Tea tree branch black spots

Symptoms occur in Zhejiang, Jiangsu, Anhui, Guangdong, Guangxi, and Guizhou provinces. It is mainly the tea branch of Taiwanese tea. It usually occurs on the red wood shoots that were half-lignified in the year. It has irregular gray-brown irregular patches, and it expands upwards and downwards. The length is 10-20 cm. The branches are all gray and white. The black spots that are slightly shiny from round to oval black are the apical plate of the pathogen.

The pathogen Cenangiμm sp. called a thin disk bacterium belonging to the genus Ascomycota. The small, scattered black spots of the disease are the sub-capsules of the pathogen, sessile, non-subcutaneous, leathery, slightly shiny black, cup-shaped, 0.5 mm in size. The asccus is straight or slightly curved, stick-like, 114 to 17224 (μm) in size, containing 8 ascospores. Ascospores are arranged in double rows in the upper part of the ascus, the lower ones are single or cross arranged, single cells, colorless and transparent, long oval to spindle, some slightly curved, size 22-425.5-7.5 (f4m ). Lateral filaments are produced between the ascostic sac, which is longer than the ascospores and has a size of 66-3633.3-4.4 (74m).

Transmission routes and conditions The pathogens overwinter in the diseased tissue with mycelium and ascaria discs. When the conditions in late spring are suitable, ascospores are produced and transmitted through wind and rain to invade shoots. A new ascus is produced in late March and early April, and in the middle of May and mid-June, it enters a period of high incidence. Temperature of 20-25 °C, relative humidity higher than 80% conducive to the occurrence and expansion of the disease. There is a difference in disease resistance among varieties, and tea varieties that germinate early are susceptible to disease.

Prevention methods (1) Selection of disease-resistant varieties such as Taiwan Tea No.12; (2) Cutting off diseased shoots in time and carrying them to the tea plantation and burning them out. Severe disease should be re-cut, which can effectively reduce the initial infection source and reduce the incidence. (3) Timely spraying of 50% benomyl WP 1500 times or 25% carbendazim WP 500 times, 70% thiophanate-methyl (thiophanate-methyl) WP 900- 1000 times liquid. Prevention 1 to 2 times.

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