First, the incidence of symptoms of seedling stage, mainly damage the leaves. First, a water-stained dot on the back of the leaves, followed by 0.2-0.5 cm yellow-brown or gray-brown round or irregular-shaped necrotic spots on the leaf surface. The edges are darker in color and appear greasy, and some are interconnected into larger ones. Plaques, when the weather is dry, the lesions are brittle and cause dead leaves.
Second, the transmission of pathogenic bacteria in the seeds or sickness of the overwintering, as early as the source of infestation in the early years, in the field by rain and irrigation water and pests spread, the incidence of moderate temperature 25 ~ 27 °C, cabbage enters the period from the rosette to Baoxin period There is continuous rain, which is conducive to the occurrence or prevalence of the disease, and the incidence of dark green leafy cabbage and continuous crops is heavy.
Third, the prevention and treatment method The initial stage of onset of spraying 14% solution ammonia copper water agent 350 times, but the copper sensitive species with caution. In addition, it can spray 72% of agricultural streptomycin sulfate powder 3000 times or neophytin 4000 to 5000 times, every 7-10 days, continuous control 2-3 times.
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