Cutworm reduced overall yield in the U.S. and Ontario by over 95 million bushels in 2025, a degree of damage second only to that caused by corn rootworm.¹
"Cutworm" is a generic term for multiple species of larval moths. Adult moths typically do not damage plants, with the exception of Western bean cutworm, which feeds on and damages corn ears. Understanding cutworm lifecycle and how to identify different cutworm can help you limit impact on yield.
Cutworm life cycle and influencing factors
Timing and length of each lifecycle stage vary across species.
For example, black cutworms lay eggs in early spring, dingy cutworms in late summer or fall. Incubation periods vary by species and climate, ranging from two to 14 days. Some species lay a single egg while others lay rows of more than 600. Some cutworms can produce three or four generations per season while others may produce only one.
Cutworm populations are affected by rain and wind during migration. In warmer regions, cutworms may overwinter in the soil under crop residue as larvae and pupae, but in colder regions, they migrate north to south each year. These moths rely on the spring southern winds to migrate north. If wind or rain impede migration, infestations are typically lower. After northern migration, most cutworms go through a few life cycles, with the first generation causing the most damage.²
Tracking migrations with cutworm traps can help gauge the upcoming season's infestation, and differentiating cutworm damage from other insect pests is key.
Ideal habitat for cutworms
Cutworms are most prevalent in fields with:
Heavy plant cover or crop residue
Cover crops or unsprayed crops
Low, damp soil with poor drainage
Substantial fall and early season weed growth
What do cutworms look like?
Scout for cutworms every 7-10 days until corn reaches the V5 growth stage. Larvae hide in plant debris or just under the soil surface during the day, typically feeding at night, making damaged or cut plants easier to spot than the cutworm larva itself. If you spot one, it should:
Be approximately 2" long at maturity
Be smooth, not hairy (and they can appear either glossy or dull)
Curl into a C-shape when disturbed
Appear in a range of colors: brown, tan, pink, green, gray and black. They can be solid colors or striped and spotted.
Types of cutworms
The most significant cutworm species include:
Black cutworm is one of the major culprits of yield damage. Though the Dingy cutworm moth isn't the primary problem, if you spot the moth, that means damaging larva are also present. Claybacked cutworm larvae can be identified by their distinctive stripe.
Black cutworm: Larvae can be light gray, gray-brown to nearly black. Skin appears greasy with bumps visible under magnification. No distinct stripe along the back and a brownish head with dark spots. Damage includes cutting seedlings, feeding on stems below the soil surface by more mature larvae, and leaf feeding on emerged corn.
Dingy cutworm: Dull, dingy larvae with mottled coloring and a thick gray stripe along the back. Light gray V‑shaped patterns on each segment. Dingy cutworm climbs to feed on leaves at or above soil, causing defoliation, stunting and potential plant death.
Claybacked cutworm: Clayback cutworm larvae are a translucent, pale gray with a gray-brown head and bars on the face. A distinctive broad yellow-brown stripe runs down the back. They damage corn by leaf feeding and plant cutting.
Western bean cutworms: Despite the name, Western bean cutworm has expanded eastward from the Great Plains. Dark-brown larvae with faint diamond-shaped markings on the back. Color lightens to pinkish brown as they mature. Larvae feed on pollen in the developing tassel within the flag leaf. After tasseling, the larvae feed on silk in the ear.
