In late autumn, over-winter cucumbers are planted in greenhouses one after another. Due to the large temperature difference between day and night and heavy dew, the growth environment is very suitable for downy mildew and powdery mildew. Attention should be paid to prevention and control.
Downy mildew mainly damages the leaves, and the lesions are easily diagnosed because they are polygonal, light brown or brownish due to limitation of veins. Appropriate disease temperature 15 ~ 22 Â°C, relative humidity higher than 83%, when the leaves have water droplets are susceptible to disease. Agricultural control should be kept in the pastoral cleanliness, reasonable dense planting, high ridge cultivation; under the film dark irrigation or drip irrigation, water-saving insulation, in order to help reduce the humidity within the greenhouse; early morning ventilation as soon as possible; balanced application of NPK fertilizer. Before the onset, Dakkonin 75% chlorothalonil WP can be used 600 times, Amisida 25% azoxystrobin 1500 times, Dasheng 80% Mancox Zn WP 500 times, 56% Chlorothalonil suspension solution 800 times liquid spray. Immediately after the emergence of a central diseased plant in the field, a full-scale spraying was performed and the diseased leaves were promptly removed and burned out of the shed. Jin Lei 68% fine arsenic Mn-Zn water dispersible granules 500 to 600 times liquid, Ruifan 25% difonofosfamide suspension 1500 times, silver Fali 68.75% fluorescens propamocarb suspension 800 times Liquid, anti-virus, antimony 64% Mn Zn WP 500 times, Prec 72.2% Promectazole HCl 800 times and other spray control.
Powdery mildew mainly damages the leaves. At the beginning of the disease, white sparse mold layer appeared on the leaf surface. The mold layer gradually thickened to form thick white round spots, which eventually led to yellow leaf necrosis. In severe cases, it infected the stem vines. The pathogens are prone to disease and epidemics under the conditions of warm air, wet weather, rainy weather, and sheltered conditions. Floods are flooded, humidity is high, fertility is insufficient, and plant growth is weak. Prevention and control of agriculture should be given appropriate biological fertilizer, phosphorus and potassium fertilizers, strengthen field management, reduce humidity, enhance air and light transmission. Chemical control: Amisite 25% azoxystrobin suspension 1500 times, Dakkon 75% chlorothalonil wettable powder 600 times, Sego 10% difenoconazole water dispersible granules 2500-3000 Times liquid, Dasheng 80% mancozeb WP wet 600 times, plus 2% of the water, 400 times the solution of kasugamycin, Fuxing 40% fluorosilicon emulsion EC 4000 times spray.
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