Powdery Mildew

This disease is caused by a fungus that overwinters in leaf bud scales. In mid-spring and summer, the leaves, shoots, and flowers are covered with whitish, chalk dust-like masses of fungal strands and spores. Infected leaves and flowers become distorted and do not fully expand. Wind spreads the fungal spores to other plants. Many different kinds of ornamentals are susceptible to this disease.

Control: Plant resistant cultivars. Prune out and discard light infestations. Avoid crowding of plants to reduce humidity levels. Fungicides are available.