Mold & rot prevention

Mold and rot are among the most destructive issues in cannabis cultivation, capable of ruining entire crops if left unchecked. Preventing these problems requires a proactive approach, combining environmental control, early detection, and effective treatments. This guide provides comprehensive strategies for keeping your cannabis plants mold- and rot-free.

1. Common Types of Mold and Rot

  • Powdery Mildew:
    • Identification: White, powdery spots on leaves and stems.
    • Effects: Reduces photosynthesis and weakens plants.
  • Botrytis (Bud Rot):
    • Identification: Gray or brown rot inside buds, often detected too late.
    • Effects: Causes buds to turn mushy and decay.
  • Root Rot:
    • Identification: Brown, slimy roots with a foul odor.
    • Effects: Stunts growth and often kills plants if not addressed.

2. Causes of Mold and Rot

  • High Humidity: Encourages fungal growth, especially above 70% relative humidity.
  • Poor Air Circulation: Creates stagnant air, which allows mold spores to settle and spread.
  • Overwatering: Leads to excessive moisture in the root zone and invites root rot.
  • Dense Canopy: Blocks airflow and traps moisture around leaves and buds.

3. Prevention Strategies

  • Humidity Control:
    • Keep humidity levels within optimal ranges:
      • Vegetative Stage: 40–70% relative humidity.
      • Flowering Stage: 40–50% relative humidity.
    • Use dehumidifiers to reduce excess moisture in the grow area.
  • Ventilation and Airflow:
    • Install oscillating fans to circulate air throughout the grow space.
    • Ensure exhaust systems remove stale air and maintain negative pressure.
  • Pruning and Defoliation:
    • Remove lower leaves and excess foliage to improve airflow through the canopy.
    • Maintain proper spacing between plants to reduce crowding.
  • Watering Practices:
    • Avoid overwatering; let the top layer of soil dry out between waterings.
    • Water early in the day to allow moisture to evaporate by night.

4. Early Detection

  • Inspect plants regularly for signs of mold or rot, especially in dense buds and lower foliage.
  • Use magnifiers to spot powdery mildew or other early-stage issues.

5. Treatment Options

  • Organic Sprays:
    • Neem oil or potassium bicarbonate for powdery mildew.
    • Biological fungicides like Bacillus subtilis for general fungal prevention.
  • Bud Rot:
    • Carefully remove and dispose of infected buds to prevent spread.
    • Quarantine affected plants to protect the rest of the crop.
  • Root Rot:
    • Flush roots with hydrogen peroxide solution to kill pathogens.
    • Improve drainage and aeration in the root zone.

6. Post-Harvest Precautions

  • Drying: Maintain a humidity level of 45–55% in the drying area to prevent mold growth on harvested buds.
  • Curing: Use airtight jars with humidity packs to control moisture during curing.
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