Powdery Mildew is a fungal disease that can infect many plants in both wet and dry conditions, but is most common in cool, dry weather with high humidity. Powdery Mildew spores require dry conditions to spread and are suppressed by abundant moisture.
Powdery Mildew is easily identified by the white or gray "powder" of spores and fungal strands that form on the outside of leaves (especially new growth), unopened flower buds and sometimes fruit. Left untreated, it can deform and even kill plants. Powdery Mildew is easily spread by the wind and particularly common on plants grown in too much shade, especially roses and vegetables
- If available, plant Powdery Mildew resistant varieties, especially of roses, vegetables and crepe myrtle (usually varieties named after native American tribes).
- Plant sun-loving plants in full sun.
- Prune to keep the plant open for good air circulation.
- Avoid over fertilizing, which promotes succulent growth favored by Powdery Mildew.
- Some rose growers use overhead watering to suppress Powdery Mildew. However, in many climates, this will promote other diseases, including Black Spot.