The symptoms are also called verticillium wilt or premature disease. In the early stage of disease, the tip of the leaf turns yellow along the leaf margin, yellowing from the veins, and then turning brown from yellow to dry, but not curly, until all the compound leaves die without falling off. Roots and stems are not obvious at the initial symptoms. When the leaves are yellow, the vascular bundles at the cut open roots have been browned, and the vascular bundles on the stems at the back have become brown. Tuber disease began at the umbilicus, and the vascular bundles turned light brown to brown. The diseased potato showed a "eight" semi-circular discoloration ring. The pathogen Verticillium dahliae Kleb. called Verticillium dahlia, is a fungus of the subphylum Fungi. The mycelium is colorless, old and brown, separated and branched, with a size of 25–21521–69 (μm). The base of conidiophores is always transparent, with 2-4 sprigs on each spore, 13.7-21.42.3-2.7 (μm) in size, and one or more conidia on each sprig. The conidia are oval in shape, and the unit cells are colorless, and the size is 2.3-9.11.5-3.0 (μm), which can form micro sclerotia.
Transmission routes and conditions The disease is a typical soil-borne vascular malaise. The bacteria used micro-sclerotia to overwinter in the soil, sterilized straw and potato chips, and the diseased potato was cultivated in the following year. The bacteria in the body
It spreads, propagates in vascular bundles, and spreads to branches and leaves. The disease is no longer repeated in the year. Germ development temperature 19-24 °C, the highest 30 °C, the lowest 5 °C, mycelium, sclerotia 60 °C after 10 minutes to death. Generally, the temperature is low, and the wound healing of the seed potato blocks is slow, which is conducive to the invasion of pathogens from the wound. From sowing to flowering, the average daily temperature is lower than 15°C for a long time, and the onset is early and heavy; during this period, the climate is warm, the rainwater is harmonized, and the disease is obviously alleviated. Low-lying terrain, application of unfamed organic fertilizer, improper irrigation, and incidence of continuous cropping. In addition, V.albo-atrum Reinke et Berthold has also been reported to cause the disease.
Control methods (1) Breeding disease-resistant varieties such as Alfy, Dixin, Spartan, Berek and other varieties are more resistant to disease. (2) Apply compost or fermented organic fertilizer. (3) Seed potatoes were soaked with 0.2% of 50% carbendazim WP prior to sowing for 1 hour. (4) More than 4 years of rotation with non-solanum crops. (5) Severe disease areas or fields, soil disinfection with 50% carbendazim 2kg per 667m2; spraying 50% carbendazim WP 600-700 times or 50% benomyl WP 1000 Diluent, in addition can be watered 50% citrate copper wettable powder 350 times the liquid, each strain of the irrigation of good liquid 0.51 or 12.5% ​​synergistic carbendazim Solvent 200 to 300 times the liquid, each watering 100ml. Irrigate once or twice every 10 days.
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