Management of Soybean Gall Midge in Iowa Scott Nelson ISA Research Agronomist
S
oybean gall midge is a relatively new species of soybean pest spreading in Iowa. Reports of potential soybean gall midge injury in the far western parts of Iowa were noted as early as 2016, with Iowa State University confirming soybean gall midge spreading as far east as I-35 with new confirmations in Marion County in 2023. Kansas, Missouri, Minnesota, Nebraska and South Dakota also face severe pest outbreaks.
A field perspective Through his normal scouting routine, Dennis Reinke, sales agronomist for NEW Cooperative, Inc., found soybean gall midge had invaded soybean fields in his territory. While Reinke and other producers in the western part of the state have dealt with soybean gall midge in the past, this is the most widespread they have seen the pest. Typically found in the field’s border near grassy areas, this year they located the soybean gall midge 150 feet from the border and in otherwise healthy plants. “That was alarming to me,” says Reinke. “The fact that the pest was found in fields with no symptoms of yellowing or wilting leaves or dead plants, and we were still finding it.” This is the largest outbreak he has found in his area near Moville west to the Missouri river.
The soybean gall midge life cycle Understanding the life cycle of soybean gall midge is crucial to managing this pest.
First-generation soybean gall midge emerges from the overwintering in grass waterways, fencerows and infested fields beginning in June and are weak flyers with a life cycle of three to five days. The adults cannot penetrate soybean stems and lay eggs into cracks and wounds in the soybean plant. These eggs hatch into larvae, and the larvae feed on stem and root tissue, leading to plant death. After feeding, the larvae pupate, fall into the soil and emerge as second-generation adults that spread further into the field. Most commonly, Iowa has two to three generations per year.
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