How to Organically Control Powdery Mildew

In this video, Tricia shares her tips on controlling powdery mildew, organically!

How to Prevent and Treat Powdery Mildew Organically

Powdery mildew can be a persistent and frustrating issue for gardeners, affecting a wide variety of plants, from roses to vegetables and even grapevines. Here’s how to identify, prevent, and treat powdery mildew organically.

Understanding Powdery Mildew

Powdery mildew thrives in Mediterranean climates with temperatures between 65°F and 80°F and high relative humidity. It appears as white, powdery spots on leaves, stems, and fruit. If left untreated, it can stunt plant growth and reduce yield.

Prevention Starts with Healthy Plants

Start with resistant varieties where available. Match sunlight, spacing and care to the plant, and avoid overcrowding.

Improve air circulation with suitable spacing, staking or pruning. Check new growth regularly so you can identify symptoms early.

Organic Fungicides and Treatments

If prevention isn’t enough, organic fungicides and oils can help:

• Sulfur: Effective as a preventive treatment but should not be applied to sulfur-sensitive plants like apricots.
• Serenade: A biological fungicide containing beneficial bacteria to attack the mildew fungus.
• Horticultural Oils: Neem oil and similar oils can treat and prevent mildew but must not be used within two weeks of sulfur applications; some labels require a longer interval. Follow label temperature, plant-sensitivity and application precautions.

Identify and Act Quickly

Using pest ID cards can help you confirm the presence of powdery mildew and other plant diseases. Early intervention is key to preventing the spread of this common problem.

Choose treatments only after confirming the disease. Follow the current label for the plant, application rate and precautions.

Compare our powdery mildew products by labeled crop and use. Check each product’s current organic-use status rather than assuming all products in the collection qualify.

Reference: UC IPM’s powdery mildew guidance.