# Caterpillar

> The larval stage of moths and butterflies (order Lepidoptera); on cannabis, leaf-chewers, stem borers and bud-boring species whose frass seeds bud rot.

- Canonical: https://genetixbay.com/knowledge/glossary/caterpillar.html
- Also written: caterpillars, worms, larvae, European corn borer, Ostrinia nubilalis, hemp borer
- 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"

A caterpillar is the larva of a moth or butterfly (order Lepidoptera). Several groups attack cannabis: leaf chewers such as loopers and armyworms, stem borers such as the European corn borer (*Ostrinia nubilalis*) and the [hemp](https://genetixbay.com/knowledge/glossary/hemp.md) borer (*Grapholita delineata*), and bud feeders such as the [corn earworm](https://genetixbay.com/knowledge/glossary/corn-earworm.md) (*Helicoverpa zea*). Outdoor and greenhouse crops carry most of the risk; sealed indoor rooms rarely see them.

## In practice

Signs are ragged holes in leaves, wilting branch tips above a borer's entry hole, and above all [frass](https://genetixbay.com/knowledge/glossary/frass.md) (droppings) inside buds. Wet frass and chewed tissue give *Botrytis* an easy entry, so one caterpillar can rot a whole [cola](https://genetixbay.com/knowledge/glossary/cola.md). Growers scout for moths at dusk, eggs on leaf surfaces and fresh frass. *[Bacillus thuringiensis](https://genetixbay.com/knowledge/glossary/bacillus-thuringiensis.md)* products, which must be eaten to work, are the standard biological option and work best on young larvae before they bore into buds. Netting and [pheromone traps](https://genetixbay.com/knowledge/glossary/pheromone-trap.md) help outdoors. Check what is registered for cannabis locally.

## Don't confuse with

- **Fungus gnat larvae**: tiny clear maggots in the medium, not on the plant.
- **Cutworms**: a caterpillar group that hides in soil by day and severs [seedlings](https://genetixbay.com/knowledge/glossary/seedling.md) at the base.
- **Slug damage**: holes plus slime trails, usually low on the plant.

## Related terms

[Corn earworm](https://genetixbay.com/knowledge/glossary/corn-earworm.md), [Cutworm](https://genetixbay.com/knowledge/glossary/cutworm.md), [Bacillus thuringiensis](https://genetixbay.com/knowledge/glossary/bacillus-thuringiensis.md), [Botrytis](https://genetixbay.com/knowledge/glossary/botrytis.md), [Scouting](https://genetixbay.com/knowledge/glossary/scouting.md)

## Read more

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

## Sources

1. Oregon State University Extension. Corn earworm management in hemp (EM 9626). https://extension.oregonstate.edu/catalog/em-9626-corn-earworm-management-hemp
2. Cranshaw, W. Hemp pests (CSU, 2020). https://webdoc.agsci.colostate.edu/bspm/InsectInformation/Talks2020/HempPests.pdf