Pictured: Black cutworm trap. Photo by K. Hamilton DATCP
Development of black cutworm larvae has slowed with the cold weather, but growth and feeding will resume once seasonable temperatures return. The opening of the peak seedling corn damage window in Wisconsin is expected during the last two weeks of May.
Regional cutting dates are determined by calculating 300 gdds from the first intense moth captures in traps (also referred to as the “biofix”), which reflect the heat units required for black cutworm to reach the damaging fourth-instar larval stage. This spring, the earliest intense captures were recorded on April 14. Trap locations have accumulated approximately 100-175 degree days over the last three weeks, and the warmest southwestern sites will surpass the 300-degree-day-threshold by May 19. Other southern and central Wisconsin locations will accrue degree days more gradually and the peak corn cutting widow is forecast to open between May 21 and 27.
The Black Cutworm Trap Network has now completed week six of the 11-week trapping survey (March 25 to June 11). During the monitoring period ending May 6, the network’s 99 traps collected 542 moths, a steep decline from 1,336 moths the previous week. The cumulative count of 2,637 moths is similar to the 2,096 moths captured by this time in 2025.
Learn more: https://datcp.wi.gov/Pages/Programs_Services/TrapNetworks.aspx
