How do I fix powdery mildew on cannabis?

A common fungal disease recognized by white powdery spots on leaves and stems. It reduces photosynthesis and weakens the plant, thriving in warm, dry conditions with poor air circulation. Remove and destroy heavily infected leaves. Spray a milk-water solution (1:9) or potassium bicarbonate as an organic remedy. Improve airflow and reduce humidity around plants.

Visual Guide

Powdery Mildew.

Remove and destroy heavily infected leaves

← All problems

White, powdery spots on the upper side of leaves

Photo

Mould & mildew

A common fungal disease recognized by white powdery spots on leaves and stems. It reduces photosynthesis and weakens the plant, thriving in warm, dry conditions with poor air circulation.

Looks like this

White, powdery spots on the upper side of leaves
Yellowing and curling of affected leaves
Reduced vigour and slowed growth

Solve it with Vitaponix

Our nutrients don't kill pests or mould — they keep plants strong while you follow the fix below.

VitaSilica →

High-quality silica with added potassium, 1 ml/L from week 2. Supports sturdier plants.

VitaCal →

Increases calcium absorption to strengthen plant cell walls. 1 ml/L, weeks 3–8.

How to fix it

Remove and destroy heavily infected leaves
Spray a milk-water solution (1:9) or potassium bicarbonate as an organic remedy
Improve airflow and reduce humidity around plants

Why it happens

High humidity with stagnant air
Large temperature swings between day and night
Overcrowded plants and poor airflow

Prevent it

Space plants properly and prune for airflow
Follow the official feeding chart humidity targets for each growth stage
Maintain steady temperatures with minimal night drops

Doses and targets come from the official Vitaponix feeding chart. Vitaponix nutrients are plant nutrition, not pesticides or fungicides.

Prevent it next time

Get the full 10-week feeding schedule.

Open the feeding chart Shop Vitaponix →