Black cutworm is likely to start appearing soon if they haven’t already. Some fields where corn has emerged may already be experiencing black cutworm damage. Their movement is sporadic, but they typically affect corn, wheat, tobacco and vegetable fields. Growers need to be diligent about scouting for black cutworm this growing season to avoid yield loss. Here are a few tips to keep in mind when scouting for and managing black cutworm.
Black cutworm arrives in growers’ fields as moths, where they lay eggs that hatch as larvae. The larvae damage corn crops as they begin chewing the early-stage plants around V2 or V3. Black cutworm larvae are grey to black in color with dark bumps alongside their body. Iowa State University Extension and Outreach describes them as having “grainy, light grey to black skin and four pairs of fleshy prolegs on the end of the abdomen.” They are often times confused with armyworms or other types of cutworms, so getting an official confirmation of the pest may be important to ensure you’re implementing the best management practices.
Scouting typically begins in April and May in the form of monitoring flight paths of black cutworm moths through pheromone traps, which is discussed in more detail below. After black cutworm has transformed to larvae, growers need to look for a few things as they scout fields during the early stages of corn development. Experts recommend scouting for damage every week up until the V5 stage. This process includes checking several areas of your field, not just one. Start with the fields that were planted first. Look in the weeds and grassy areas, or if you have a cover crop, moths could lay their eggs there as well. Walk the rows and look for some of the key symptoms, including very irregular cut leaves, necrosis on both ends of the plant, wilting and leaf discoloration. If you detect areas with these symptoms, you can dig around the plants to carefully extract the larvae to confirm their presence. Economic thresholds vary dependent on your environment, but two to five black cutworms per linear row should be detected before treatment is considered. Check with your local extension office to get the appropriate threshold for your region.
As black cutworm moths begin their migration, pheromone traps can be set to capture the moths. Experts can then estimate potential infestation levels in the area and help predict their cutting dates by incorporating growing degree days. This step essentially helps experts forecast the presence of black cutworms in your area and when they are predicted to emerge as larvae and begin feeding on plants. Your local extension offices should have a list of anticipated cutting dates, so consult with their experts if you suspect black cutworm infestation. It’s also important to know that pheromone traps alone should not be the only management practice implemented to help ward off the pest.
Stine Agrisure® Viptera® brand corn can offer some suppression of black cutworm. The Agrisure Viptera 3110 trait stack provides season-long control from black cutworm and other insects such as the European corn borer, southwestern corn borer, southern cornstalk borer, corn earworm, fall armyworm, dingy cutworm, beet armyworm, western bean cutworm, sugarcane borer and common stalk borer. These are represented as -20 or -20/LibertyLink® hybrids.
Stine® Agrisure Duracade® brand corn is another product that can help combat black cutworm. For example, Stine Agrisure Duracade 5222 E-Z Refuge® blend brand corn is an all-in-one system for corn pest management. The product boasts two modes of action to help tackle yield-robbing lepidopteran corn pests such as black cutworm. We recommended Stine Agrisure Duracade hybrids R9540-32 Blend, R9529-32 Blend, R9653-32 Blend, R9734E-32 Blend, R9744-32 Blend, R9734-32 Blend and R9739E-32.
Although helpful in mitigating black cutworm, Viptera and Duracade treated corn must be ingested by the cutworm for it to die off, so it’s more of a reactive treatment to suppress black cutworm. Consult the 2019 Syngenta Stewardship Guide for rules and regulations before purchasing Stine Agrisure products.
If you don’t have Bt traits planted and you’ve hit your economic threshold for black cutworm, then it’s time to spray. According to the University of Minnesota Extension, post-emerge insecticides work well against black cutworm infestations. Experts recommend T-band applications for granular insecticides. As always, read and follow labels and use rates before applying an insecticide.
For more information about scouting for black cutworm and best management practices, contact your local Stine agronomist or university extension office.