Cucumber downy mildew, also known as "running horse" and "dried leaves," is one of the major diseases of cucumber. The damage is widespread and serious. 1, symptoms: seedling stage, adult stage can be made of ulcers, mainly damage the leaves. At the seedling stage, the cotyledon was initially damaged and faded into a green macular, which fades after yellowing. In the adult stage, the onset begins with the lower leaves and gradually spreads upward. At the early stage of disease, the leaf surface was spotted with water-stained lesions. In the morning, the lesions were gradually enlarged, the lesions gradually expanded, and the veins were limited to fade out of the yellow spots. When the humidity was high, the black mold layer grew on the back surface of the leaves, and the latter disease was found. The spots were broken or contiguous, causing the leaves to curl up and dry, and the severe patches were yellow. (1) Pathogens. Cucumber downy mildew is a fungal disease. It is caused by infection by flagella flagellum, Pseudoperonospora genus. (2) Incidence conditions. The suitable temperature for the occurrence of downy mildew is 15 -24 degrees, and the incidence is lower than 15 degrees or higher than 30 degrees. The relative humidity of the air is more than 80%, and the sporangia does not occur when the phase humidity is less than 60%. The germination and invasion of the sporangia must be under the condition that there are water droplets on the leaf surface, otherwise it will not be pathogenic. (3) Control methods: 1. Select resistant varieties. 2. Strengthen cultivation and management, increase organic fertilizers on seedbeds, use nutritious seedlings as far as possible, choose land plots with high topography and good drainage, separate greenhouse cucumber seedlings from production greenhouses, reduce air humidity in sheds, timely cultivator, raise ground temperature, Remove diseased leaves and old leaves in time to improve ventilation and light transmission conditions. (4) Formula fertilization: During the middle and late stages of cucumber growth, the foliar spray [gold full warehouse expansin] can water 30 kg per bag, which can improve cold resistance and disease resistance, promote photosynthetic efficiency, and increase sugar content. Increase production by more than 30%. Tel: 0311--87753859, 87831639. (5) Chemical control: At the beginning of the disease, 25% of the toxic WP wettable powder 800 times, 40% EB aluminum wettable powder 300 times, 75% chlorothalonil wettable powder 500 times, 64% antivirus can be used. Wet powder 400 times, spray once every 7-10 days, even spray 3-4 times, such as spraying with [Feng Mancang foliar] more effective. (6) 40% chlorothalonil smoke can be used in the wet room greenhouse. 200-250 grams of medicine is used in each room. The medicine is divided into 4-5 parts. It is ignited in the evening and closed. The next morning, it is ventilated and smoked every 7 days. Once, smoke 3-4 times. phone