Powdery mildew of Strawberry
The first symptom seen is usually the curling up of leaf margins, exposing the white patches of mycelium on the lower leaf surface. The patches may eventually coalesce to cover the entire underside of the leaf. Magnification may be required to see this, as powdery mildew on strawberry leaves is not as obvious as on other plants. Infected leaves may curl and purple and reddish blotches can also appear on the lower leaf surface, and numerous black specks (cleistothecia; also called chasmothecia) may be observed. Flowers, petioles, and fruit also can become infected. Economic loss may result from fruit infection. Infected berries will have a dull sheen and mycelium is visible using a 20 to 30x hand lens. In severe cases, fruit may become cracked and have a tan to rusty-pink appearance. Heavy powdery mildew infection may result in a serious reduction in photosynthesis, affecting overall plant vigor, fruit production, and quality.