Bud rot is a destructive fungal infection, most notably affecting the dense flower structures of cannabis. It is caused by the fungus Botrytis cinerea, also known as gray mold, which kills and consumes plant tissue. This infection compromises the structural integrity and quality of the affected material. While bud rot does have a smell, relying on scent alone is highly unreliable and often indicates the infection is already widespread.
The Specific Smell of Bud Rot
A noticeable odor is a late-stage warning that fungal decomposition is underway. As Botrytis cinerea breaks down the internal structure, it releases organic compounds that create a recognizable scent. This odor is typically described as an unpleasant mix of musty, damp, or stale air.
The decay may also generate a sharp, decaying smell, sometimes likened to old socks, wet cardboard, or rotting vegetables. This distinct scent contrasts sharply with the plant’s healthy, aromatic profile. The natural fragrance can mask the moldy smell, meaning the rot often goes undetected until it has progressed significantly.
The fungus usually begins deep within the dense core of the flower, where moisture is trapped and airflow is minimal. By the time the smell permeates the air, the fungal mycelium has likely consumed substantial interior tissue. A moldy odor signifies an advanced infection rather than an early warning.
Visual and Textural Signs of Infection
Non-olfactory signs are the earliest and most reliable indicators of a Botrytis infection. The first visible symptoms are localized, often appearing as small, brown, or yellow spots on the sugar leaves protruding from the flower cluster. These infected leaves wilt quickly and pull out easily because the fungus has destroyed the connecting tissue.
As the infection spreads, the affected area changes color, turning gray, brown, or black. The characteristic sign is a fuzzy, gray or brownish mold growth on the surface of the flower. This gray mass is a collection of fungal spores, which are easily dislodged and spread by air currents.
The texture of the infected bud changes, becoming soft, mushy, or slimy to the touch, distinguishing it from healthy, firm flowers. Since the rot starts internally, gently inspect the densest parts of the plant near the main stem where moisture accumulates. Detecting these changes allows for earlier intervention than waiting for the scent to become obvious.
Preventing the Conditions That Promote Rot
Botrytis cinerea spores require specific environmental conditions to germinate, primarily high humidity and poor air circulation. Prevention focuses on disrupting the moisture-rich microclimates the fungus needs to thrive.
Key Prevention Strategies
- Maintain relative humidity levels below 50 percent, especially during the flowering stage when plant structures are dense.
- Ensure excellent air movement throughout the growing space using oscillating fans to prevent pockets of still, moist air from forming around flowers.
- Prune lower, non-productive foliage and ensure adequate spacing between plants to increase air circulation within the canopy.
- Practice sanitation by quickly removing any dead or decaying plant material to reduce the number of available fungal spores.
- Water plants at the base and avoid wetting the flowers, particularly late in the day, to minimize the duration of surface wetness.