- Powdery mildew usually begins with small whitish round spots on a plant's leaves. These spots will quickly grow, covering the entire leaf when conditions are right. Powdery mildew normally appears late in the growing season when temperatures cool and humidity is high. Powdery mildew will deform leaves and buds, cause substantial leaf drop, take the nutrients from the plant, and shorten the plant's growing cycle. Some plants will prematurely die from powdery mildew infection.
- Powdery mildew does not like full sun or high heat. If at all possible, locate your plants where they will receive sun, particularly in the morning, which will dry the dew off the leaves. If you have plants growing in shaded areas, keep them well spaced since crowded plants will raise the humidity level which invites powdery mildew. There are plants that are more resistant to powdery mildew, so if those can fit into your landscape needs, select them.
- Forgo watering in the evening or over night and instead water in the early morning so the plants and ground will be dried by the morning heat. As the temperatures cool toward the end of the growing season, cut back on the amount you water and how often.
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In shaded areas, use a fertilizer that has a lower nitrogen level because powdery mildew loves nitrogen and will be more attracted to a higher nitrogen environment.
If you notice a few leaves, buds or stems infected, prune them off your plant and immediately discard. Be sure to thoroughly clean any pruners or other tools you use after they have been in contact with powdery mildew to avoid the potential of spreading the disease to healthy plants.
Powdery mildew can live on the dead leaves around a plant so remove debris from around the plants and dispose of it.
