A Detailed Guide to the Latest Control Methods for Cucumber Phytophthora Blight
Cucumber phytophthora blight can infect plants from the seedling stage to the mature plant stage. When seedlings are infected, dark green, water-soaked rot first appears on the tender tips, gradually dries up, and forms bare tips. At the mature plant stage, it mainly affects the base of the stem and the nodes of tender stems, starting as dark green water-soaked lesions, which then become soft, noticeably constricted, and the leaves above the affected area gradually wilt. Let us take a look together at the control methods for cucumber phytophthora blight!
Occurrence Pattern of Cucumber Phytophthora Blight
Cucumber phytophthora blight is a fungal disease. The pathogen overwinters in the soil or manure with diseased plant debris. In the following year, when conditions are suitable, it produces sporangia that spread through wind and rain, irrigation water, and water droplets. The optimum temperature for disease development is 28 to 30 degrees Celsius. When rainfall is heavy, rain occurs frequently, or shallow water is abundant and large in volume, the disease is prone to occur and spreads quickly. Therefore, under conditions of low-lying terrain, poor drainage, and high humidity, the disease is severe.
Conditions for Cucumber Phytophthora Blight Development
The pathogen mainly overwinters as mycelium, oospores, and chlamydospores with diseased plant debris in the soil or manure, and spreads through wind, rain, and irrigation water. The optimum temperature for disease development is 28-30°C, and soil moisture is an important factor affecting the epidemic level of this disease. In years with high summer temperatures, heavy rainfall, and many rainy days, the disease is prone to become epidemic and cause severe damage. In addition, low-lying terrain, poor drainage, and continuous cropping make plants susceptible to the disease. In protected cultivation, at the turn of spring and summer, after opening the ventilation openings at the front of the greenhouse, the disease is prone to develop rapidly.
Control Methods for Cucumber Phytophthora Blight
1. Agricultural measures: Choose disease-resistant varieties, such as Jinchun No. 3, Jinza No. 3, Jinza No. 4, Zhongnong 1101, Longza Huang No. 5, Zaofeng No. 2, etc. Use Yunnan black-seeded pumpkin as rootstock for grafted seedling cultivation. Adopt high-ridge cultivation and cover with plastic film to reduce the chance of pathogen infection of plants. Avoid flood irrigation and avoid excessively high soil and air humidity. In open-field cultivation, during the rainy season, promptly drain accumulated water from the field, and promptly pull out and remove central diseased plants once found.
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2. Disinfection treatment: An effective method for seed disinfection is to soak seeds in a 800-fold dilution of 25% metalaxyl wettable powder for 30 minutes, then promote germination and sow. The method for soil disinfection of seedbeds or greenhouses is to mix 8 grams of 25% metalaxyl wettable powder per square meter of seedbed with soil and spread it on the seedbed. For protected cultivation, before transplanting, spray the ground with a 750-fold dilution of 25% metalaxyl wettable powder.
3. Chemical control: The key to controlling cucumber phytophthora blight in open fields is to start spraying one week before the rainy season arrives, once every 7 days, for 3 consecutive sprays. Optional agents include a 600-fold dilution of 64% oxadixyl-mancozeb wettable powder, a 1000-fold dilution of 25% metalaxyl wettable powder, a 1200-1600 fold dilution of Yemeishaxing wettable powder, a 600-fold dilution of 50% metalaxyl-copper wettable powder, etc. Practice has shown that spraying a 500-fold dilution of 70% mancozeb wettable powder or a 1:0.8:200 Bordeaux mixture before disease onset for protective spraying gives very good control efficacy.