Powdery Mildew Remedies for Plants | Old Farmer's Almanac
Signs of Powdery Mildew. It starts as white patches on the leaves of squash, lilacs, phlox, bee balm, and other plants, making them look like they have been dusted with baby powder. Early on it wipes off or washes away only to return again. Eventually the affected leaves turn yellow and die on many plants while others continue to soldier on.