Budrot (Botrytis): A Common Fungus Affecting Cannabis Plants

Budrot, also known as Botrytis, brown rot, or grey mold, is a widespread fungus that impacts both indoor and outdoor crops under specific conditions. Airborne Botrytis spores are omnipresent year-round and can infect various plant species, targeting flowers, leaves, and stems.

Factors Increasing Budrot Vulnerability​

Growers utilizing sea of green, perpetual harvest, remote grows, outdoor, or multiple strains with distinct flowering periods should closely monitor for Botrytis near harvest time. Outdoor growers, in particular, must be vigilant about weather conditions such as rain, morning dew, frost, and cool fall nights, as they may heighten the risk of budrot and powdery mildew.

Fully developed marijuana buds create ideal conditions for spore germination: warm and moist plant tissues. Botrytis typically attacks the largest and densest buds first, as they provide optimal germination conditions. Weaker plants are also susceptible to rapid infection.

Identifying and Preventing Budrot​

Budrot can quickly spread and ruin a crop if left unchecked. The fungus thrives in warm and humid environments, with relative humidity above 50%. Lowering humidity, improving ventilation, and ensuring adequate air circulation can help prevent infection.

A moldy smell in the grow room may indicate a Botrytis infection. Once a cola is infected, the fungus can spread rapidly, turning entire colas to brown mush and producing spores that attack nearby colas. Ventilation may inadvertently disseminate viable spores throughout the room.

Measures to Prevent Budrot in Late Flowering Stages​

To prevent budrot during the final stages of flowering, consider the following measures:

• Prune undergrowth in the early veg and flower stages to promote air circulation.
• Use HEPA filters for room and intake air sources.
• Introduce low levels of ozone into the room air to combat pollen, powdery mildew, and other airborne spores.
• Lower room humidity by warming nighttime air, venting frequently, or using a dehumidifier.
• Decrease watering cycles and amounts to reduce room humidity.
• Inspect large, dense colas periodically for brown and moldy tissues.
• Remove fan leaves in the days leading up to harvest to improve air circulation.
• Apply Serenade, an organic, EPA/USDA-approved treatment for Botrytis, powdery mildew, and downy mildew, as a preventative measure.

Handling Budrot Infections​

If budrot is detected, immediately remove and isolate the infected buds from the grow room. Harvest the infected colas and quickly dry them. Take steps to reduce room humidity and inspect the entire crop for signs of infection and damage.

If multiple rotting colas are discovered, consider harvesting early, as spores may have spread and could be germinating within other colas.

Salvaging Budrot-Infected Colas​

While not recommended, it is possible to salvage infected colas. Remove the infected colas, trim out the infection, and quick-dry the remaining buds. Re-inspect the buds to ensure they no longer smell moldy. However, smoking infected buds is not advised.