Symptoms Jiangsu, Zhejiang, Anhui, Hunan, Sichuan, Guangdong, Taiwan, Yunnan, and Guizhou provinces all have tea regions. The main damage leaves, starting from the edge of the leaves are brown spots, after the expansion of a round or semi-circular to irregular purple brown to dark brown lesions, on the gray-brown small particles, sick and healthy part of the sector is not obvious , but lesions purple black edge (different from Chayuan disease). Sometimes multiple lesions on the leaf margin fuse together, which resembles freezing injury. When the humidity is high, a gray mold layer is formed on the lesion, ie, the conidiophore and conidia of the pathogen. It can be distinguished from freezing injury.
The pathogen Cercospora sp. is a kind of Chaisporium genus, which belongs to the same species as the pathogen of Chayuan brown spot disease. The mold spots on the lesions are pathogenic fungi and conidiophores. The sub-balloon is spherical to nearly spherical, with a diameter of 40-100um. The conidiophore plexus grows on the sub-epidermis, with a single conidial stem, straight or slightly curved, with a size of 12-752-3 (um). Conidia whip, base basally, tip tapering, colorless to light gray, size 40-923-5 (um), separated by 4-10, spores mature after separation.
Transmission routes and pathogenic conditions The germs use mycelium blocks (mycelium or sub-seats) to pass through the diseased leaves of diseased trees and diseased fallen leaves on the surface of the soil. If the conditions in late spring are appropriate, the diseased part will produce conidia, which will cause wind and rain. After spreading, the disease began to develop after about 5 days of invading the leaves. After repeated infections, the disease spread continuously. The disease is a low temperature and high humidity type disease. Every year in the early spring and late autumn, from March to May and from September to November, most occur. Anhui has more occurrences in autumn than in spring. Suffering from frost damage, lack of fertilizer, or excessive picking, tea trees are vulnerable to disease. Tea gardens have poor drainage and heavy moisture retention. There are differences in disease resistance among varieties.
Control methods (1) selection of disease-resistant varieties. (2) Advocate the application of enzyme composted compost and increase organic manure; strengthen tea garden management, achieve reasonable picking, and adopt combination of picking and brewing; do clean ditch and drainage work, drain water in time after rain, and prevent moisture from staying; Cold work to prevent frost damage to reduce the incidence. (3) Spray 70% thiophanate-methyl wettable powder 1000 times or 50% benomyl WP 1500 times, 75% chlorothalonil wettable powder 700 times in the spring before picking, or early spring or late autumn. . It can also be used 0.6% to 0.7% lime half Bordeaux liquid or 12% green milk copper EC 600 times.
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