Powdery mildew
A white, dusty fungus on leaves and shoots that thrives in still, shady air.
What you'll see
- White to gray powdery patches on leaves, shoots, buds or flowers.
- Twisted, stunted or puckered new growth.
- Affected leaves turn yellow or brown and drop early.
Why it happens
Powdery mildews are fungi that live on the plant's surface. Each kind attacks only related plants, and unlike most fungi they don't need wet leaves.
How to fix it
- Remove the worst leaves and shoots early and bin them.
- Give the plant more sun and space so air moves around it.
- For mild cases, spray horticultural oil or sulfur, but never both within 2 weeks of each other or above 90°F (32°C).
- Use any spray exactly as the label says, and keep kids and pets away until it dries.
Keep it from coming back
- Grow resistant varieties, and give plants sun and room for air to move.
- Feed lightly, since soft growth is more easily infected.
- Water regularly at the roots; thirsty plants are more prone.
Sources
General guidance, not a diagnosis. For valuable, edible or outdoor crops, check with a local extension service or plant expert. Use any product exactly as its label says, and keep children and pets away while it dries.