# Instar

> A developmental stage between two moults of an insect larva or nymph; control tactics often work only on early instars.

- Canonical: https://genetixbay.com/knowledge/glossary/instar.html
- Also written: instars, larval instar, nymphal instar, first instar, early instar
- 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"

An instar is the stage of an insect between one moult and the next. A caterpillar typically passes through five or six larval instars before pupating; an [aphid](https://genetixbay.com/knowledge/glossary/aphid.md) has four nymphal instars. Each instar is larger and, often, harder to kill. Oregon State Extension advises targeting [corn earworm](https://genetixbay.com/knowledge/glossary/corn-earworm.md) while larvae are small, before they bore into [hemp](https://genetixbay.com/knowledge/glossary/hemp.md) buds.

## In practice

Instar matters for timing. Bt-class sprays act when eaten and work best on first and second instars still feeding on the surface; late instars inside [colas](https://genetixbay.com/knowledge/glossary/cola.md) are out of reach. Scout for eggs and tiny larvae after moth flights, not for damage.

## Don't confuse with

- **Generation**: egg to egg, several instars long.
- **Pupa**: the non-feeding stage after the last larval instar.

## Related terms

[Crawler](https://genetixbay.com/knowledge/glossary/crawler.md), [Life table](https://genetixbay.com/knowledge/glossary/life-table.md), [Bacillus thuringiensis](https://genetixbay.com/knowledge/glossary/bacillus-thuringiensis.md)

## Read more

- [Caterpillars on cannabis: species, degree-days and control](https://genetixbay.com/knowledge/pests/caterpillars.md)
- [Budworms on cannabis: corn earworm and tobacco budworm in numbers](https://genetixbay.com/knowledge/pests/budworms-corn-earworm.md)

## Sources

1. Shrestha, G., 2022. Corn earworm management in hemp (EM 9626). Oregon State University Extension. https://extension.oregonstate.edu/catalog/em-9626-corn-earworm-management-hemp