Bud Rot

Bud rot, caused by the fungal pathogen Botrytis cinerea, is the most devastating disease in flowering cannabis and the primary cause of harvest loss in outdoor and greenhouse production. The fungus exists ubiquitously in air and soil, with spores ready to infect any cannabis flower when conditions allow. Optimal conditions for bud rot: cool temperatures 60-70°F (15-21°C), humidity above 60% RH, dense bud structure that traps moisture internally, poor airflow within the canopy, and physical damage to bud tissue (broken stems, insect damage, pruning wounds). Infection sequence: spores land on bud surface and penetrate via moisture-laden calyxes; mycelium colonizes the dense bud interior where humidity remains high; affected tissue dies and turns gray-brown; under continued moisture, gray fuzzy sporulation appears on the bud surface; spores release into the air and infect adjacent buds within 6-24 hours. Visible symptoms: white or yellow leaves wilting in healthy-looking dense buds (the first warning sign), bud cores feeling soft when squeezed, brown discoloration visible by pulling apart the affected cola, and finally gray fuzzy mold growth on the bud exterior. Treatment: there is no recovery from established bud rot — affected sections must be removed immediately and bagged for disposal (not composted, which spreads spores). Surrounding buds should be inspected and any showing softness removed. The remainder of the plant should be harvested early to prevent further loss. Prevention: maintain humidity below 50% RH during flowering (especially weeks 6+), aggressive defoliation to expose bud sites to airflow, oscillating fans throughout the canopy, lollipopping to eliminate dense lower bud zones, and selecting mold-resistant strains for outdoor and humid climates (most landrace sativas tolerate humidity better than dense indica hybrids).