How to control powdery mildew of pumpkin when the leaves are covered with white spots?

Pumpkin powdery mildew can occur during the growth period, especially in the middle and later stage. It mainly infects leaves, petioles and stems. In the early stage, there were nearly round white powdery mildew spots on both sides of pumpkin leaves, which were mostly on the leaf surface, and then gradually expanded, and the powdery spots connected into large blocks. when the disease was serious, the whole leaf was covered with white powder, and the leaf tissue under the white powder was light yellow at first, then turned brown, and then turned gray and white. the leaves dried and curled up. The symptoms of petiole and tender stem are similar to those of diseased leaves, but less powdery.

Pumpkin

Disease conditions: the incidence of pumpkin powdery mildew reached its peak when high temperature, high humidity and high temperature and drying alternately appeared. Urea and other nitrogen fertilizer is applied too much, planting is too dense, wet fields are prone to disease or serious disease. After production, the pathogen overwintered on the old plants and diseased bodies of pumpkins.

Integrated prevention and control:

(1) select disease-resistant varieties. Now more Japanese Yixiang pumpkin, chestnut pumpkin and orange red pumpkin are planted, which have certain disease resistance, but the purification and rejuvenation work is indispensable, and disease-free seedlings are selected.

(2) seed disinfection: before sowing, the seeds were exposed to the sun for 2 days to kill epidermal miscellaneous bacteria and increase germination potential; soak the seeds with 50 ℃ 55 ℃ warm water for half an hour, the temperature dropped to 30 ℃ and continue to soak the seeds for 8 ℃ for 10 hours, then disinfect the seeds with 1% potassium permanganate solution for 30 minutes, rinse and germinate under 28 ℃-30 ℃ for 4872 hours, and sow seeds when white.

(3) strengthen management and rational fertilization: rotation with Gramineae crops for 2-3 years. 5000,000 kg of mature farm manure, 20 kg of ternary compound fertilizer, 15 kg of potassium chloride and 5 kg of urea were applied per mu. During the extension period, there is no topdressing, and during the pumpkin expansion period, 20 kg of potassium sulfate compound fertilizer is applied per mu, and the soil is kept moist and drained in time after rain. Remove the basal disease and old yellow leaves in time, bury them deeply or burn them. Strengthen the ventilation and light transmission in the field and enhance the stress resistance of pumpkin plants.

(4) foliar spray protective film: before or at the initial stage of the disease, 99.1% dipterex 300Mel 500 times liquid was sprayed on pumpkin leaves to form a protective film. 5Mel was sprayed once every 7 days, and 2Mel was sprayed three times in a row.

(5) Chemical control: from late April to July, medication should be used at the right time. Before the occurrence of the disease, 53.8% can be selected to kill 2000 1000 times of the liquid. At the initial stage of the disease, you can choose 10% Shigao 1500 times liquid, or 40% Fuxing 8000 times liquid, or 43% Pulek 5000 times liquid, or 12.5% Suopoli 2000 times liquid, or 2% plus rice 600 times liquid for spray, 7 Mel 10 days spray once, 2 Mel 4 times in a row. It can also be prevented and treated with 600 times baking soda. Individual leaves are sprayed when there are 1 Mel and 2 disease spots. 3 Mel is sprayed once every 4 days and 4 Mel is sprayed 6 times in a row. Baking soda can not only prevent diseases, but also promote growth, and increase pumpkin yield by 10%. When spraying, use a small aperture spray plate as far as possible to reduce the leaf humidity.