Missouri soybean growers are being urged to watch their fields following the state’s second confirmed discovery of the soybean tentiform leafminer.
University of Missouri Extension crops entomologist Ivair Valmorbida confirmed the pest in Macon County on Aug. 19. Missouri’s first known case was discovered in a Cooper County soybean field in August 2025.
The soybean tentiform leafminer was first detected feeding on soybeans in Minnesota in 2021. It has since been reported in South Dakota, North Dakota, Iowa and Nebraska.
The pest begins as a small white larva before turning pale green as it matures. Adult moths measure less than one-quarter inch long and have orange and white wings marked with gray and black.
Adult moths deposit eggs on the underside of soybean leaves. After hatching, the larvae tunnel through the leaf tissue, creating mines that stop at the leaf’s main veins. Damaged areas eventually die, reducing the amount of healthy leaf tissue available to the plant.
The mines appear as elongated white blotches on the underside of leaves. On the upper surface, the damaged areas become slightly raised or tent-shaped.
Infestations have primarily been found along soybean field edges near wooded areas. Growers should pay particular attention to those locations while scouting.
Researchers have not yet determined how much yield damage the pest could cause, and no standard management recommendations have been established. Research from the University of Minnesota suggests parasitic wasps and certain insecticides capable of penetrating leaf tissue may offer some control.
The insect is native to North America but historically fed on American hogpeanut and slick fuzzybean. Both plants belong to the same family as soybeans.
Valmorbida is working with researchers from other universities to determine how widely the pest has spread. Farmers who suspect soybean tentiform leafminer activity should contact their local MU Extension agronomist. Valmorbida can also be reached at 573-882-6446 or ivairvalmorbida@missouri.edu.
Additional identification and scouting information is available through MU Extension’s free publication, “Soybean Tent Leafminer in Missouri Soybean,” at extension.missouri.edu/publications/g4444.
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