The onset of potato leaves usually begins at the tip or edge of the leaf. At first, chlorosis spots appeared in the leaf margin, and then gradually expanded. Excessive humidity is conducive to the spread of the lesion until it spreads to the whole leaf. Late blight can occur on potato roots, stems, leaves, flowers, fruits, stolons and tubers, which is the most intuitive and easy to judge symptoms and spots on tubers. Most of them start from the tip or edge of the leaf, and irregular small spots appear first. With the aggravation of the disease, the spots continue to expand and merge.

Potato diseases are caused by many other factors. Therefore, it is necessary to take preventive measures from the beginning, establish a disease-free seed reserve base and plant disease-free potatoes. Strengthen field management, implement crop rotation, increase the application of phosphate fertilizer and calcium fertilizer, and prohibit the application of alkaline fertilizer. Sporocysts of pathogenic bacteria are solitary or bunched, protruding from stomata, colorless, slightly thinner than hyphae, with nodular expansion on branches, with the size of 658 ~115 μ m× 6.5 ~ 7.5 μ m. ..

Select disease-resistant varieties and disease-free potatoes to reduce the source of primary infection. Strengthen field monitoring and investigation, and find the central diseased plants in time. Implement unified prevention and control rules for contiguous children to improve the prevention and control effect. If you spray a spray on the potato to prevent the potato from sprouting, if you are infected with the stem or petiole of late blight, ladybug and other pests, it will stink. And it will produce brown stripes. In severe cases, the leaves will wither and curl, and the whole plant will be black and rotten, giving off a rotten smell.

Phytophthora infestans mainly overwinter in seed potatoes with hyphae and become the main primary infection source in the next season. The disease is a typical epidemic disease, and its occurrence and prevalence are closely related to climatic conditions. When the conditions are suitable, the disease can break out quickly before and after the flowering of potato plants, and the leaves will appear irregular-shaped spots. At first, small brown spots like water stains will appear on the tips and edges of leaves. When the weather is wet, the diseased spot will quickly expand to brown to black, and finally the whole leaf will rot and the diseased leaf will smell bad.