Cucumber powdery mildew

　　1. Symptoms: In the early stages of cucumber powdery mildew, small white powdery spots appear on the upper or lower surfaces of the lower leaves, which later expand into circular, powdery lesions. Under favorable conditions, these white powdery spots continue to spread and coalesce into large, irregularly edged areas covered with a dense layer of white powder that completely covers the entire leaf, giving it the common name "white mold." In the later stages of the disease, the white powder turns grayish-white, and the entire leaf becomes yellow-brown and eventually dries up.

　　2. The prevention and control methods are as follows:

　　2.1 Select disease-resistant varieties.

　　2.2 Seed Disinfection: Soak the seeds in a suspension of 1% Antifungal Suspension (20 ml) diluted in 10 kg of water for 1 hour to eliminate powdery mildew pathogens carried by the seeds.

　　2.3 Cultivation Management ① Thoroughly remove weeds and residual plant debris from the greenhouse to prevent pathogen harborage; ② Before planting, disinfect the growing medium with fungicides such as 50% carbendazim; ③ After transplanting cucumber seedlings, minimize watering as much as possible to avoid excessive vegetative growth. Control the application rate of nitrogen fertilizer and pay attention to increasing the application of phosphorus and potassium fertilizers. During the fruit-setting stage, increase the amount of fertilizer and water, and apply foliar micronutrient fertilizers in a timely manner to prevent premature plant senescence and enhance disease resistance. ④ Promptly remove diseased plants or diseased leaves.

　　2.4 Chemical Control: Use a 1,000-fold dilution of 70% methyl tobuazin wettable powder, or a 1,000- to 1,500-fold dilution of 15% rust inhibitor, or a 500- to 800-fold dilution of 75% chlorothalonil wettable powder. Spray every 7 to 10 days, repeating the treatment 2 to 3 times. (Extracted from: Zhejiang Agricultural Network)