Black Cutworm and Armyworm Counts on the Rise

Black cutworm moths

Last week, both Purdue University and the University of Kentucky reported high black cutworm catches. In addition, UKY caught a large number of armyworms in one of their traps.  Both of these moth species migrate into our area, lay eggs, and the developing larvae can be significant pests of corn and wheat.

Black cutworm—Females 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.  Unfortunately, there aren’t good “pre-control” options.  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 are showing damage, corn is in the V2-V6 stage, and larvae are less than 1 inch, treatment may be needed. We will provide updates over the next few weeks as planting begins (hopefully…) and if damage is reported.

Armyworm—Females 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. We will provide updates over the next few weeks.

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.

Author(s):