Identifying Corn and Bean Cutworms

By Andi Anderson

Reports of caterpillars feeding at the tips of corn ears have increased, causing confusion among farmers trying to identify the pest. The two most common culprits are the corn earworm and the western bean cutworm.

Although their feeding locations are similar, they are different pests, and knowing the distinction is important for crop monitoring and management.

The western bean cutworm is a native pest of corn and dry beans. It has only one generation per year and overwinters in the soil. Moths emerge in late spring or early summer and lay eggs on host crops.

Young larvae are purple with black heads, later turning tan with stripes and orange heads. Mature larvae are smooth, granular, tan or gray in color, and can be recognized by two dark rectangles behind the head. Several larvae can infest a single ear, feeding on tassel tissues, silks, cob tissue, and developing kernels.

In contrast, corn earworm does not overwinter in northern states but migrates from the south each summer. It can have multiple generations, with moths laying eggs on fresh corn silks.

The larvae have an orange head, alternating light and dark stripes, and are covered with small hairs and bumps called tubercles.

They can vary widely in color, from green to black. Unlike western bean cutworm, corn earworm larvae are cannibalistic, meaning usually only one larva is found in an ear. They feed mainly on silks and kernels at the ear tip, although they sometimes feed deeper inside.

Identifying which pest is present is important because both can cause feeding injury that increases the risk of ear molds. Farmers who are unsure can contact local extension agronomists for help in identification.

Accurate pest identification ensures better decisions for managing fields, reducing crop loss, and safeguarding corn quality.

Photo Credit: getty-images-elhenyo