The false black spot of rapeseed and small rapeseed is mainly harmful to leaves. In severe cases, the lesions merge with each other, causing the leaves to dry up, and the disease sometimes occurs in combination with black spot. Timely pesticide control is necessary. The China Pesticide Network Xiaobian introduces you to specific prevention methods.
The pathogen Alternariaalternata (Fries) Keissl. Synonym, A.tenuisNees formerly known as Alternaria, the latter is called Alternaria, is a fungus. Conidiophores clustered, dark brown, shortly thick or irregularly stick-shaped, with 2 to 9 septums, 27 to 110 × 2.75 to 4.5 μm in size, with conidia at the apex. Conidia inverted bar or cylindrical, pale yellow, size 9.5 ~ 40 × 5 ~ 11.25 microns, with 1 to 6 mediastinum, most 3 ~ 4; 1 ~ 5, more than 3, short喙, only half of the length of the spore, more than one sputum, a few 1 to 2 septa, colorless. The vegetative hyphae of this bacterium is mononuclear, individual dinuclear or 3-nuclear, but the cells at the tip of the new hyphae are often multinucleated and concentrated at the top of the cell; the conidia cells are mostly mononuclear, but the spores are the widest There are often 2 to 3 nuclei, mycelium forms collaterals, and when vegetative hyphae form spore stalks or spore stalk spores, the daughter cells grow out of the daughter cells first, and one nucleus of the mother cells or the daughter nucleus of the nucleus migrates. The nascent cells will continue to divide into collaterals, conidiophores and conidia by this nucleus; when the conidia germinate, the germ tubes grow out of the cells, and only one cell nucleus per cell moves into the germination tube, and the germination tube cells Nuclear or dual core. In the past, the bacteria was considered to be saprophytic bacteria, but under suitable conditions, some weak parasitic saprophytic bacteria multiply and cause damage to the host, and the saprophytic bacteria also become pathogenic bacteria.
Routes of transmission and pathogenesis: The pathogens are inoculated with mycelium or conidia on the seedlings, seed surface, diseased bodies or in the soil. Overwintering or over-summering in the soil, becoming the source of infection at the beginning of the year, conidia by airflow Spread and spread, and form re-infection, so that the disease spreads again and again. According to the pesticide network , the bacteria can grow and develop at 10 to 35 ° C, but it often prefers lower temperatures. The optimum temperature is 17 ° C, and the optimum pH is pH 6.6. The pathogen survives in water for 1 month, can survive for 3 months in the soil, and survives for 1 year on the soil surface. Generally, it occurs in the middle and late stages of rape growth or in the off-season cultivation, and the disease is prone to occur and prevalence. In recent years, it has become increasingly serious and has become an important disease in rapeseed production.
Control method:
(1) Large-scale rotation, timely turning the land to clean the pasture after harvest, reducing the source of bacteria in the field.
(2) Apply compost made by Japanese enzyme bacteria or use manure compost to cultivate antagonistic bacteria, strengthen field management, and improve disease resistance and disease resistance of rapeseed.
(3) Selection of resistant varieties such as Qinbai No. 2, Yuyou No. 3, No. 6 (Zhengbai No. 4), Xiaoyeqing rapeseed, and Rongbai No.4.
(4) Seed disinfection, seed dressing can be carried out with 50% of the seed weight of 0.4% of chlorhexidine WP or 75% of chlorothalonil WP. (5) Spraying 64% antivirus WP WP 500 times or 40% chlorothalonil suspension 500 times solution, 70% mancozeb WP 500 times solution, 58% metalaxyl MnZn before spraying. Wet powder 500 times solution, 80% spray WP 600 times solution, 50% phlegm hygroscopic powder or 1000 times solution of its compounding agent.
When black spot disease and downy mildew are mixed, it is recommended to use 70% ethyl phosphine•manganese zinc wettable powder 500 times solution or 60% succinylphosphine aluminum (DTM) wettable powder 500 times solution, 72% frost urea manganese. Zinc (ke anti-linguistic) wettable powder 800 times liquid, or 69% Anke manganese zinc wettable powder 1000 times liquid, spray 660 liters of good liquid per 667 m2, once every 7 to 10 days, continuous control 3 ~4 times. Stop spraying pesticides 7 days before harvesting.
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