Mold (mould in British and Canadian English) is a loose word for fungi that grow as visible threads and spores. Growers use "mold" and "mildew" for very different problems, so the first step is naming the organism. On living cannabis the main ones are bud rot (Botrytis cinerea), powdery mildew (Golovinomyces ambrosiae), white mould (Sclerotinia sclerotiorum) and, outdoors, downy mildew. After harvest, Penicillium and Aspergillus species can grow on buds that are dried or stored too wet.
In practice
Each has a different cause and fix: bud rot follows cool, humid, stagnant conditions inside dense colas; powdery mildew spreads in moderate humidity without leaf wetness; storage moulds follow high water activity in the jar. Some Aspergillus species are a health concern for people with weakened immunity, which is one reason many markets test for them. Mouldy flower should be discarded, not trimmed and smoked. Prevention beats every cure: humidity control, airflow and a proper dry.
Don't confuse with
- Trichomes: glittering resin heads, not fuzzy growth.
- Total yeast and mold (TYM): a lab count, not a single organism.
Botrytis cinerea, the fungus behind bud rot or grey mould, which rots dense colas from the inside in cool, humid conditions late in flower.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.A fungal disease caused by Sclerotinia sclerotiorum that girdles stems with cottony white growth and hard black sclerotia, killing branches above the lesion.An oomycete leaf disease of cannabis, historically attributed to Pseudoperonospora cannabina, causing yellow patches above and grey-purple fuzz under leaves in cool, wet weather.The dense, elongated cluster of flowers that forms at the end of a stem or branch; the main cola tops the leader.A 0-1 measure of how freely available the water in a material is; for dried cannabis flower the accepted range is about 0.55-0.65 aw.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 hair-like outgrowth of the plant's skin; in cannabis the glandular types make and store the resin holding cannabinoids and terpenes.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.
