The chlorotic yellowing of cucumber leaves is a symptom of cucumber downy mildew. Downy mildew is the most common type of disease on cucumbers. It can be infected at the seedling stage and adult stage. It usually starts from the middle leaves of the plants and gradually expands upward and downward. The chlorotic spots appear on the leaves at the beginning of the disease, and the tan irregular spots are formed after expansion. Spots of necrosis on the back of the leaves will see small, colorless or light yellow droplets. The lesions quickly expanded and became polygonal due to their expansion limited by the veins within 1 to 2 days, especially in the morning when the horny lesions were the most obvious in water-immersed condition and retreated slightly at noon. In the later period, lesions and nearby leaves were rusty. When the disease is heavy, the leaves are full of lesions and connect with each other, causing the leaf margin to curl and dry, and finally the leaves are yellow. Control methods: 1. Protection of the ground floor room can use smoke or dust method. 2. Spray method, after the discovery of the central disease strain, 70% eth phosphine manganese zinc wettable powder 500 times or 72.2%, 800 grams of Preclosure, 58% radomeril-manganese zinc wettable powder, 72% cream Pa WP 700 times, 72% cream Qingqing or 56% wet powder 750 times liquid, sprayed every 7 to 10 days. Ice Roller,Ice Face Massager,Ice Massage Roller,Ice Ball Face Massager Ningbo Prestigeplus Commodity Co.,Ltd , https://www.prestigemedics.com