Iowa, and Nebraska. We encourage you to look for soybean gall midge when scouting your soybean fields. Please let us know if you happen to see any tiny white to orange larvae in lesions at the base of the stem. To confirm its identification, collect more than 10 larvae and place them in alcohol vials or collect two infected plants with larvae and put them in a plastic bag. Send collected samples to your local county Extension agent or to NDSU Extension Entomology for further identification.

For more information, please see the new NDSU Extension publication on Soybean Gall Midge and White-mold Gall Midge in Soybean (E2006, Dec. 2020). Thanks to the support from the North Dakota Soybean Council.

Veronica Calles-Torrez, Postdoctoral Scientist

Janet J. Knodel, Extension Entomologist