By Scout Nelson
Army cutworm moths are being seen in large numbers across South Dakota, with reports of mass populations already confirmed in the Black Hills region. These migratory insects are expected to move eastward as the season continues.
Farmers are concerned because the moths lay eggs in newly planted winter wheat fields. The eggs hatch quickly, and the caterpillars feed on seedlings until the first hard frost.
The moths are identified by their tan and brown wings, marked with a light-colored dot above a boomerang shape. Young caterpillars are small and greenish-brown, while older ones turn dull gray with pale stripes running along their bodies. All caterpillars have a light brown head.
The life cycle of the army cutworm includes migration between the Great Plains and the Rocky Mountains.
They spend summers in the mountains feeding on nectar, then return to the plains between August and October to lay eggs in cultivated fields and winter wheat. Caterpillars feed through fall and again in spring before pupating in the soil.
Experts suggest that frequent rainfall and favourable conditions this summer contributed to high survival rates. As a result, more moths are now returning east into South Dakota.
Caterpillars feed mainly at night, clipping plants near the soil surface and causing patches of damaged wheat.
They do not destroy the plant crown, so regrowth can occur. However, heavy infestations can spread quickly across fields.
Farmers are advised to scout regularly by checking soil for hidden caterpillars. Management is recommended if two to four caterpillars per square foot are found, or if large patches of defoliation are visible. Insecticide treatment is suggested when numbers are high.
Photo Credit: istock-ligora
Categories: South Dakota, Crops, Wheat