Downy mildew is one of the important diseases of cucumber. It has the characteristics of rapid spread, short incubation period, fierce and serious damage. Under suitable temperature and humidity conditions, the disease spreads very rapidly, especially in the rainy days and humidity. In large time, a large number of leaves can die in 3-5 days, and the disease is easy to occur in open fields and protected areas, usually reducing production by 20%-30%, and even causing no harvest, should be highly valued, early prevention and early treatment.
Symptoms identified chlorosis on the cotyledon of the seedling stage, gradually showing irregular spots of yellowish yellow. When wet, the gray-black mold layer was formed on the back of the leaves, and the cotyledons quickly turned yellow and dry.
The water-soaked spots appeared on the leaves of the susceptible period in adult plants. When expanded, they were restricted by the veins and showed a polygonal shape. The lesions gradually turned yellowish or yellow, and finally became pale brown. The edge of the lesion is obvious, and the late lesions merge into a piece. Under the wet condition, the surface of the leaf produces a pale purple to gray black mold layer.
Generally, the lower leaves of the plant spread to the upper part of the blade. When the disease is serious, multiple lesions are connected into pieces, and the whole leaves become yellow-brown, dry and contracted and die.
Control technology 1, selection of disease-resistant varieties, rational fertilizer management: selection of Jinyan series, Jinza 1, 2, Baoyang 5, Zhongnong 1, 3, Xi Nong 58, Guangzhou Quanqing and other disease-resistant cucumber varieties; The organic fertilizer, the application of phosphorus and potassium fertilizer, sprayed potassium dihydrogen phosphate, borax, urea mixed solution, spray once every 10 days, even spray 2-3 times, can quickly provide nutrition to the plant, improve plant disease resistance, The number of waterings should be properly controlled during the early growth period.
2, ecological disease prevention: the use of cucumber and downy mildew on the requirements of different growth environment conditions, the use of methods that are conducive to the growth of cucumber and inhibit downy mildew to achieve disease prevention purposes. The method is as follows: after sunrise, the shed temperature is controlled at 25-30 °C, the relative humidity of the ventilation is reduced to 60-70%, the afternoon temperature is lowered to 20-25 °C, and the relative humidity is reduced to about 70%. When the minimum temperature reaches 12 °C at night, it can be vented all night.
3, high temperature shack sterilization, in the sunny day at noon shack for 2 hours, so that the temperature near the plant growth point reached 45 ° C, and then wind and cool. Once in 7-10 days, watering the night before the shack increases the humidity in the shed.
4. Chemical control:
Pre-injury prevention, 77% can kill WP 1000 times solution, 75% chlorothalonil WP 600 times solution, Dasheng M-45 WP 800 times solution, 56% yam WP 600 times solution Spray, pay attention to alternate use, such as 72% DuPont dew WP can be safely separated for 10 days, 72.2% Plex water-soluble liquid safety interval is 8 days, 77% can kill WP safe interval For 6 days, the safety interval of 47% Garonne WP was 10 days. Within 7 days of the initial onset, pay attention to timely spray control. Choose 58% nail cream, zinc WP 600 times solution, 72% DuPont condensate WP 800 times solution, 69% Anke zinc WP 1000 times solution. 52.5% anti-purifying water-dispersible granules 3000 times liquid, 72.2% Plex water-soluble liquid 800 times liquid, 47% ruinong wettable powder 800 times liquid, 64% anti-virus hydrating powder 1000 times liquid, 30% The enoylmorpholine wettable powder 1000 times liquid or the like is sprayed. 72.2% fungicide may also be sprayed propamocarb 60-100 ml / acre, spraying diluted 500-800 times, security products on Cucumber interval of three days, 3-4 times for spraying crops quarterly should. On rainy days, you can use smoked or dusted with 45% chlorothalonil fuming agent 200-250 grams or 5% chlorothalonil dust or 5% garnin dust.
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