By Blake Jackson
University of Missouri Extension state crops entomologist Ivair Valmorbida has confirmed the discovery of a new soybean pest in Missouri.
The soybean tentiform leafminer was identified in central Missouri soybean fields during the first week of August, with MU Extension agronomist Todd Lorenz present when the pest was found.
While the insect has only been detected in one of more than 70 fields examined so far, Valmorbida notes its presence is cause for concern.
The soybean tentiform leafminer (Macrosaccus morrisella) was first reported feeding on soybeans in Minnesota and the Dakotas in 2021 and later in Nebraska in 2024.
According to the University of Minnesota, the pest also feeds on native plants such as American hogpeanut and slick fuzzybean, both members of the Fabaceae family, which also includes soybean.
This pest begins as a small white larva, turning pale green as it develops. Adult moths are tiny less than ¼ inch long with orange and white wings marked with gray-black patterns.
Females lay eggs on the undersides of soybean leaves, and the larvae feed within the leaf tissue, creating mines that do not cross the leaf’s main veins. Over time, the affected tissue dies, reducing the leaf’s surface area, much like defoliation.
Initially, the mines appear as small, narrow lines that expand into elongated, oval white blotches. These eventually become “tentiform,” meaning slightly raised, on the upper side of the leaves. Infestations typically occur along field edges or near wooded areas.
Currently, there are no established management strategies for this pest. However, research from the University of Minnesota suggests that natural predators such as parasitic wasps and the use of translaminar insecticides may help control infestations.
Valmorbida urges farmers to monitor their soybean fields closely and to contact their local MU Extension agronomist or reach him directly at 573-882-6446 or ivairvalmorbida@missouri.edu if they suspect the presence of the leafminer.
Photo Credit: istock-urpspoteko
Categories: Missouri, Crops, Soybeans