Black cutworm is one of the most common cutworm species in the corn-growing area. Black cutworms generally migrate to Midwestern fields in the early growing season (late winter into spring) and inflict damage during the early vegetative stages of corn. Due to the sporadic nature of flights and favored host plants, field scouting is the most effective measure to determine if and when treatment may become necessary.
Identification and Scouting
What It Looks Like
Since black cutworms target corn early in the growing season, scouting right away is critical. Follow these tips to help you track threats:
- Scout once per week for three to four weeks after corn emergence, especially late-planted or weedy fields
- Check 50 plants at five locations in each field
- Dig around injured plants for live black cutworms
- Determine larval stage as the first to third instar are too small to cut plants
- Record the number of cut or damaged plants
- Record number and size of larvae per 100 plants and corn growth stage
- Recheck field 24 to 48 hours later
Impact on Crops
Depending on the size of your corn plant, a single black cutworm is capable of destroying up to four corn plants. And if your crops are planted late, rest in poorly drained areas or contained weeds prior to planting, your corn is at a higher risk.
Once a moth flight has been predicted and/or observed, farmers in the risk area should monitor growing degree day accumulations from the peak flight date, as moths will lay eggs on suitable hosts with larvae typically cutting corn plants beginning in the late third or fourth instar.
Management practices that can help reduce black cutworm include the following:
- Conduct tillage in the fall instead of the spring
- Avoid late planting
- Remove weedy vegetation through tillage or use of burndown herbicides.
- Consider making an insecticide application if greater than 3 percent of the plants are cut and larvae are still present.
Still have questions about protecting your yield against black cutworm? The experts at #TraitAnswers have the information you need to make your next insect management decision your best one yet.