Scouting for black cutworm & armyworm


It’s that time of year to be scouting for the black cutworm and armyworm. Usually, we don’t see a lot of pressure from these pests as they do not overwinter in Ohio, but this year we are seeing high populations of the black cutworm and armyworm moths in surrounding states within the last couple of weeks. These species migrate into Ohio as moths and lay eggs which develop into larvae, and if not checked can cause measurable damage in corn and wheat.

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

– Black cutworm—Female moths like to lay eggs in fields with heavy weed cover; weeds like chickweed are especially favored by black cutworm. As these weeds are killed by tillage or herbicide, the larvae move to emerging corn. Although there are some hotspots for egg laying, these predictions are far from exact. Insecticidal seed treatments do not offer much protection, and tank-mixing an insecticide with early burn-down has limited efficacy if scouting has not been done to see if larvae are present. Instead, we recommend rescue treatments which are very effective in controlling damage. If more than 3% of corn plants are showing damage, and corn is in the V2-V6 stage, and larvae are less than one inch, treatment may be needed.

– Armyworm—Female moths like to eggs in grasses, especially wheat, where egg hatch occurs over a couple of weeks. As the larvae develop, they can defoliate wheat plants, leading to yield loss. If corn is planted into wheat fields or other grassy cover, then, like black cutworms, armyworms can also move onto corn. Again, like black cutworm, the best way to control armyworm is scouting and rescue treatments. We rarely see economic damage from armyworm, except in outbreak years and it is too early to know if this year is an outbreak.

Keep in mind that black cutworms can also cut the plant off below the soil surface, this 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 useful in minimizing infestations.

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

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