What symptom is characteristic of powdery mildew infection?

A characteristic symptom of powdery mildew infection is the presence of white powdery spots on the leaves and stems of affected plants. This fungal disease typically appears as a white, talcum powder-like coating that can cover the upper surfaces of leaves, as well as flowers and stems. The powdery appearance is due to the growth of the fungus, which thrives in warm, dry conditions, making it easily recognizable.

This differing symptom from other plant issues is key in diagnosing powdery mildew. For instance, dark spots on leaves are more often associated with different types of fungal diseases or leaf spots. Curling leaves can indicate various stressors such as insect damage or environmental factors, and sticky residue is typically a sign of pests like aphids or whiteflies feeding on plant sap. Thus, the distinct white powdery appearance is the definitive symptom that identifies powdery mildew.