Krista Hamilton, DATCP
Black cutworm moths arrived in substantial numbers this week. The DATCP network of 50 pheromone traps collected 567 moths during the reporting period ending May 4 (average of 11.3 per trap). Significant captures were documented at 15 of the 50 sites, with the highest counts recorded in Barron, Chippewa, Dunn, and Rusk counties. A significant capture of nine or more moths in two nights indicates a large flight has occurred and that a corresponding increase in cutworm egg laying can be expected. The first major flight also marks the point to begin counting degree days to forecast the peak seedling corn damage window. From the date of a significant capture, an average of 300 degree days (modified base 50°F) is required for the black cutworm to develop from the egg stage to the damaging fourth-instar larval stage.
The black cutworm migrates northward each spring from overwintering areas near the Gulf of Mexico and Texas. When appropriate weather systems occur, the moths can reach Wisconsin from Texas in only two days. The first moths were recorded in traps on April 8 this spring and the cumulative count as of May 4 is 733 moths. This total is more than two times higher than the 216 moths captured by the same time last year. The latest counts for the state’s 50 trap sites are available each Thursday on the DATCP Black Cutworm page.