Protecting Tomatoes from Powdery Mildew

There are hundreds of types of powdery mildew. If you use sulfur dust on your tomatoes, you won't have much of a powdery mildew problem. Without it, you will get powdery mildew at some point.

What It Looks Like

Powdery mildew is a fungus living on leaves. It spreads to nearby leaves and plants. The fungus spores are in the air and attach themselves more easily to moisture on leaves.

The Solution: Sulfur Dust

Sulfur dust is an organic way to protect your plants against powdery mildew. It prevents spores from reproducing.

Use sulfur dust, not sulfur powder. There's a difference in effectiveness.

When to apply: Apply sulfur dust when you first see powdery mildew. It should stop the spread to other leaves.

Read our complete sulfur dust application guide →

Why It Matters

Usually you get your crop of tomatoes before mildew takes the plant. But remember—leaves are the food factories of the tomato plant. When diseased, this stresses the plant, just like disease would stress you.

Prevention Tips

Water in the mornings so plants and leaves have all day to dry and water can evaporate.

Watch sprinklers - Be careful of sprinklers coming on at night. Overspray and mist getting leaves wet invites mildew.

Space plants properly - Leave room between plants for better air circulation. Keep plants from touching each other and spreading mildew.

Consider sunlight - Mildew likes cooler, shady areas. Direct sunlight kills or slows growth.

Know your varieties - Some varieties get powdery mildew more than others.

Once You Have It

Apply sulfur dust to stop the spread and address the issues above. The combination of sulfur dust and better cultural practices will keep it under control.

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Next Steps

Learn how to apply sulfur dust →
Master proper watering timing →
Review the fundamentals →

Dave Freed / The Tomato Guy