Cannabis flower is hospitable to botrytis (bud rot) and powdery mildew when humidity exceeds ~55% and airflow is poor. Late flower is the highest risk because dense buds trap moisture.

Humidity targets. Aim for 50–55% RH late veg → 45–50% RH early flower → 40–45% RH mid/late flower. Dehumidifiers are the most reliable lever.

Airflow. Oscillating fans creating gentle leaf movement across the canopy disrupt the boundary layer where pathogens establish. Both above and below canopy.

Defoliation. Strategic removal of large fan leaves blocking inner-canopy airflow in mid flower. Don't strip — selectively open up the airflow path.

Inspect daily in the last 3 weeks. Bud rot starts inside a dense cola and turns leaves yellow before grey fuzzy mold becomes visible. Cut out affected sections immediately with clean scissors, bag, dispose — do not compost.

Can I save a partially molded plant?+
Cut out the affected bud + a healthy buffer. Inspect the rest of the plant carefully — moldy material in cured flower is a health risk. When in doubt, cut more than you think.