What are the reasons for the large number of curling and drying of pumpkin leaves? What control measures should be taken? Pumpkin downy mildew can occur in the seedling and adult plant stage. Also known as "bubble hemp dry", mainly affecting the pumpkin leaves. In the early stage of the disease, there will be water-soaked yellow spots on the back of the leaves. When the spots gradually expand, yellow-brown irregular polygonal spots will appear. If the humidity in the growing environment is too high, a gray-black mold layer will grow on the back of the spots. A typical feature of the disease is the progression from the lower leaves to the upper leaves. When the disease is severe, the spots tend to join together, causing the leaves to turn yellow, dry, and break easily, and the plant to turn yellow, as if it were burning.

1, pumpkin as an affordable vegetable, loved by consumers. The market demand is huge, and vegetable farmers also like to plant. Especially greenhouse pumpkin can be listed as early as possible, with high economic benefits. Therefore, many farmers will choose to continue growing pumpkins to make full use of the greenhouse. Downy mildew is a fungal disease. The pathogen can overwinter in the greenhouse in the form of spores. If a single pumpkin is planted in a row, it will only make the bacterial population bigger and bigger. Of course, where there would have been no disease before, there will be a massive outbreak this year.

2, cultivate disease-free strong seedlings. Cultivate disease-free pumpkin seedlings is also a key link in the prevention and control of downy mildew from the source. First of all, we should strictly control the breeding conditions, comprehensive disinfection of the seedbed, strengthen the water and fertilizer management during the seedling period, timely ventilation, seedling refining, cultivate pumpkin seedlings, disease-free seedlings, from the source to control the occurrence of downy mildew of pumpkin. Underground drip irrigation. We must change the bad habits of flat bed planting and flood irrigation. It is recommended to use the ridge mulching cultivation method, planting pumpkin seedlings on the ridge, and drip irrigation under the membrane, which can not only reduce water consumption and save water resources, but also effectively reduce the air humidity in the shed, avoiding the high temperature and high humidity environment conducive to the spread of downy mildew.

3, increase the amount of carbon dioxide in the shed. For greenhouse cultivation of pumpkin, we can control downy mildew by increasing carbon dioxide. When the swimming spores of the downy mildew pathogen swim in the water droplets, they will invade the open stomata of the plant. When the carbon dioxide concentration in the temperature chamber is increased, the stomata of the plant's leaves will partially close, which will impede the invasion of downy mildew in pumpkins, which in turn will provide some protection against the disease.