We do not recommend planting-time insecticide treatments for black cutworm control but instead encourage farmers to scout fields for larvae cutting corn. Larvae are large enough to begin cutting when about 300 base-50 degree days have accumulated since eggs were laid. The map shows the anticipated date when cutting is likely to begin, based on accumulated base-50 degree days as of May 3, and assuming average temperatures over the next 2 weeks. This year's map is simple compared with previous years' maps, largely because of the uniformity of flight arrival in Iowa. Leaf-feeding by cutworms usually appears before cutting occurs.
Black cutworm has four tubercles of unequal diameter on the top of each body segment.
Begin scouting a day or two before the projected scouting date for your area. Fields with early spring weed growth, especially where tillage was delayed until just prior to planting, and corn planted into soybean stubble are the most likely areas for black cutworm problems. Look for leaf feeding as a sign of early cutworm injury. If you find leaf feeding, try to find the larva responsible in the soil near the damaged plant. Dingy cutworms look much like black cutworms but rarely if ever cause economic damage and do not warrant treatment.