# Cutworm

> Moth caterpillars of the family Noctuidae, such as the black cutworm (Agrotis ipsilon), that hide in soil by day and chew through seedling stems at night.

- Canonical: https://genetixbay.com/knowledge/glossary/cutworm.html
- Also written: cutworms, black cutworm, Agrotis ipsilon, Agrotis
- Glossary category: Pests and diseases · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Cutworms are the larvae of several noctuid moths, notably the black cutworm (*Agrotis ipsilon*). They are plump, greasy-looking grey to brown caterpillars, up to about 4-5 cm long, that curl into a C-shape when disturbed. They hide in the top layer of soil by day and feed at night.

## In practice

The giveaway is a [seedling](https://genetixbay.com/knowledge/glossary/seedling.md) or young [transplant](https://genetixbay.com/knowledge/glossary/transplanting.md) cut clean through at or just below the soil line overnight, often with the top lying beside it. Digging gently around the stem usually turns up the culprit. They are an outdoor and greenhouse problem, worst in fields that were weedy or grassy the season before. Simple stem collars of card or plastic pushed into the soil around transplants stop most damage. Hand-picking at night with a torch works in small gardens. [Entomopathogenic nematodes](https://genetixbay.com/knowledge/glossary/steinernema-feltiae.md) and *[Bacillus thuringiensis](https://genetixbay.com/knowledge/glossary/bacillus-thuringiensis.md)* are biological options. Check what is registered for cannabis locally.

## Don't confuse with

- **Damping-off**: the stem rots and pinches at the base; it is not chewed through.
- **Slugs**: slime trails and ragged leaf holes.
- **Corn earworm**: feeds in buds later in the season.

## Related terms

[Caterpillar](https://genetixbay.com/knowledge/glossary/caterpillar.md), [Corn earworm](https://genetixbay.com/knowledge/glossary/corn-earworm.md), [Damping-off](https://genetixbay.com/knowledge/glossary/damping-off.md), [Bacillus thuringiensis](https://genetixbay.com/knowledge/glossary/bacillus-thuringiensis.md), [Steinernema feltiae](https://genetixbay.com/knowledge/glossary/steinernema-feltiae.md)

## Read more

- [Caterpillars on cannabis: species, degree-days and control](https://genetixbay.com/knowledge/pests/caterpillars.md)

## Sources

1. Cranshaw, W. Hemp pests (CSU, 2020). https://webdoc.agsci.colostate.edu/bspm/InsectInformation/Talks2020/HempPests.pdf