Bud rot is a common fungal disease that affects cannabis flowers, and it can quickly ruin a significant portion of a crop. This infection, often caused by the fungus Botrytis cinerea, typically starts deep inside the dense flower structure where moisture is trapped. Because the infection begins internally, smell often serves as the earliest warning sign before any obvious visual damage appears on the surface. Early detection is important for managing the spread of this destructive gray mold.
Identifying the Odor: Describing the Smell of Bud Rot
The characteristic scent of bud rot is a sharp, unpleasant departure from the healthy, fragrant aroma of flowering cannabis. Instead of the expected sweet, earthy, or pungent notes, an infected bud emits a noxious odor that indicates active decay.
The distinct scent profile is most commonly described as a mixture of musty mildew, wet cardboard, or decaying organic matter. Some people report a sharp, ammonia-like quality, especially as the infection becomes more advanced and the breakdown of proteins increases.
This foul scent contrasts strongly with the normal drying plant material, which may have a faint grassy smell that quickly dissipates. The musty, decaying smell of bud rot tends to linger and intensify, signaling a fungal infestation rather than harmless drying leaves. Catching this odor early, particularly when inspecting dense flower clusters, can save the rest of the plant from spore contamination.
Visual and Tactile Confirmation of Infection
While the smell is often the first indicator, visual and tactile inspection provides confirmation of a Botrytis cinerea infection. A telltale visual sign is the sudden wilting or yellowing of a single leaf or small cluster of sugar leaves protruding from a cola.
If an infection is present, the affected area will show discoloration, turning from a healthy green to patches of gray, brown, or black. As the rot progresses, a grayish, fuzzy mold may become visible on the surface, which is the fungus producing spores. This fuzzy growth is sometimes white in its early stages before darkening as the infection progresses.
The texture of an infected bud changes drastically, offering a tactile confirmation of the rot. A healthy flower is firm and resilient, but a bud with rot will feel spongy or mushy when gently squeezed. When an infected section is pulled apart, it will crumble easily, revealing the dark, moldy mess that has consumed the interior of the flower.
Environmental Triggers and Prevention Strategies
The primary factor is high humidity, as the spores need moisture to germinate and spread. Humidity levels consistently above 50% during the flowering stage create a favorable breeding ground for the pathogen.
Poor air circulation is another major trigger, as stagnant air allows moisture to settle and accumulate on the plant surfaces, creating microclimates of high humidity within the dense foliage. Temperature fluctuations, especially rapid shifts between warm and cool conditions, can also stress plants and increase their susceptibility. The optimal temperature range for the fungus’s growth is typically between 68°F and 77°F (20°C and 25°C).
Maintaining relative humidity between 40% and 60% during the flowering phase is an effective control measure, often requiring the use of dehumidifiers. Robust ventilation, including oscillating fans and exhaust systems, ensures continuous air movement across and through the plant canopy, preventing moisture buildup.
Strategic pruning is also important, as removing excess foliage improves airflow and light penetration deep within the plant. Proper spacing between plants prevents overcrowding, which reduces the formation of high-humidity pockets and minimizes the risk of spores spreading from plant to plant. Regular inspection of the densest buds, especially after periods of high moisture, allows for early intervention and removal of any suspected areas.