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How to identify it
- Adults are delicate, slender flies only about 1/8 inch (2 to 3 mm) long, with mottled wings, an orange abdomen and long legs banded in alternating light and dark.[2][1][3]
- You will rarely see the adults: they are hard to see with the naked eye and hard to catch with a sweep net.[1][3]
- The larvae are small, legless maggots. Young ones are clear to white and turn bright orange as they mature; the orange third-stage larvae are about 1/12 inch long.[2][1]
- Infested plants show dark discoloration at the base of the stem, below the cotyledon (seed-leaf) node. Peeling back the darkened skin may reveal the white or orange larvae.[1][3]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Larvae of other insects | The first two larval stages are white and can be confused with larvae of other, non-pest insects. The orange third-stage larvae are the more telling sign of soybean gall midge.[1] |
Where it lives
It was described after widespread early-season injury in soybean fields in eastern Nebraska, eastern South Dakota, western Iowa and southwestern Minnesota. By 2020 it was known from 114 counties in five states, and by April 2024 researchers had confirmed it in 164 counties in seven states. Missouri first found it in 2019, in the far northwestern counties of Atchison and Holt.[1][3]
Biology and life cycle
Larvae spend the winter in the soil of last year's soybean fields, probably inside silken cocoons, and pupate in late spring. Adults start emerging in early to mid-June, and emergence stretches over several weeks, sometimes into July.[1][2][3]
Females lay eggs at the base of soybean plants, and the larvae enter the stems. Small natural cracks at the base of the stem, below the cotyledon node, seem to be needed for egg laying, and wounds from hail or other injury may also let eggs or larvae in. Plants that have not reached the V2 stage when the first adults emerge are unlikely to be infested.[3][1][2]
Larvae appear in plants 7 to 10 days after the first adults emerge, and orange larvae about 12 days after. After three larval stages they drop to the ground, burrow into the soil and spin silken cocoons. Based on field observations, the whole life cycle takes an estimated 28 to 32 days.[1]
Nebraska recorded two complete generations in 2019 and possibly a third, and Minnesota has at least two adult generations a year. Adults do not feed, but they need water, and researchers suspect the dense vegetation along field edges supplies it.[1][2]
Larvae have also been found in sweet clover and alfalfa, more often in sweet clover; in alfalfa they usually live in the pith of the stem. Nebraska Extension advises against treating these plants to control the midge; their role in later soybean infestations is not known.[1][3]
Natural enemies may attack it, but none have been documented.[2]
Damage and signs
- Larval feeding blackens the base of the stem. Heavily infested stems become deformed, dead (necrotic) and brittle and can lodge or snap near the soil, and plants may be stunted, wilt and die. Wilting or dead plants can show up about 21 days after a heavy infestation starts.[2][1][3]
- Injury is worst along field edges next to fields that grew soybean the year before, especially edges lined with trees, shrubs, uncut brome or other dense vegetation, and near waterways. Early-planted soybean is affected most often.[1][3]
- In one heavily infested Nebraska field in 2018, estimated yield loss was 92% in the first 100 feet from the field edge, 31% at 200 feet and 20% at 400 feet. Missouri Extension reports losses of 17% to 31%. Infested plants that mature early can also lose yield to early pod shatter, and weakened stems can lodge.[1][3]
Health risk
The three extension sources describe it only as a pest of soybean; none of them mentions bites or any other harm to people.[1][2][3]
Control
Prevention
Late planting seems to be the best deterrent. Plant the fields at highest risk last, and rotate crops.[3]
Traps and physical control
Nebraska researchers have had some success reducing populations by hilling, that is, mounding soil around the plants.[3]
Pesticides
No tactic tested so far gives complete control. Seed treatments, foliar sprays and in-furrow insecticides may give some suppression, depending on how long adults keep emerging, the planting date and the weather. Minnesota Extension says seed-applied insecticides do not appear to work and has no management recommendations yet; the long, drawn-out emergence and repeated generations could make spraying adults difficult.[1][2]
When to call a professional
If you suspect soybean gall midge, contact your local extension agronomist. The Soybean Gall Midge Alert Network (soybeangallmidge.org) posts adult emergence reports and field alerts.[3][1]
Scouting soybean fields
Minnesota Extension says to begin scouting after plants reach the V2 stage; Nebraska Extension says to start at least 7 to 10 days after the first adult emergence is reported through the Soybean Gall Midge Alert Network. For early detection, check soybean fields that border last year's soybean fields, especially edges with dense vegetation, and check again after a hailstorm.[2][1][3]
Look for dark discoloration at the base of the stem, then peel back the stem skin in the darkened area to look for white or orange larvae. Orange larvae may not be present yet early in an infestation.[2][1][3]
Sweep nets are not a reliable way to detect adults. Corn rootworm emergence cages fitted with glass jars, set in last year's soybean fields, are the most effective way to monitor when adults come out.[1]
Common questions
- What are the little orange maggots at the base of my soybean stems?
- Bright orange larvae under the stem skin at the base of soybean plants are a telltale sign; Nebraska Extension calls the orange third-stage larvae the more characteristic feature of a soybean gall midge infestation. Younger larvae are white and can be confused with other insects.[1][2]
- Do seed treatments stop soybean gall midge?
- Not reliably. Minnesota Extension says seed-applied insecticides do not appear to be effective, Missouri Extension reports that Nebraska researchers found little data supporting them, and Nebraska Extension says no tactic tested has given complete control.[2][3][1]
- Why is the damage worst along field edges?
- Adults emerge from the soil of last year's soybean fields and move into nearby soybean, and the first larvae turn up in the plants closest to last year's field. Dense vegetation along the border is linked to more injury, possibly because it holds the water the adults need.[1][2]
Sources
- University of Nebraska-Lincoln Extension, “Soybean Gall Midge in Nebraska, NebGuide G2331 (J. McMechan, T. Hunt and R. Wright, April 2021).” extensionpubs.unl.edu/publication/g2331/html/view (accessed 2026-11-09)
- University of Minnesota Extension, “Soybean gall midge in Minnesota soybean (R. Koch and B. Potter).” extension.umn.edu/agriculture/crop-production/soybean/soybean-gall-midge-in-minnesota-soybean (accessed 2026-11-09)
- University of Missouri Extension, “Soybean gall midge spreading in Midwest (news release, April 17, 2024).” extension.missouri.edu/news/soybean-gall-midge-spreading-in-midwest (accessed 2026-11-09)
- iNaturalist, “Resseliella maxima taxon page (order and family).” www.inaturalist.org/taxa/907508 (accessed 2026-11-09)