Powdery mildew

A fungus that grows as white, flour-like patches on leaves. It loves stagnant, humid air and soft growth, so fix airflow early and catch it while patches are small.

Symptoms

• Small round white, powdery spots on leaves, often starting on older or shaded leaves.
• Spots spread and join into a flour-like coating; the powder rubs off.
• Leaves yellow, then brown and dry, and vigour drops.

Quick checks

• Check humidity against the chart for your week, day and night.
• Feel for still air pockets inside the canopy.
• Look at the oldest and most shaded leaves first.
• Is the plant overfed?

How to fix it

1. 1
   Environment

   Lower humidity and get air moving

   Bring humidity into your week's range, increase extraction, add gentle clip-fan movement through the canopy and keep night temperatures within about 5–8 °C of the daytime figure.

2. 2
   Physical

   Remove infected leaves straight away

   Carefully remove affected leaves, bag them inside the tent and take them out. Thin the canopy and space plants so leaves don't overlap.

3. 3
   Safe treatment

   Only a UK amateur-approved treatment, early only

   If you need more than environment and hygiene, use a product approved for amateur use in the UK that lists powdery mildew on its label, only in the growth stage or very early flower. Never on maturing flowers.

4. 4
   Support

   Strengthen the plant

   Keep Stress in the feed every week. Silicon is known to strengthen cell walls and can help resistance to mildew, but it won't clear an existing infection.

Likely causes

• Humid, stagnant air with poor airflow through the canopy.
• Plants packed too densely with a crowded canopy.
• Big day-night temperature swings.
• Soft, lush growth from too much nitrogen.
• Intermittent drought stress.
• Spores brought in on other plants or carried over from a previous run.

What to avoid

• Don't spray anything onto developing or maturing flowers.
• Don't foliar spray (including Monkey Mist) onto infected plants in a humid tent: wet leaves in still air favour other diseases.
• Don't overfeed nitrogen.
• Don't brush infected leaves against healthy ones.

Prevention

• Keep humidity in the chart range and air moving through the canopy.
• Give plants space.
• Feed to the chart, and avoid swinging between bone dry and soaked.
• Clean the tent thoroughly between runs.

Monkey products that can help

Stress

Silicon is known to strengthen cell walls and can help the plant resist mildew and other stresses. Not a cure.

2 ml per 10 L every week. Always add it to the water first and mix thoroughly before adding anything else.

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Products support a healthy plant. They don't replace fixing the cause.

When to get help

If mildew reaches the flowers, or keeps spreading after you've corrected humidity and airflow, email info@monkeynutrients.co.uk with photos.

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