# What is eating holes in my leaves?

> Holes in cannabis leaves are usually chewing pests, and the clue left behind names them. Dark frass pellets mean caterpillars; silvery slime trails mean slugs or snails; ragged margins on outdoor edge plants mean grasshoppers; a seedling cut through at the soil line means cutworms. Indoors, chewers are rare: holes there are more often dead, dried tissue from nutrient or burn spots falling out. Check at night with a torch.

- Canonical: https://genetixbay.com/knowledge/answers/holes-in-leaves.html
- Topic: Pests · Type: Troubleshooting
- Evidence: Established · Status: Draft: awaiting expert review
- Full article: [Caterpillars on cannabis: species, degree-days and control](https://genetixbay.com/knowledge/pests/caterpillars.md)
- Also asked as: Why are there holes in my cannabis leaves? | Something is chewing my leaves | Leaf damage from bugs outdoors | Ragged holes in leaves overnight | Holes in leaves indoors but no bugs
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Short answer

Holes in cannabis leaves mean a chewer, and the evidence it leaves tells you which: [frass](https://genetixbay.com/knowledge/glossary/frass.md) for caterpillars, slime for slugs, ragged edges for [grasshoppers](https://genetixbay.com/knowledge/glossary/grasshopper.md), cut stems for [cutworms](https://genetixbay.com/knowledge/glossary/cutworm.md). Indoors, holes without frass are usually dead spots dropping out, not pests. *Established*.

## Why

Caterpillars leave droppings. Young larvae chew small holes in leaves; older [corn earworm](https://genetixbay.com/knowledge/glossary/corn-earworm.md) larvae, up to about 25 mm (1 in), bore into buds, and their frass lets [bud rot](https://genetixbay.com/knowledge/glossary/botrytis.md) in [1][3].

Outdoor chewers come from the surroundings. Grasshoppers move in from field edges in dry summers, and cutworms hide in soil by day and cut young stems at night; both are listed among [hemp](https://genetixbay.com/knowledge/glossary/hemp.md) pests [2].

Slugs and snails feed at night and in wet weather, leaving ragged holes and slime on [seedlings](https://genetixbay.com/knowledge/glossary/seedling.md) and low leaves.

[Leafminers](https://genetixbay.com/knowledge/glossary/leafminer.md) make tunnels, not holes: pale winding trails inside the leaf [4].

Indoors, chewing pests are uncommon and usually arrive through open intakes or doors [1].

## The numbers

| Clue | Likely cause | Where |
|---|---|---|
| Holes plus dark frass pellets | Caterpillars | Outdoors mostly; buds in flower |
| Ragged holes plus slime trails | Slugs, snails | Seedlings, low leaves, after rain |
| Missing leaf margins, edge plants first | Grasshoppers | Outdoors, dry summers |
| Seedling cut at soil line | Cutworm | Fresh outdoor [transplants](https://genetixbay.com/knowledge/glossary/transplanting.md) |
| Pale winding trails | Leafminer | [Fan leaves](https://genetixbay.com/knowledge/glossary/fan-leaf.md) |
| Brown-edged holes, no frass | Dead spots falling out | Indoors |

## What to do

1. Look on and under leaves at dusk and after dark with a torch.
2. Search for frass, slime, larvae and cut stems.
3. Hand-pick caterpillars, slugs and cutworms; bag damaged bud sections.
4. Use stem collars on transplants and fine netting where practical.
5. From early flower, scout upper [colas](https://genetixbay.com/knowledge/glossary/cola.md) twice weekly for eggs and frass.
6. Indoors with no frass, check nutrients, [pH](https://genetixbay.com/knowledge/glossary/ph.md) and spray or [light burn](https://genetixbay.com/knowledge/glossary/light-stress.md).

## Common mistakes

- Spraying before identifying the culprit.
- Ignoring leaf holes in late summer until buds rot.
- Using Bt on large larvae already inside buds.
- Blaming insects for nutrient spots indoors.

## Related

- Full article: [Caterpillars and budworms on cannabis](https://genetixbay.com/knowledge/pests/caterpillars.md)
- Answer: [What can I spray in flower?](https://genetixbay.com/knowledge/answers/what-can-i-spray-in-flower.md)
- Article: [Rust or brown spots on leaves](https://genetixbay.com/knowledge/diagnosis/rust-spots.md)
- Terms: [slugs and snails](https://genetixbay.com/knowledge/glossary/slugs-and-snails.md) · [cutworm](https://genetixbay.com/knowledge/glossary/cutworm.md) · [grasshopper](https://genetixbay.com/knowledge/glossary/grasshopper.md) · [leafminer](https://genetixbay.com/knowledge/glossary/leafminer.md)

## Follow-up questions

**What is eating my cannabis leaves at night?** Leaves of cannabis eaten overnight point to night feeders: slugs and snails, which leave ragged holes and silvery slime trails, caterpillars, which leave dark frass pellets, and cutworms, which chew young stems through at the soil line. Go out an hour or two after dark with a torch, especially after rain, and look on and under the leaves and around the stem base.

**Why are there holes in my leaves indoors with no bugs?** Holes in indoor cannabis leaves with no bugs and no frass are usually dead tissue falling out, not feeding. Brown or rust spots from nutrient problems, spray burn or light burn dry out and crack away, leaving holes with brown edges. Chewing pests are uncommon indoors and usually arrive through open intakes or doors. Check leaf undersides with a lens before blaming insects.

**Do I need to treat for caterpillars if I see holes?** A few caterpillar holes in fan leaves cost little, but they warn you that moths are laying eggs, and in flower the larvae bore into buds and start bud rot. Hand-pick larvae at dusk or dawn, scout upper colas for eggs and frass from early flower, and use fine netting where practical. Bt works only on small larvae, under about 12 mm (0.5 in).

## 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
3. Utah State University Extension. Corn Earworm (hemp). https://extension.usu.edu/planthealth/ipm/notes_ag/hemp-corn-earworm
4. Michigan State University Extension. Managing greenhouse insects. https://www.canr.msu.edu/news/managing_greenhouse_insects