The soybean gall midge might have been a late arrival to the Midwest. But it’s a pest still worth keeping an eye on moving forward. 

The insects’ presence in the region only goes back to 2011, and damage to plants wasn’t reported until 2016. Widespread infestations began in 2018. Now, soybean gall midge has been identified in five states: Iowa, Nebraska, Missouri, Minnesota and South Dakota. 

Here’s what to look out for — and how to manage potential infestation. 

What is a gall midge? 

Gall midges are insects from the fly family. Adults have long legs, thin abdomens, mottled wings, are about a quarter-inch long and have hairy-looking antennae. Alternating black and white-colored stripes can be found on both their antennae and legs. 

However, adults are rarely spotted in the field and are not a danger to crops. Only the larvae feed on soybean plants and can be a risk to future yields.

How to identify soybean gall midge in the field

Researchers previously thought gall midge infestation only happened after a field had already been damaged from severe weather or another disease. However, in the last few years (starting in 2018), these infestations have happened independently. It’s important to be vigilant about checking fields, even if there hasn’t been other damage.

Scout soybean fields as the plants start to reach V3, around early June. Since gall midge overwinters under the soil, then pupates in spring, this window of time is usually when they’ll emerge from the soil and lay their eggs. After hatching, larvae will feed on the stems of soybean plants.

Infestation usually starts along the edges of a field. Signs of damage will include wilting or dying plants, brittle or swollen stems, or dark discoloration at the stem base.

If there are signs of damage from gall midge, pull back the outer layer of the soybean stem to check for larvae that look like maggots. They’ll likely be cream-colored or white during early stages, but will shift to bright orange as they age.

Even if gall midge aren’t found at the V3 stage, continue scouting throughout the growing season. Two generations usually reproduce per season, so they can pop up late.

Management strategies for gall midge

Early detection is especially critical for these critters. A solid scouting plan can help farmers stop damage before it starts. 

Since gall midge is still a relatively new threat, mitigation tactics are limited. Entomologists have begun to learn more about these pests and how to manage them. But until some of that research yields a complete control method, farmers will have to settle for limiting the bugs as much as possible. Foliar insecticides and seed treatments can help. 

Crop rotation can also be an effective tactic, since most gall midge damage happens in fields that were planted with soybeans the previous year.For any questions about soybean gall midge symptoms, control or identification, reach out to your local AgriGold agronomy expert for more information and support.