Defoliation is often the cause of these diseases:
Leaf blight. The disease is characterized by the largest development from the bottom up, lesions gray, there are perforations in the middle, the late onset of a shake at the bottom of the stem by hand, the leaves“Fluttering” fall, into“Bare rod commander. It is recommended to spray 10% difenoconazole 1500 × solution + 20% Thiram copper 600 × solution, or 20% crown green (prochloraz + Cupric pinonate)800 × solution.
Bacterial leaf spot disease. It mainly occurs in the upper leaves. At the early stage of disease, the leaves appear yellow-green water-soaked dots, and at the later stage, the lesions become rust-colored, and become thin and brittle because of losing the mesophyll and leaving the epidermis. The disease develops rapidly in high temperature and high humidity environment, and leaves fall seriously in the late stage. The control was carried out by spraying 2% kasugamycin (600 ×) + 72% streptomycin (4000 ×) , or 20% yekuzol (1000 ×) , or 33.5% net nut extract (quinoline copper)(750 ×) .
Powdery mildew. White pink spots appeared on the leaves when the disease occurred, and later developed into large pink spots, which covered the whole leaves and caused serious defoliation of the plants. The disease can be prevented and controlled by spraying 25% 1000-fold solution of pyraclostrobin or 30% 1000-1500-fold solution of artesunate.
White Star Disease. The main point of the disease is that the lesions on the leaves are nearly circular, white dots, looking like scattered white stars, causing a large number of defoliation in the late stage. The disease can be controlled by spraying 12% cupric pinoleate emulsifiable concentrate 500 times or 14% cupric amine 300 times.