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Pest & Disease Library · Solutions

Powdery Mildew Control in Cannabis

Powdery mildew is a white fungal coating that spreads across leaves and reduces photosynthesis, vigour, and crop quality — even in dry weather. This page covers powdery mildew in cannabis & hemp.

Common crops affected

Why it matters

It spreads fast in crowded canopies, cuts photosynthesis and yield, and downgrades fruit; in high-value crops it can be economically serious. Early and preventative action wins.

When it appears

Warm days, cool nights, high humidity, and dense shaded canopies.

How to identify it

  • White or grey powdery patches, usually on upper leaf surfaces
  • Patches merge until leaves look dusted with flour
  • Yellowing, curling, and early leaf drop

How to manage it

  1. Open the canopy for airflow; avoid excess nitrogen.
  2. Remove affected leaves.
  3. Apply Mildew Control (1:2,000) at first sign and preventatively on susceptible crops.

Recommended Vegalab program

RoleProductUse
Primary controlMildew ControlGeraniol 17%; preventative + early curative
Broad-spectrum companionSpore ControlThymol broad-spectrum fungicide
Plant resilienceArmour BoostSilica for resilient tissue

Product claims, rates, and availability vary by jurisdiction; always follow the applicable label.