By Blake Jackson
The soybean tentiform leafminer (STL) moth is tiny no larger than George Washington’s nose on a quarter but its impact on soybeans can be significant.
“Ivair Valmorbida, University of Missouri Extension state field crops and forage entomologist, warns not to underestimate this pest,” said Valmorbida. STL was confirmed in 2025 in Cooper County, particularly in fields adjacent to wooded areas, its preferred habitat.
Macrosaccus morrisella, the scientific name for STL, historically fed on native legumes such as American hog peanut and slickseed fuzzybean. Recently, it has adapted to feed on soybean, Missouri’s leading crop. First recorded on U.S. soybeans in 2021, STL is most common in Minnesota but is spreading.
The moth features wings with orange, white, and gray-black markings. Females lay eggs on the underside of soybean leaves. Larvae create mines in the leaves, which remain confined between the midribs and lateral veins. These mines grow over time, forming white blotches as leaf tissue dies, reducing photosynthetic capacity.
Because STL is a new threat, research on management is ongoing. Early studies indicate insecticides with translaminar activity can decrease larval numbers and leaf damage. Screening soybean varieties has also identified cultivars showing reduced susceptibility.
Valmorbida recommends monitoring field edges near wooded areas for early infestation signs. Farmers should notify their local MU Extension agronomist if STL is suspected or contact Valmorbida directly at ivairvalmorbida@missouri.edu. Early detection is key to limiting this emerging pest’s impact on soybean production.
Photo Credit: istock-urpspoteko
Categories: Missouri, Crops, Soybeans