DiseasesUrgent — act today
Bud Rot (Botrytis) in Cannabis
Bud rot (Botrytis cinerea) is the worst disease in cannabis flowering. It rots buds from the inside out, turning flowers into gray mush.
What it looks like
- ●Gray/brown fuzzy growth inside buds
- ●Once-dense buds feel mushy or hollow
- ●Surrounding leaves yellow and curl
- ●A musty smell from affected buds
Quick diagnostic checks
1Cut out ANY affected bud with 2" of clean tissue around it — bag and trash
2Lower humidity to 40% immediately
3Increase airflow at canopy level
4Harvest early if rot is spreading — better less weight than no weight
Causes ranked by likelihood
1. High humidity in flower
Most commonSigns
- ●RH above 55% during flower
- ●Wet/cold nights (outdoor)
Fix
- ✓Keep flower humidity at 40-50% max
- ✓Bring outdoor plants inside for rainy days
- ✓Run dehumidifier at night when temps drop
2. Stagnant air in dense colas
Most commonSigns
- ●Big dense buds with no airflow through them
- ●Foxtail growth trapping moisture
Fix
- ✓Canopy-level oscillating fans — air should move through every bud
- ✓Defoliate aggressively in flower (bottom ⅓)
3. Caterpillar damage leading to rot
CommonSigns
- ●Frass (worm poop) in buds
- ●Growing outdoors
Fix
- ✓Apply BT throughout flower to prevent caterpillar damage
⚠️When to worry
ALWAYS. Bud rot is the #1 cause of lost flower harvests. Act within hours of spotting.
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