Now is a good time to scout for Western bean cutworm eggs and larvae, based on degree-day accumulations across the Corn Belt.
Corn crops in the late whorl stage are most attractive to egg-laying females. The eggs are white and dome-shaped when first laid but turn purple just prior to hatching.
Eileen Cullen, University of Wisconsin extension entomologist, recommends that farmers apply a foliar insecticide treatment no later than when 8% of 100 corn plants contain egg masses and/or small larvae.
Young western bean cutworm larvae feed initially on pollen but will move quickly to leaf tissue, silks, ears and corn kernels, according to Erin Hodgson, Iowa State University extension entomologist.
“One larva per plant usually does not cause severe damage to the ear,” she writes in the Integrated Pest Management News. “But several larvae feeding on one ear could substantially reduce yield because western bean cutworms are not cannibalistic, compared with corn earworms.”
Hodgson recommends using an insecticide when 90 percent of tassels have emerged. If the tassels have already emerged, she recommends timing applications for when 70 to 90 percent of the eggs have hatched. She adds, “Once the larvae reach the ear tip, control is nearly impossible.”
In the following video, Missy Bauer, Farm Journal Associate Field Agronomist, gives you a first-hand look at newly hatched larvae and some additional thoughts on your control options.