# Bud rot check

> Routine inspection of dense colas in late flower, at harvest and during drying and curing for signs of grey mould (Botrytis cinerea) and other rots.

- Canonical: https://genetixbay.com/knowledge/glossary/bud-rot-check.html
- Also written: mold check, mould check, checking for bud rot, checking for mold, rot check, botrytis check
- Glossary category: Harvest, drying and curing · 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 bud rot check is a deliberate inspection of buds for mould, mainly [grey mould](https://genetixbay.com/knowledge/glossary/botrytis.md) caused by *Botrytis cinerea*, which rots dense flowers from the inside out. It belongs in late flower, at harvest, during the dry and in the first weeks of the cure, because the fungus thrives in humid, still air and tightly packed buds.

## In practice

What to look for:
- a single [sugar leaf](https://genetixbay.com/knowledge/glossary/sugar-leaf.md) or bract cluster turning dry, brown or grey while the rest is green;
- soft, mushy, brown tissue inside a [cola](https://genetixbay.com/knowledge/glossary/cola.md) near the stem;
- grey, fuzzy growth, sometimes with dusty spores;
- a musty or damp smell in the room or a jar.

How to check: gently part the largest colas, especially top colas and buds near the stem, and look in at the core. Use a loupe on suspicious spots. In jars, empty a sample of buds onto a tray rather than looking through the glass.

If you find it, cut the affected bud out with a margin, bag it inside the room to avoid spreading spores, and don't smoke or process mouldy material. Then fix the cause: [RH](https://genetixbay.com/knowledge/glossary/relative-humidity.md) in late flower around 40-50%, air through the canopy, a [drying room](https://genetixbay.com/knowledge/glossary/drying-room.md) at about 55-62% RH, not higher.

## Don't confuse with

- **Powdery mildew**: white powder on leaf surfaces.
- **Natural senescence**: yellowing leaves, not brown, mushy buds.
- **Pistil browning**: normal ageing of stigmas.

## Related terms

[Botrytis](https://genetixbay.com/knowledge/glossary/botrytis.md), [Cola](https://genetixbay.com/knowledge/glossary/cola.md), [Drying room](https://genetixbay.com/knowledge/glossary/drying-room.md), [Curing](https://genetixbay.com/knowledge/glossary/curing.md), [Jeweler's loupe](https://genetixbay.com/knowledge/glossary/jewelers-loupe.md)

## Read more

- [Botrytis (bud rot / grey mould) in cannabis](https://genetixbay.com/knowledge/diseases/botrytis-bud-rot.md)
- [Drying cannabis: the 60/60 method and water activity](https://genetixbay.com/knowledge/harvest-cure/drying.md)

## Sources

1. Punja ZK. 2021. Emerging diseases of Cannabis sativa and sustainable management. Pest Management Science 77:3857-3870. https://pmc.ncbi.nlm.nih.gov/articles/PMC8451794/