Screening for black cutworm and armyworm

It’s that time of year to look for black cutworm and armyworm. Usually we don’t see a lot of pressure from these pests because they don’t overwinter in Ohio, but this year we are seeing heavy populations of black cutworms and armyworms in surrounding states over the of the last two weeks. These species migrate into Ohio as moths and lay eggs which larvae and, if left unchecked, can cause measurable damage to corn and wheat.

Andy Michel, crop agronomist entomologist at OUS Extension, provides the following summary regarding each of these pests:

– Black cutworm—Female butterflies like to lay their eggs in heavily weedy fields; weeds such as chickweed are particularly favored by black cutworm. As these weeds are killed by tillage or herbicides, the larvae move to the emerging corn. Although there are spawning hotspots, these predictions are far from accurate. Insecticide seed treatments do not offer much protection, and tank mixing an insecticide with an early burn has limited effectiveness if scouting has not been done to see if larvae are present. Instead, we recommend rescue treatments which are very effective in controlling the damage. If more than 3% of the corn plants show damage and the corn is at the V2-V6 stage and the larvae are less than one inch, treatment may be required.

– Armyworm—Female moths love eggs in grasses, especially wheat, where egg hatch occurs within weeks. As the larvae develop, they can defoliate wheat plants, causing yield loss. If maize is planted in wheat fields or other grassy cover, then, like black cutworms, army worms can also move onto maize. Again, like the black cutworm, the best way to control the armyworm is through scouting and rescue treatments. We rarely see economic damage from the army worm except in epidemic years and it is too early to know if it is an epidemic this year.

Keep in mind that black cutworms can also cut the plant below the soil surface, it would look like a wilted corn plant. Corn hybrids with the Herculex I transgenic trait can control black cutworm larvae. Black cutworms have a strong relationship with weed infestations, so weed control can be very helpful in minimizing infestations.

Brooks Warner is the Extension Educator for OSU Extension Clinton County.