What is the white fungus growing in my garden?

The white fungus found on leaves in the garden is called powdery mildew. The white splotches are common to all plants, but crab apples, lilacs, roses, grapes, squash and cucumbers are the most susceptible to powdery mildew. Powdery mildew is not fatal to a plant.

Powdery mildew appears in environments that are damp or humid. It also runs rampant in crowded plantings or in areas with poor air circulation. Watering a plant from above also contributes greatly to powdery mildew. Once a plant is infected, all plant parts infected with powdery mildew should be removed. Fungicide should be applied every 7 to 14 days.