Second finding of new soybean pest confirmed in Missouri

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

Valmorbida said Missouri’s second confirmed case was in Macon County on Aug. 19. The first case of this pest in the state was in a Cooper County soybean field in August 2025.

Soybean tentiform leafminer (Macrosaccus morrisella) was detected feeding on soybean in Minnesota in 2021 and has since been detected in South Dakota, North Dakota, Iowa and Nebraska.

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

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.

On the underside of the leaves, mines enlarge to become elongated, oval white blotches. On the upper side of the leaves, these mines become tentiform – slightly raised, or tented.

Soybean tentiform leafminer appears primarily along field edges near forested areas.

Valmorbida says this oligophagous microlepidopteran is native to North America and was historically restricted to two legume species, American hogpeanut and slick fuzzybean, both of the Fabaceae family, the same family as soybean.

There are no well-established management practices for this insect, but University of Minnesota researchers report that several parasitic wasps, natural enemies of the soybean tentiform leafminer, and translaminar insecticides could provide control. Its potential damage is yet unknown, says Valmorbida.

Valmorbida is working with other universities to determine the distribution of the soybean tentiform leafminer in soybean fields. He recently authored the MU Extension publication Soybean Tent Leafminer in Missouri Soybean, which is available for free download.

You can follow updates on tentiform leafminer and other pests at CropWatch, a resource provided by University of Nebraska–Lincoln.

Photo

Soybean tentiform leafminer. MU Extension crops entomologist Ivair Valmorbida says farmers should scout soybean fields for the soybean tentiform leafminer, a new pest found for the first time in Missouri in August. Photo by Ivair Valmorbida.