Skip to content
transplantsUpdated Apr 2026

Something is cutting off my seedlings at the base overnight — what is it?

Cutworms — fat gray or brown caterpillars that live in the soil and feed at night — cut young stems at or just below the soil surface, and a simple collar around each stem can stop them.

Cutworms are the larvae of several moth species. They spend the day curled up 1–2 inches below the soil surface, then emerge at night to feed. They don't eat the leaves — they cut the stem at the soil line and move on. A tray of 20 transplants can lose a third of its plants in a single night. The sign is a cleanly severed stem lying next to its hole in the ground.

The most reliable control is a physical collar around each transplant stem. This can be a toilet paper roll cut in half, a tin can with the bottom removed, a cup with the bottom cut out, or a ring of cardboard. Press it 1 inch into the soil and leave 2 inches above. The cutworm can't navigate around it. This approach works essentially every time and requires no chemicals.

Diatomaceous earth (food-grade) sprinkled in a ring around transplants can deter cutworms, though it needs reapplication after rain. Beneficial nematodes (Steinernema carpocapsae) applied to moist soil can reduce cutworm populations over time but work best as a preventive measure in soil where cutworms have been a recurring problem.

If you dig around a cut plant the morning after the damage, you'll often find the cutworm curled up in the soil within 2–4 inches. Hand-picking is satisfying and effective when you can find them. The problem tends to be worst in the first 2–3 weeks after transplanting; once stems are more than pencil-thick, cutworms typically move on to easier targets.

Connected