Teachers, what is the disease of this melon? The picture has been uploaded, thank you.

Melon downy mildew, onset temperature 15 ~ 22 degrees, humidity above 80%. It is easy to happen when there are water drops on the leaves, and a gray-black mold layer can be produced on the back of the leaves with small yellow spots. Melon downy mildew, the onset temperature is 15 ~ 22 degrees, the humidity is above 80%, and it is easy to occur when there are water droplets on the leaves, and gray-black mold can be produced on the back of the leaves with small macula. Add 64% frost zinc, 69% manganese zinc, alkenyl, 60% fluorine, manganese zinc, 72% frost urea, manganese zinc and kasugamycin for control. The above drugs are used alternately, once every 5 ~ 7 days, and silica gel adjuvant is effective.