Plant Problem Diagnostic
Cutworms: How to Identify and Stop Them
The short answer
Cutworms are dull brown, smooth caterpillars, 1 to 2 inches long, that curl into a C-shape when disturbed. They hide in the soil by day and feed at night, cutting young seedlings and transplants off at or just below the soil line. The most effective least-toxic control is a physical barrier: place a collar (cardboard, a paper cup, or a can with both ends open) around each transplant, sunk 1 to 2 inches into the soil and standing at least 3 inches above it.
Coarse materials like crushed oyster shell or diatomaceous earth around stems also deter them, and tilling the soil in spring or fall exposes overwintering larvae to predators and cold. If damage continues after collars are in place, or you are not certain cutworms are responsible, dig gently around a damaged plant at night or check with your local Extension office before escalating.
How to identify cutworm damage
The signature sign is seedlings or transplants cleanly cut off at the soil line and toppled, often overnight. Damage is worst early in the season when stems are small and tender.
- Smooth brown or gray caterpillars that curl into a C when touched
- Found on or just below the soil surface near damaged plants
- Active at night; plants look fine at dusk and are cut by morning
Least-toxic management, in order
- 1Collars — Ring each transplant with a collar pushed 1-2 inches into the soil and standing at least 3 inches tall to physically block the caterpillars.
- 2Gritty barriers — Surround stems with crushed oyster shell, sand, or diatomaceous earth.
- 3Handpick at night — Search the soil surface after dark and drop cutworms into soapy water.
- 4Cultivate soil — Till in spring or fall to expose overwintering larvae to freezing and predators.
When to escalate
If collars and barriers are in place but seedlings keep disappearing, confirm the culprit by scouting at night, since slugs and other pests cause similar damage. Contact your regional Extension office for identification help before applying any product.
✔ Set out transplants a little later, once soil warms, so plants grow past the most vulnerable seedling stage faster.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- University of Minnesota Extension — Cutworms — Cutworm appearance, C-shape behavior, night feeding, and cut-at-soil-line damage
- University of Massachusetts Extension — Insect Management in the Home Vegetable Garden — Collar dimensions and placement, gritty barriers, and tilling to disrupt overwintering