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Soybean Gall Midge (07/25/19)

The soybean gall midge, Resseliella maxima (Gagné), is a new species that was recently described by Gagné et al. (2019, Proc. Entomol. Soc. Washington 12: 168-177).

The soybean gall midge, Resseliella maximaent.9 (Gagné), is a new species that was recently described by Gagné et al. (2019, Proc. Entomol. Soc. Washington 12: 168-177). This is a new insect pest of soybeans. Its origin has not been determined. Soybean gall midge has been recorded in soybeans in Nebraska, Iowa, South Dakota and Minnesota in 2018, and in Missouri in 2019.

It has not been detected or confirmed in North Dakota yet. Currently, we are conducting a survey for the soybean gall midge, especially in southeastern ND. All fields were negative for soybean gall midge last week. If you see any suspected plants with soybean gall midge in ND, please let me know. Thanks to the ND Soybean Council for support.

Identification:  The soybean gall midge belongs to the insect family Cecidomyiidae and is about ¼ inch long, with black and white banding on legs and reddish abdomen. There are 15 known species within the genus in North America, and 55 species worldwide. Some midge species are gall formers, and others are fungus feeders or even predacious on insects. Two other Cecidomyiid pests of ND crops are the Hessian fly and the wheat midge.

Life Cycle:  Soybean gall midge has complete metamorphosis (egg, larva, pupa and adult). They probably overwinter as larval cocoons in the soil, similar to wheat midge. Entomologists have recorded multiple generations per season in Nebraska, but are uncertain on number and timing. In 2019, adult emergence of the 1st generation ranged from mid-June in Nebraska through early July in Minnesota. The adult has a long emergence window which could make insecticide control difficult. Larvae were observed in soybean stems from late June though July in Minnesota.

Crop Damage is caused by the larval feeding inside the stem, which causes brittle stems and significant yield losses when populations are high. Midge larvae feed under the epidermis of the stem, weakening the stem and causing lodging, which further adds to the yield losses.

Scouting:  This is an easy insect to scout for since infestations are most likely on field edges and adjacent to infested soybeans from last year. Walk along the field edges and look for plants with a darken stems at the base near the soil level. The feeding injury is visible after the V2 stage for soybeans. If you peel back the stem epidermis with your fingernail, the larva will be visible. Early instar larvae are white and more mature instar larvae are orange to red. Entomologists are not sure how the larvae get into the stem, maybe from naturally occurring cracks in epidermis or other wounds like hail injury. Soybeans with severe feeding injury will wilt and die. Lodging at soil level is also a symptom of heavily infested stems with soybean gall midge larvae.

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Janet J. Knodel

Extension Entomologist

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