How to identify citrus powdery mildew?

Powdery mildew is mainly distributed in citrus producing areas such as southwest and south China. It mainly harms young branches and leaves and young fruits. After citrus was infected with this disease, white mildew spots appeared on both sides of leaves, most of which were nearly round. Mold spots spread outward from the center, forming a white powdery covering on the surface of leaves. The leaf tissue under the moldy layer was initially soaked in water and gradually turned green, forming yellow spots. In severe cases, the diseased spots spread all over the leaves, causing the young leaves to wither and the old leaves to distort. After the leaves are aged, the white mold layer at the diseased part becomes light grayish brown. The diseased part can spread from the leaves to the branches. In severe cases, the leaves shrink and the branches die, and the leaves are often not sticky after drying. The lesions of shoots and young fruits were similar to those on leaves in the early stage, but the host tissues had no obvious spots, and the lesions were contiguous in the later stage. White hyphae spread to the whole branch and young fruit, and the fruit was slightly sour, which lost its edible value and fell off in severe cases.