# Generation time

> The average time from a female's birth to the birth of her offspring; at a set temperature it fixes how often a pest population multiplies.

- Canonical: https://genetixbay.com/knowledge/glossary/generation-time.html
- Also written: mean generation time, generation length
- 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"

Generation time is the mean age at which females produce their offspring, from a [life table](https://genetixbay.com/knowledge/glossary/life-table.md). It is longer than egg-to-adult development, because females need a pre-oviposition period and lay over many days. For [two-spotted spider mites](https://genetixbay.com/knowledge/glossary/two-spotted-spider-mite.md) it is roughly one to two weeks at 25 C in lab studies, shorter in heat.

## In practice

Generation time drives control intervals. A spray or release that misses eggs must be repeated before the survivors mature and lay, which means within one egg-plus-immature period at your temperature. [Degree-day](https://genetixbay.com/knowledge/glossary/degree-day.md) thresholds let you convert one temperature's generation time to another's.

## Don't confuse with

- **Doubling time**: how long numbers take to double, much shorter than a generation.

## Related terms

[Intrinsic rate of increase (r_m)](https://genetixbay.com/knowledge/glossary/intrinsic-rate-of-increase.md), [Degree-day](https://genetixbay.com/knowledge/glossary/degree-day.md), [Life table](https://genetixbay.com/knowledge/glossary/life-table.md)

## Read more

- [Temperature, humidity and pest population growth in cannabis: every major pest compared](https://genetixbay.com/knowledge/pests/temperature-humidity-and-pest-population-growth.md)

## Sources

1. Birch, L.C., 1948. The intrinsic rate of natural increase of an insect population. Journal of Animal Ecology 17:15-26. https://doi.org/10.2307/1605
2. UC IPM. Degree-Days: About Degree-Days. University of California ANR. https://ipm.ucanr.edu/WEATHER/ddconcepts.html