Sweet potato black shank disease

The symptoms are also called sweet potato black spot. Growth period or storage period can occur, the main infringement of potato seedlings, potato blocks, does not harm the green parts. The white part of the stem base of infected potato seedlings produces a black sub-circular slightly concave spot, the latter stem rots, the plant withers, and the diseased part has a moldy layer. The tubers showed black small round spots at the beginning of the disease. After expansion, the black and green sickles with irregular outlines were slightly darkened. The diseased pods were grayish mouldy, with black bristles, and the diseased potato had bitter taste. The storage period could be Continue to spread, causing a rotten cellar.

The pathogen Ceratocystis fimbriata E11is.et Halsted called long-shelled fungus of sweet potato belonging to the fungus Ascomycotina. Asthenocytic shells that are sexually produced are found in the center of the lesion. The asccus shell is spherical at the base, with a longitudinally-striped long-necked neck, an endogenous pear-shaped ascospores, and eight ascospores in each acanthus. The ascospore cells are colorless and have a thin wall with a helmet-like shape and a size of 4.5-7.83.5-4.7 (μm). The ascospores have a short life span, but play an important role in the epidemic of the disease during storage. The hyphae are colorless and transparent at the beginning, and become dark brown after being matured, with a width of 3 to 5 μm, and are parasitized in host cells or intercellular spaces. The asexual state produces conidia and chlamydospores. Conidia are produced by spores on the tip or side of the mycelium. The conidia unit cells are colorless, cylindrical to stick-like or dumbbell-shaped, with multiple ends truncated at a size of 9.3–50.62.8–5.6 (μm). Immediately after the spores have formed, they germinate and sometimes produce a series of conidia after germination. This produces sclerotia after 2-3 generations. Some also form chlamydospores after germination. The chlamydospores are dark brown, elliptic, with thick membranes, sizes 10.3 to 18.96.7 to 10.3 (μm).

Transmission routes and pathogenic conditions The pathogens use the chlamydospores or ascospores to overwinter in the soil in storage pits or seedbeds and fields, and some are attached to seed potatoes with mycelium or lurk in the t And the initial infection source of the third year. The bacteria can directly invade the seedling roots, but also

Invasion from wounds, lenticels, and roots on the tuber, and frequent infection after onset. Low-lying terrain, heavily soiled soils, or rainy years are susceptible to epidemics, with high cellar temperatures, high humidity, and heavy onset when ventilation is poor.

Control methods (1) Set up a disease-free farmland, carefully select the seed potatoes in the pit, and prevent the spread of diseased potatoes. (2) Seed potatoes were soaked with 50% carbendazim wettable powder 1000 times for 5 minutes. (3) After high-cutting of the potato seedlings, use 50% thiophanate-methyl WP to dip the seedlings for 1500 times for 10 minutes, and require the liquid to be immersed in the rattan l/3 at l/2. (4) Selection of resistant varieties such as Jinshu 6, Eshu 2, Xiangshu 15, 190 sweet potato, Lushu 2, Lushu 3, Lushu 7, Beijing 553, Jishu 10, etc. .

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