They are smooth caterpillars that range in color from grey to dark brown to almost black. Cutworms usually damage corn by cutting off small plants at ground level or by tunneling into the stalk, similar to the potato stem borer. Occasionally, they may feed on the leaves of small plants similar to armyworms. Cutworm larva Cutworm infestations are infrequent and unpredictable. Preventative treatments applied at planting times are not recommended.
Reliable chemicals are available for controlling outbreaks after cutworms appear.
Control is recommended if more than 5 percent of the plants show damage and the cutworms are still under 2.5 cm in length. Two species of rootworms damage corn in Ontario. The adult of the northern corn rootworm is a light green to greenish-yellow beetle about 5 mm in length. The Western corn rootworm is a slightly larger beetle that is yellow with black stripes . Western corn rootworm adult Corn rootworms spend the fall, winter and spring as eggs in the soil.