Farmers and crop scouts in Wisconsin are advised to increase monitoring for first-generation true armyworm larvae during the second half of June. This recommendation follows reports of heavy spring moth flights recorded by DATCP’s True Armyworm Network over recent weeks. As a result, caterpillars are now active in various crops across the state.
Recent observations found armyworm larvae in scattered wheat and corn fields. Wheat surveys in the east-central region detected low numbers—only one to two larvae per 100 sweeps—in about 14% of the 49 sites sampled. These counts remain well below the economic threshold of three larvae per square foot for small grains.
Armyworm larvae have also started to move into the edge rows of corn fields. Scouts should look for plants with ragged edges and frass, which indicate feeding damage. While it is normal to find a few edge-row plants with armyworm feeding, treatment is only recommended when specific thresholds are met. These include two or more armyworms (0.75 to 1.0 inch or smaller) per corn plant on 25% of plants, or one larva per corn plant on 75% of plants.
As of June 12, DATCP has not recorded any significant armyworm infestations. However, mid- to late June remains a critical period for scouting outer corn rows and lodged wheat fields. Early detection and monitoring can help farmers manage potential armyworm damage effectively.
