Soybean tentiform leafminer spreading

Researchers across the Upper Midwest are keeping a close eye on soybean tentiform leafminer, an insect that’s recently been confirmed in soybean fields across several states – including Minnesota, Iowa, Nebraska and the Dakotas. So far it has not been detected in Wisconsin.

Supported by the North Central Soybean Research Program, a multi-state survey effort that launched in summer 2025 brought together entomologists from across the region. They are working to determine where the insect is appearing in soybeans and how severe infestations may be.

“This past summer was the first year of a coordinated multi-state survey,” said Robert Koch, University of Minnesota-Extension entomologist. “Through that work, we detected soybean tentiform leafminer in soybean fields across much of the Upper Midwest.

“The soybean tentiform leafminer is a tiny moth whose larvae, or caterpillars, live inside and feed on soybean leaves. Through their feeding, the caterpillars are hollowing out, or mining, the leaf tissue and then those tissues die, reducing the plant’s ability for photosynthesis. A single caterpillar doesn’t destroy a large area within a plant, but over a season the damage will add up from numerous caterpillars and multiple generations of the moth.”

The pest has likely been present in the region for many years, but Koch said it historically fed on native plants in wooded areas. What’s new is its increasing presence in soybean fields.

“It’s probably always been here, but hanging out in wooded areas,” he said. “In some areas now, it’s feeding on soybean and that’s where our focus is.”

Survey results suggest infestations tend to be most noticeable along field edges, particularly near trees and wooded areas, rather than throughout entire fields.

“I don’t want to set off alarms,” Koch said. “Most of the fields we’ve looked at have fairly low infestation levels.”

But some fields have seen larger populations, making awareness and scouting important. Producers should look for leafminers on the undersides of soybean leaves while scouting for other pests and report suspected sightings to local Extension educators – especially in new areas.