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Soybean gall midge threatens early-season planting

Think June before seeding soybeans to reduce the pest threat to plants.

Mindy Ward, Editor, Missouri Ruralist

May 1, 2024

3 Min Read
Close up of soybean gall midge
LENGTHY VISIT: White and orange soybean gall midge larvae feed on plants. Adults deposit eggs in fissures or cracks, which appear at V2 stage in soybeans. The larvae have multiple instars ranging from translucent to orange and can feed all season, damaging plants and reducing yield. Adam Sisson, Iowa State University, Bugwood.org

Soybean gall midge upped its appearance by 10 days in Nebraska crops, and that could mean trouble for Missouri soybean growers who plant early.

First found in Missouri in 2019, the pest is in the state’s far northwestern counties of Atchison and Holt, University of Missouri Extension state entomologist Ivair Valmorbida says. And soybean gall midge can cause heavy damage:

  • Yield loss from soybean gall midge ranges from 17% to 31%.

  • Plant death occurs at 21 days in high-pressure areas.

The relatively new pest, reported six years ago, continues to expand its reach, moving into northeast Kansas last year. Missouri farmers along the northern border counties of Iowa, Nebraska and Kansas should be on guard and prepare for this growing season.

Valmorbida, and Justin McMechan, Nebraska Extension crop protection and cropping systems specialist, recommend these crop management strategies:

  • Plant soybeans after June.

  • Plant high-risk fields last.

  • Rotate, rotate, rotate.

As soybean gall midge emerges in mid-June, it flies to a neighboring soybean field to lay eggs typically into cracks or fissures at the base of a plant in the V2 stage. Those eggs grow to larvae and feed off plants. Early-planted soybeans are at V2 about the same time as adult emergence.

Delayed planting moves the V2 stage beyond the emergence timeline, removing a soybean host plant for the pest. Adult soybean gall midge only survives for 15 days.

McMechan noted that seed treatments and foliar fungicides don’t necessarily work on soybean gall midge.

“They have some effect when you look at reductions in larval number and increasing rates,” he says, “but then when we get down to yield, we tend to lose those differences. We just don’t get consistent results.”

UNL researchers saw some success in reducing populations by hilling or mounding of soil around the plants. Hilling at the V2 stage had the lowest larvae per plant.

Greatest threat area on farm

If soybean gall midge is present, plant injury is likely along field edges near dense vegetation and waterways, and in fields directly adjacent to those planted in soybeans the previous year.

However, Valmorbida explains that larvae have also been found on alfalfa and sweet clover and may infect other legume crops.

He warns farmers to pay special attention to fields after a weather event.

“It is important to scout after a hailstorm, since hailstones create wounds on the stems,” Valmorbida says, “making openings for disease and pests to enter.”

Get out and scout

Valmorbida advises farmers to inspect fields after soybean plants reach the V2 growth stage and look for dark discoloration at the base of the stem.

“Peel back blackened tissue in discolored areas near the base of the soybean stem to look for white or orange larvae,” he adds. “Heavily infested plants will wilt and die.”

Life cycle of soybean gall midge

A graphic illustrating soybean gall midge movement

Consult your local Extension agronomist if you suspect soybean gall midge in your crops.

Sign up for free soybean gall alerts from the Soybean Gall Midge Alert Network or MU Extension’s free Integrated Pest Management Pest Monitoring Network.

About the Author(s)

Mindy Ward

Editor, Missouri Ruralist

Mindy resides on a small farm just outside of Holstein, Mo, about 80 miles southwest of St. Louis.

After graduating from the University of Missouri-Columbia with a bachelor’s degree in agricultural journalism, she worked briefly at a public relations firm in Kansas City. Her husband’s career led the couple north to Minnesota.

There, she reported on large-scale production of corn, soybeans, sugar beets, and dairy, as well as, biofuels for The Land. After 10 years, the couple returned to Missouri and she began covering agriculture in the Show-Me State.

“In all my 15 years of writing about agriculture, I have found some of the most progressive thinkers are farmers,” she says. “They are constantly searching for ways to do more with less, improve their land and leave their legacy to the next generation.”

Mindy and her husband, Stacy, together with their daughters, Elisa and Cassidy, operate Showtime Farms in southern Warren County. The family spends a great deal of time caring for and showing Dorset, Oxford and crossbred sheep.

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