Introduction to the symptoms of grape downy mildew

Symptom identification: a fungal disease, mainly harmful leaves, shoots and young fruits. The damaged parts of leaves first produce pale chloasma water-soaked spots with unclear edges, and the spots gradually expand into irregular or slightly circular chloasma large spots with diameters up to 1~3 cm. The edges of the spots are unclear, and multiple spots can be connected to form large spots. The back of the spots with high humidity produces gray white, like frost mold layer. In dry years, the frost mold layer is not produced when the atmospheric humidity is low. Disease spots into reddish-brown or yellow brown, severe disease spots and disease spots outside the leaves dry or dry leaves, and lead to shedding. The damaged part of the new shoots produces water-soaked brown spots. When it is serious, the new shoots are distorted, stop growing or even die. When the humidity is high, frost mold layer is produced on the spots. Tendrils, petioles and rachis can also be killed. The young fruit was damaged and produced water-soaked light brown spots. When the humidity was high, the young fruit and ear produced gray mold layer, and the secondary fruit was seriously damaged in autumn. The fruit is less damaged after coloring.