COLUMBIA, Mo. – University of Missouri Extension state crops entomologist Ivair Valmorbida has confirmed the presence of a new soybean pest in Missouri.

Valmorbida confirmed soybean tentiform leafminer in central Missouri soybean fields in the first week of August. MU Extension agronomist Todd Lorenz was present in the field when the pest was found. MU Extension specialists found in the insect in only one of more than 70 fields sampled so far, but its presence is concerning, says Valmorbida.

Soybean tentiform leafminer (Macrosaccus morrisella) was detected feeding on soybean in Minnesota and the Dakotas in 2021 and Nebraska in 2024.

According to the University of Minnesota, it feeds on two native plants, American hogpeanut and slick fuzzybean, both of the Fabaceae family, the same family as soybean, says Valmorbida.

This pest is a small white larva that turns pale green as it matures. The adult moths are less than ¼ inch long and have orange and white wings with gray-black marks.

Adults lay eggs on the underside of soybean leaves. Larvae feed inside the leaves and tunnel to create mines that do not cross the midribs or main lateral veins of the leaves. The mined tissue eventually dies, resulting in less leaf area, similar to defoliation.

On the underside of the leaves, mines enlarge from small, linear ones to become larger, elongated, oval white blotches. These mines become tentiform – slightly raised, or tented – on the upper side of the leaves. Soybean tentiform leafminer appears primarily along field edges and in forested areas.

There are no well-established management practices for this insect, but University of Minnesota researchers report that several parasitic wasps, natural enemies of the leafminer, and translaminar insecticides could provide control.

Valmorbida encourages farmers to scout soybean fields and to contact their local MU Extension agronomist if they suspect the presence of tentiform leafminer. Farmers may also reach Valmorbida at 573-882-6446 or ivairvalmorbida@missouri.edu.

Valmorbida is working with other universities to determine the distribution of tentiform leafminer in soybean fields. For more information, see the University of Minnesota publication “Soybean Tentiform Leafminer in Minnesota Soybean.” You can also follow updates on tentiform leafminer and other pests at CropWatch, a resource provided by University of Nebraska–Lincoln.

Photo

Soybean tentiform leafminer
University of Missouri Extension crops entomologist Ivair Valmorbida urges farmers to scout soybean fields for the presence of the soybean tentiform leafminer, a new pest found for the first time in Missouri in August. This microscopic image shows the larva, which turns into a moth that is only ¼-inch long. Photo by Ivair Valmorbida.