Cucumber Downy Mildew and Control Technology
Cucumber downy mildew, commonly known as "running horse" or "dry leaf", can be affected by adult plants at the seedling stage. It mainly damages leaves and stems, and suffers less tendrils and pedicels. [1] Cucumber downy mildew is the most common and most damaging disease in cucumber cultivation in protected areas. The condition is fierce, the incidence is heavy, and the spread is fast. If it is not controlled in time, it will cause devastating losses to the cucumber. Symptoms Downy mildew mainly occurs on the leaves. At the seedling stage, chlorotic spots appeared at the beginning of the cotyledon and gradually appeared yellow irregular spots. On the back surface of the cotyledons, a layer of gray and black mold appeared. As the disease progressed, the cotyledons soon became yellow and dry. In the adult stage, the leaves begin to have light green water spots. After expansion, they are limited by the veins. They are polygonal, yellow-green to light brown, and the late lesions converge to form a composite. The whole leaf is dry and curled up by the leaf margins. When the leaves on the back of the lesion gave birth to gray mold layer, when the whole plant leaves dead. Disease-resistant varieties are small and small, and the layer of back mold is also sparse. Control methods 1 selection of disease-resistant varieties. Cucumber varieties of resistance to downy mildew difference, to choose more resistant varieties. 2 Select healthy and disease-free seedlings. The nursery is isolated from the production site, and diseased seedlings are strictly eliminated when planting. 3 Selection of land. When planting in open field, it is necessary to choose a plot with high topography and well-drained land. 4 Ecological control. Reform farming methods, improve the ecological environment, implement plastic film coverage, reduce evaporation of soil moisture, reduce air humidity, and increase ground temperature. Under-membrane under-irrigation, watering in the sunny morning, no watering in rainy days, to prevent excessive humidity, dew condensation. Remove moisture immediately after watering to prevent dew condensation at night. Strengthen the temperature management, in the morning the temperature of the greenhouse is controlled at 28-32°C, the highest 35°C, and the relative humidity of the air is 60%-70%. Do not vent the air prematurely every day. 5 Scientific fertilization. Apply basal fertilizer. Don't apply excessive nitrogen fertilizer during the growth period to increase the disease resistance of the plant. The incidence of plants is often related to the imbalance of their "carbon-nitrogen ratio" in vivo. When the carbon content is relatively low, they are easy to develop. According to this principle, the resistance to diseases of cucumber can be improved by spraying fertilizer on leaves and increasing the proportion of carbon. 6 high temperature stuffy shed. Generally sealed in greenhouse at noon for two hours, so that the upper plant temperature reached 44-46 °C, not more than 48 °C, can kill the shed within the fungus, once every 7 days, 2-3 times Can basically control the development of the disease. In short, the use of measures to control temperature and humidity that are not conducive to the growth and development of pathogens and to reduce the development of the disease is an effective prevention and control of cucumber downy mildew disease prevention technology. Chemical control (1) Pay attention to timely spraying protection and prevention. For prevention, before the occurrence of the disease, spray 25g of frosted red, 50ml of high-yield red, and 30kg of evenly sprayed water. Treatment plan: At the beginning of the disease: Frost fly 30g + high-yield red 50ml watered 30 kg with 2-3 sprays, 3 days sprayed once, and then replaced with control after prevention. In the late stage of onset: Qiyue 2 40g + frost fly 25g + high-yield red 50ml watered 30 kg even sprayed 2-3 times, 3 days sprayed once, after control to prevent. Remarks: Chihyu 2 can be used to increase or decrease the dosage according to the severity of the disease. (2) Spray 50% Carbendazim WP 600 times, or 70% EDP Mn Zn wettable powder 500 times, 72% KE Kang WP 800 times, 56% azoxystrobin before onset Chlorothalonil 600 times liquid, with 150 million live spores per 667 square meters / gram of Trichoderma 266 grams of wettable powder 50 liters of water, spray every 5 to 7 days. 90% triethylphosphonate wettable powder can be used for the pharmaceutical 400 to 500 times liquid, 38% cacodylate 800 times times, 25% metalaxyl wettable powder 800 times, Vibrio ficilipenium 1200 Times of liquid; 64% anti-virus WP WP 600 times, 70% phospine aluminum Mn Zn wettable powder 500 times, 72% Ke Kang WP 800 times, 75% chlorothalonil WP 500 times liquid. Water Test Kits,Well Water Test Kit,Water Testing Strips,Water Test Kit Home Depot Changchun LYZ Technology Co., Ltd , https://www.lyzstrips.com