Potato late blight is an annual epidemic disease, which mainly occurs at the early flowering stage of plants and is a mechanism disease. Therefore, the occurrence of potato late blight is closely related to meteorological conditions. Generally speaking, when the weather is wet and gloomy, it is foggy in the morning and evening, and there is a lot of dew, which is conducive to the occurrence of diseases. After the emergence of the central diseased plant, the conidia sac produced by the diseased part re-permeates through the spread of wind and rain, which can cause large-scale disease 1 ~ 14 days after the onset. Different potato varieties have different disease resistance. Compared with disease-resistant varieties, sporangia reproduce quickly after plague and are easy to be infected. In addition, the same variety of potato plants grow, and the disease resistance of plants decreases when they bud, which is prone to diseases.

As a super-infectious source, strain sweet potato has an important relationship with the spread of plague. Potato late blight occurs all the year round, the pathogen will spend the winter in the soil and the sick and disabled, and non-standard management and farming operations will further spread the pathogen, leading to the occurrence and epidemic of late blight. Potato late blight mainly harms leaves, petioles and tubers. When the leaves are diseased, the diseased spots usually appear at the leaf ends and edges, and the shape of water stains begins to fade, and then gradually expands to round dark green spots. When the humidity is high, the diseased spots expand faster, and then become dark brown spots after expansion. The edges of the diseased spots are not obvious, and a white fungus layer often appears on the back. The stems on the ground often form brown spots with different lengths. When the environment is wet, there will sometimes be a white sparse fungus layer. When the tuber is sick, it will form light brown or gravel irregular spots with a slight depression. The mottled potato meat has different degrees of brown necrosis, which eventually leads to the corruption of sick potatoes.

breeding disease-resistant varieties is the most economical, environmentally friendly and effective measure to prevent potato late blight. Guizhou and other southwest regions can choose CFK-69.1, I-185 and other varieties with good resistance and productivity introduced by International Potato Center for production. After the potato seeds are taken out of the kiln, they are ground in the sun for about 2 hours to remove rotten potatoes and deformed potatoes, and then germinate in a place with scattered light. During germination and germination, cut into pieces, leaving one or two bud holes respectively, weighing about 4g, and then mix the soil in the vegetation meeting for sowing with the instructions of methyl frost zinc ring.

Choose a plot with high terrain, loose soil and good drainage to plant potatoes, and do a good job of ditch drainage to reduce the humidity in the field and reduce the occurrence of diseases. Avoid partial application of nitrogen fertilizer and apply phosphorus and potassium fertilizer appropriately. Popularize high ridge cultivation, especially in areas with rainy and good moisture, it is best to use large ridges for planting, so as to thicken the topsoil layer and prevent this pathogen from infiltrating potatoes. Reasonable close planting, control the length of plants. If you sow in time, it is suitable for the sowing period. In the fragile disease and growth period, that is, the flowering period of the county thunder, it is best to miss the concentration period of the rainy season. Take turns reasonably, avoid annual cropping or trap with Solanaceae and Cruciferae, and prohibit annual cropping with tomatoes. Timely find and clear the central diseased plants, clear the plots and reduce the spread of pathogenic fungi.