Grape brown spot occurs in various grape producing areas in China. It is affected by rainy and humid coastal areas and various provinces in the south of the Yangtze River. The incidence is generally lighter in dry regions or less rainy years. Poorly managed orchards in the late years of the rainy season can cause a large number of diseases and cause early defoliation. , affecting tree vigor caused by reduced production.
? Disease? Brown spot is caused by the infection of Pseudomonas crustacea. It mainly damages the leaves. The spot of infection is light brown and irregular keratinous spots at the beginning of the disease. The lesions gradually expand and the diameter can reach 1 cm. The spots turn brownish brown, and then turn auburn brown, with yellowish-green spots on the periphery. In severe cases, the spots are linked to large spots with clear edges. The back of the leaves is ambiguous, and the diseased part is dead in the later period. When the rain is heavy or the humidity is high, brownish-brown moldy matter occurs. Some lesions have inconspicuous bands.
Infestation and onset of disease? Conidia of brown spot pathogens have a long life span, can adhere to overwintering on the surface of shoots, spread by wind and rain, germinate under conditions of high humidity, and infiltrate from the stomata on the back of the leaf. The incubation period is about 20 days. In the northern part of the country, the onset began in June, and in July-September, it was repeated infestation in the most prolific rainy season, resulting in a major outbreak. There are two peaks in Jiangsu, Zhejiang, and Shanghai, the first in June and the second in August.
1. Completely remove litter to reduce the source of disease. Spray 3 to 5 degrees lime sulfur before germination.
2, spraying control. Severely affected areas combined with other disease prevention and control, in June can be sprayed an equal amount of 200 times Bordeaux mixture, from July to September can be sprayed 500 times 50% carbendazim, 600-800 times chlorothalonil or 800-1000 times 70% thiophanate used alternately and sprayed once every 10-15 days. 65% of mancozeb has phytotoxicity on certain grape fruits, more obvious in the north, and the use concentration should be 1000-1200 times.
3, rational fertilization, scientific pruning. Increase the use of multi-element compound fertilizers. Strengthen the tree vigor, leave the branches high in resistance to disease, timely pruning and pruning, ventilation and light.
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