Downy mildew The most common disease in spinach cultivation areas in the south is downy mildew. The disease is caused by a fungus called spinach downy mildew. The symptoms of field hazards are: the main damage to the front of the blade, the lesion is light yellow, irregular shape, size, diameter 3-17 mm, the edge is not obvious. After the lesions are enlarged, they are connected to each other and become brown in later stages. A grayish purple mold layer develops on the lesion on the back of the leaf. The disease gradually developed from the outer leaves to the inner leaves and expanded upward from the lower part of the plants. During the drought, the diseased leaves were yellow, and when the humidity was high, they were rotted. The severe leaves of the entire plant turned yellow and died. At a temperature of 10 degrees Celsius and a relative humidity of 85%, the planting density is high, water accumulation and sowing are too early and the disease is severe. Since the downy mildew of spinach is overwintering in overwintering vegetable strains, seeds or in diseased leaves, late springs spread under wind, rain, agricultural implements, insects and agricultural operations under suitable environmental conditions, and the pathogens invade through the host epidermis or stomata. Therefore, prevention and treatment of spinach downy mildew should take the following measures: 1, to strengthen the cultivation and management. Rational close planting, scientific irrigation, reduce the humidity in the field; 2, select resistant varieties. Savo hybrids No. 612, No. 621, Barnti, Bowners, and Doetet, etc., can be used, and sharp-leaf varieties can also be used. 3. Seed-cultivation in disease-free or disease-free plants. Such as seed fungus can be used before sowing with 50% thiram seed dressing, the amount of the seed weight of 0.4%; 4, early in the spinach field found diseased plants, to be promptly removed, brought out of the field burned down; 5, In the initial stage of onset, spray 40% EB aluminum wettable powder 200-250 times, 58% metalaxyl, spray 40% EB aluminum wettable powder 200-250 times, 58% metalaxyl manganese zinc wettability 500 times liquid powder, 64% anti-virus WP 500 times, or 72.2% Prec fluid 800 times, spray once every 7-10 days, continuous 2-3 times. Fusarium wilt spinach wilt generally occurs in the adult stage. The performance of the old leaves darkens and loses luster. The mesophyll gradually yellows and gradually expands upwards. When the downward development progresses, the roots turn brown and die. Early onset plants were significantly dwarfed. When the weather is dry and the temperature is high, the diseased plants quickly become chlorotic. In damp, low-temperature conditions, diseased plants can continue to survive for a period of time, sometimes producing new lateral roots. However, in the event of hot weather, it quickly died. Fusarium oxysporum f. sp. tritici mainly grows in the soil or on the seeds with the diseased plants in the soil or overwinters. The seeds can be borne, and the unfermented manure can also be carried. Germs can spread with rainwater and irrigation water and invade directly from the wound or apex of the root, and can reach the vascular bundle after invading. In vascular bundles, germs produce toxic substances that block the catheter and cause the leaves to dying. High temperature and humidity are conducive to disease; soil temperature is around 30 degrees Celsius, soil moisture, fertilizer is not fully decomposed, many underground pests, nematodes are more susceptible to disease. Control methods: 1. Perform 3-5-year rotation with onion-type and grass crops to avoid continuous cropping; 2. Apply compost or fully mature organic manure made by Japanese enzyme bacteria and adopt formula fertilization techniques to improve host disease resistance Force; 3, the use of sorghum or ridge cultivation, timely drainage after the rain, is strictly prohibited flood irrigation; 4, found that the central diseased plants in a timely manner, disease points and around 50% benomyl WP wet 1500 times, 40% Polysulfide suspension 500 times liquid, or 10% Zhiwei Ling Shui agent 300-400 times liquid, spray once every other half a month, 2-3 times in a row. White spot disease The symptoms of spinach leukoplakia mainly manifest on the leaves. The lower leaves began to develop. The lesions were round to near-circular, and the edges of the lesions were obvious. The size was 0.5-3.5 mm. The lesions were yellow-white in the middle, and the outer edges were brownish to purple-brown. They gradually developed into white patches. When the humidity is high, some gray spots appear on the lesions. When the wet and dry transition is intense, the lesions are easily broken in the middle. The appearance of this symptom is caused by the infestation of Cercospora hepatica. In addition to harming spinach, this fungus also harms sugar beet and other plants and causes similar symptoms. White spinach spinach fungus grows with mycelia in the soil with the diseased body, and the Hunchun spring spleen spreads through wind and rain. Weak growth, warm and humid conditions, easy to disease, low-lying terrain, nest wind, poor management and disease severity. Control methods: 1. Choose spinach with a flat topography and sufficient organic manure to plant spinach, properly water it, manage it carefully, and increase the resistance of the plant; 2. Dispose of the diseased body promptly after harvest to concentrate it deeply or burn it in order to reduce Source of disease; 3, in the initial stage of disease, spraying 30% of green suspension suspension 400-500 times, or 1:0.5:160 times the amount of Bordeaux mixture, 75% chlorothalonil wettable powder 700 times, 50% of the mold Ling wettable powder 1000-1500 times, spray once every 7-10 days, continuous 2-3 times.
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