Only recently discovered, in 2017, soybean gall midge is a significant and fast-spreading new pest to Midwest growers. Significant yield reductions may occur, especially at the field edge where this pest first infests.¹ And to add to the challenge, soybean gall midge can be hard to identify, especially in the early stages of infestation.
But you don’t have to lose sleep over the difficulty of detecting soybean gall midge — we’ve saved you the headache and created a simple guide to help you scout for and manage this new pest.
Soybean gall midge identification
Soybean gall midge larvae typically infest soybean plants at the V2 growth stage or later, when cracks begin to develop in soybean stems, providing an entry point for females to lay eggs. Adult soybean gall midges are small flies, and females continuously emerge and lay eggs that hatch inside soybean stems during vegetative growth stages through pod fill.²
The pest then overwinters as mature larvae or pre-pupae in fields that were planted with soybean the previous growing season, with adults emerging from the soil in early June to repeat the life cycle.
How to identify soybean gall midge larvae
The larval form is typically the first you’ll see of this pest (eggs are not typically seen in the field and have not been described). The larvae are typically 0.2–2 mm and look like typical small maggots and do not have any significantly distinct features, making them hard to identify. Soybean gall midge larvae are legless and go through three instars (developmental phases). The first instar soybean gall midge is clear and small, second instars are milky-white or light orange, and third instars are larger and bright orange at maturity.
How to identify soybean gall midge adult flies
When scouting for soybean gall midge, it is unlikely that you will see adults in the field. If you do, you’ll find an insect resembling a slim-bodied fly with an orange abdomen and mottled wings. Adults are only 0.25" long, with long legs featuring alternating light and dark bands.
When scouting for soybean gall midge, be cautious of making a mistaken identification. Some cases reported as soybean gall midge have later been identified as white mold gall midge, a pest that feeds on the mold located in internal portions of stems and pods due to White mold infections. This pest, however, does not attack healthy soybean plants like soybean gall midge does.³
Signs of soybean gall midge infestation
Since soybean gall midge larvae feed inside the soybean plant, infestations can be hard to detect. Often, the first sign of infestation will be soybean lodging and death. Symptoms are typically most visible along field edges, while plants in the center of the field still look healthy.
Upon closer look, first symptoms of soybean gall midge on the plant show up as dark, discolored lesions on stems near the soil line (similar to the effects of fungal pathogens like Phytophthora and Rhizoctonia). You may notice the appearance of a namesake gall (a swelling, discoloration, or outgrowth of the stem), but galls are not always present.
Scouting for soybean gall midge
- Begin scouting first rows and field edges at V2 growth stage
- Look for dark lesions around base of stem, brittle stems, and/or breakage near the base of the plant
- Scout after hail storms or any weather event that could create wounds in the plant that allow for infestation
- Peel back the epidermis of the stem and look for small orange or white larvae in the stem interior
- If your crop is heavily infested, you will see wilted and dead plants
Soybean gall midge control recommendations
Soybean gall midge larvae are well protected inside the soybean stem, so unfortunately, there are no effective management practices recommended for soybean gall midge at this time, with seed and foliar insecticides proving ineffective in preliminary research. However, some studies suggest that a combination product containing a pyrethroid may be effective.⁴
For updates on how to control this emerging pest, follow the Soybean Gall Midge Alert Network for more information.
Experts are available to help you learn how more about soybean gall midge. Reach out to your seed retailer, a nearby extension office agent, or a seed company professional like your regional BASF representative.
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Endnotes
- Dean, Ashley, and Erin Hodgson. “Soybean Gall Midge.” Integrated Crop Management, crops.extension.iastate.edu/encyclopedia/soybean-gall-midge. Accessed 30 Oct. 2024.
- Temple, Laura. “Getting to Know – and Manage – Soybean Gall Midge - Research Highlight.” Soybean Research & Information Network, 21 Aug. 2023, soybeanresearchinfo.com/research-highlight/getting-to-know-and-manage-soybean-gall-midge/. Accessed 30 Oct. 2024.
- Dean and Hodgson. “Soybean Gall Midge.”
- “Notifications — Soybean Gall Midge Alert Network.” Soybean Gall Midge Alert Network, soybeangallmidge.org/notifications. Accessed 30 Oct. 2024.
