Botrytis cinerea is a fungus that causes grey mould, called bud rot on cannabis. It attacks dense flowers from the inside, usually starting near the stem of a cola where moisture is trapped. Infected tissue turns brown and mushy; sugar leaves wilt and yellow; grey, fuzzy spores appear as it progresses. It also causes stem cankers and damping-off.
In practice
The classic sign is a single dried, discoloured leaf sticking out of an otherwise healthy cola. Pulling it reveals brown rot inside. Botrytis loves cool nights, high humidity, dew, poor airflow and wounds such as caterpillar damage. Indoors, controlling humidity and night-time dew point late in flower is the main prevention; outdoors, open-structured cultivars and early harvest before autumn rain help. Infected buds should be cut out with a margin, bagged in the room and removed; do not shake spores onto the rest of the crop. Mouldy buds should never be consumed.
Don't confuse with
- Powdery mildew: white surface powder on leaves first, not internal rot.
- Corn earworm damage: holes and frass, often with botrytis following.
- Natural senescence: yellowing fan leaves late in flower, with healthy bud tissue.
The dense, elongated cluster of flowers that forms at the end of a stem or branch; the main cola tops the leader.A small leaf growing from within the flower cluster, often coated in trichomes, which is trimmed off and commonly kept for processing.A fungal disease caused by Sclerotinia sclerotiorum that girdles stems with cottony white growth and hard black sclerotia, killing branches above the lesion.Dew point is the temperature at which air becomes saturated and water starts condensing; when leaves or buds cool to it, free water forms and mould risk jumps.Pest and disease prevention by changing how the crop is grown, such as humidity, airflow, spacing, watering and cultivar choice, so pests and pathogens struggle to establish.A fungal disease, on cannabis caused mainly by Golovinomyces ambrosiae, that grows as white powdery patches on leaves and buds and thrives in moderate humidity.Helicoverpa zea, a moth caterpillar that bores into developing cannabis flowers outdoors, leaving frass that triggers bud rot; growers call it budworm.The programmed ageing and breakdown of leaves and other tissues, in which the plant recycles nutrients (especially nitrogen) from old leaves to developing flowers and seeds.Cleaning and disinfecting rooms, tools, containers, irrigation and people's clothing so that pests and pathogens are not carried from plant to plant or crop to crop.The everyday word for visible fungal growth; on cannabis it covers several distinct diseases, mainly bud rot (Botrytis cinerea) and powdery mildew (Golovinomyces ambrosiae).
