JEFFERSON CITY, Mo. (DTN) -- The first soybean gall midge adults of 2025 have emerged at a trapping site in east-central Nebraska, signaling that soybean farmers should begin scouting for the pest, especially those who planted their beans in late April or early May and have had issues in previous seasons.

The Soybean Gall Midge Alert Network posted an alert on its website on May 30 stating that two adults had been collected in Saunders County, west of Omaha, Nebraska.

"We collected one male and one female from the trapping site at the university's research station today," said University of Nebraska entomologist Justin McMechan during a phone interview with DTN. "This is the same emergence date as last year, and we've been pretty consistent with emergence at the end of May the past three years."

Soybean gall midge is a tiny, slender fly that overwinters as larvae in the soil. In the spring, the insect pupates, and the adults emerge. The females lay their eggs in small cracks or fissures on soybean stems near the base of the plants. After the eggs hatch, the larvae feed on the tissues within the stem under the epidermis, disrupting nutrient and water movement. As they mature, the maggots turn from white to orange.

Once emergence begins, it typically continues for 25 to 35 days, though some overwintering sites have seen emergence last for 44 days. Once emergence occurs, white larvae are usually found in soybean stems within nine to 12 days.

Infested plants can quickly wilt and die or break off at the feeding site. Significant yield reductions may occur, especially at the field edge.

"Last year, some research on yield impacts here in eastern Nebraska showed anywhere from 12- to 34-bushel yield losses in the first 100 feet of the field," McMechan said. "Growers tell us they see losses from 18% to 31%."

The entomologist noted that while the V2 soybean growth stage is usually when fissures develop on soybean stems, there are varietal differences, so it's important to assess the plants before pulling the trigger on an insecticide application.

"If you got your beans in early, say the last few days of April or the first few days of May, you're probably looking at V2 beans, but before you do anything, you need to look for those fissures," McMechan said. "That's the critical part of deciding whether to spray or not. If you've had problems with gall midge before and you're finding fissures, your crop is susceptible."

Though orange larvae were first observed in Nebraska in 2011, no specimens were collected or stored. It wasn't until 2018 that soybean gall midge was determined to be a new species that had not been documented. Since then, the Soybean Gall Midge Alert Network has documented the pest in 178 counties in seven states, including 14 new counties in 2024.

"Based on 2023 USDA cropland data, the counties where gall midge has been found total 19.3 million acres," McMechan added. "It's been found in counties accounting for 90% of Nebraska's soybean acres."

MANAGEMENT TIPS

Management for soybean gall midge has been a hit-or-miss proposition. Chemical control has shown some results, but foliar-applied insecticides have been inconsistent between locations and years. McMechan previously told DTN that growers should only consider applying if they have a history of issues with soybean gall midge and observed the pest in an adjacent field the previous season.

He recommended using an insecticide that contains a pyrethroid. A foliar treatment prior to the V2 growth stage isn't necessary because the plants have not developed the fissures or cracks at the base of the stem that provide the entry point for egg laying. Because soybean gall midge is a field edge-infesting pest, growers may only need to treat the first 100 feet of a field.

Infestation can also be controlled by covering the base of the soybean plants with soil. This "hilling" has been found to be a very effective strategy with almost complete control of soybean gall midge. However, the practice is difficult to implement when soybean plants are small, as they can easily be completely covered by soil.

SCOUTING TIPS

The following are some soybean gall midge scouting tips:

-- Scout edges of soybean fields adjacent to fields that were planted to soybeans the previous year, especially if they had a gall midge infestation.

-- Focus on fields that are V2 or older -- that's when the soybean stem starts to crack along the surface near the soil line. The adult midge lays eggs in these fissures.

-- Look for dark brown or black discoloration of the base of the stem. Scrape the exterior layer of the stem away to reveal larvae that start white and turn orange as they mature.

You can set up an alert notification of gall midge discovery here: https://soybeangallmidge.org/….

Jason Jenkins can be reached at jason.jenkins@dtn.com

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