First Nebraska report of soybean leafminer

By Scout Nelson

As soybean fields in Nebraska dry down and approach harvest, a new concern has emerged with the confirmation of the first case of soybean tentiform leafminer (STL) (Macrosaccus morrisella) in the state on September 27, 2024.

This pest, a native leaf miner, was previously associated with two native plants: American hog peanut and slickseed fuzzybean. In recent years, however, STL has been observed infesting soybean crops.

The first reports of STL infesting U.S. soybean fields came from two counties near the Twin Cities Metro Area in Minnesota in 2021. By 2022, ten additional counties in Minnesota and three counties in South Dakota reported infested fields.

In 2023, North Dakota joined the list, with five counties reporting infestations. Now, Nebraska has become the only state to report an infestation this year, with a single infested field found in Madison County.

The adult soybean tentiform leafminer is a very small moth, measuring about 1/8 inch in length. Its wings are characterized by orange, white, and gray-black markings. The moth lays its eggs on the underside of soybean leaves.

Once the larvae hatch, they burrow into the leaf tissue, where they begin feeding. This feeding initially creates a serpentine-like mine in the leaf, which later expands into patches or blotches.

Multiple mines can occur on the same leaflet, but they do not cross the midrib or major leaf veins. The larvae, which are pale green to white, may occupy the same mine and will spin a silk retreat inside the mine to pupate.

Currently, there are no known management methods for controlling this pest. With harvest rapidly approaching, there is little immediate concern for Nebraska farmers.

However, the next step involves conducting growing season surveys of soybean fields to determine the prevalence of STL across Nebraska. Monitoring efforts will help ensure that any potential impacts on soybean production are addressed promptly.

Photo Credit:gettyimages-gilaxia