How to control potato late blight

Potato (scientific name: Solanum tuberosum), a perennial herb of Solanaceae with edible tubers, is the third most important food crop in the world, second only to wheat and corn. Potato, also known as ground egg, potato, potato, etc., is the tuber of Solanaceae. Together with wheat, corn, rice and sorghum, it has become the world's top five crops. Potato is native to the Andes of South America, and the history of artificial cultivation can be traced back to southern Peru from about 8000 to 5000 BC. Potato is mainly produced in China, Russia, India, Ukraine, the United States and so on. China is the country with the largest potato production in the world. In 2015, China will launch the potato staple grain strategy to promote the processing of potatoes into steamed bread, noodles, rice noodles and other staple foods, and potatoes will become another staple food besides rice, wheat and corn.

What is potato late blight?

Potato late blight has occurred in varying degrees over the years, seriously affecting the improvement of potato quality, yield and economic benefits. therefore, it is very important to control potato late blight. Potato late blight, also known as blight, is a common and serious epidemic disease. All potato planting areas have occurred, non-resistant varieties in the epidemic of late blight, field yield loss of up to 20%-50%, light cellar loss of 5%-10%, heavy more than 30%. Late blight not only harms potatoes, but also harms tomatoes, peppers, eggplant and so on.

Disease symptoms of Potato late Blight

Potato leaves, petioles, stems and tubers can be infected. In the early stage of leaf disease, dark green water stains appeared on the leaf tip or leaf edge. When the weather was wet, the disease spot expanded rapidly, and a white and sparse mildew wheel appeared on the edge, especially on the back of the leaf. In severe cases, the disease spot extends to the main vein and petiole, causing the leaves to wilt and droop. When the climate is dry, the disease spot dries up and turns brown. Stem damage, initially showing slightly sunken stripes, when the climate is humid, the surface also produces white mold. The tuber was damaged to form a light brown or grayish purple irregular spot, slightly sunken, and the lower layer of potato turned brown. When the soil is dry, the disease is hard to shrink, and white mildew can also grow when it is wet.

Potato late blight mainly damages leaves, stems and tubers. After the disease, the area and number of leaf disease spots increased rapidly, which caused the early death of potato in the whole field, and caused tuber rot, which seriously affected the yield. This year, autumn potato in our county has a large planting area and generally grows well. Combined with the fact that Shizong has entered autumn with continuous rain, low temperature and humidity, and large temperature difference between day and night, potato late blight is easy to occur.

Control methods of Potato late Blight

1. Breeding and popularizing resistant varieties: selecting resistant varieties is the most economical and effective way to control late blight. There are great differences in the resistance of different potato varieties to late blight, because potato late blight is prone to variation, and vertical resistant varieties are easy to lose their disease resistance after several years of culture. therefore, disease-resistant varieties with multi-genes or horizontal resistance should be selected.

2. Establish the disease-free seed field and eliminate the primary infection source: because the disease-free seed potato is the only primary infection source, the establishment of disease-free seed land can greatly reduce the initial infection source and effectively prevent the occurrence of late blight. More stringent control measures should be taken to keep the land. Where there are conditions, the planting land should be more than 2.5km away from the field, so as to reduce the chance of pathogen transmission. In addition, selecting disease-free seed potatoes can also reduce the source of initial infection, while soaking seeds with chemicals can kill internal germs of seed potatoes, delay the occurrence of late blight for 20 days, reduce the disease index by about 50%, and use 25% metalaxyl 100g, plus a small amount of water immersion or spraying.

3. Strengthen field management: 1): soil preparation, high terrain selection, good drainage and planting, take measures such as soil cultivation, tobacco root removal, ditch drainage and other measures to increase the application of potash fertilizer and improve disease resistance. 2): selecting seed potatoes before sowing and eliminating bacterial tubers can reduce the number of diseased plants in the center of the field. Soil cultivation in the later stage of potato growth can reduce the chance of zoosporangium infecting potato pieces. In the epidemic year, if the seedlings were stopped early and harvested 2 weeks later, the contact between potato pieces and diseased plants could be avoided and the carrying rate of potato could be reduced.

4. Chemical control: at the initial stage of the occurrence of late blight, the diseased plants should be found and removed in time, and chemical agents should be sprayed on the plants within the range of 30mur50 meters around the central diseased plants. after that, they should be sprayed once every 7-10 days, generally 2-3 times, according to the situation. it has a good control effect. Drugs can choose 58% metalaxyl manganese zinc, 64% antiseptic alum, Dasheng MUE 45, 72% DuPont dew, 69% Anke manganese zinc, and so on. In order to reduce the emergence of pesticide resistance, it is best to use a variety of agents alternately.

In a word, potato late blight is a destructive disease with serious harm. The prevention and control of potato late blight in our county should be based on the principle of "prevention first, comprehensive control". It is necessary to take agricultural control as the basis, chemical control as the auxiliary, and the comprehensive use of a variety of control measures in order to achieve good control results.