Potato Disease Prevention and Control Methods and Cultivation Techniques

I. Late Blight (1) Conditions for Onset. Potato late blight, also known as blight or potato plague, is a devastating disease of potatoes. In plots that are low-lying, poorly drained, and have high field humidity, or in plots with excessive nitrogen fertilizer application, the disease tends to be severe. When temperature and humidity are suitable, late blight spreads rapidly, and diseased plants wither and die in patches. (2) Symptoms. On affected leaves, round or irregular dark green water-soaked spots first appear at the leaf tips and margins. After expanding, they become large brown lesions. When humidity is high, a ring of white mold grows at the boundary between the diseased and healthy parts. When stems are affected, slightly sunken brown streaks appear, and white mold is also produced under moist conditions. When tubers are affected, brown slightly sunken lesions appear. (3) Control Methods. 1. Select disease-resistant varieties and disease-free seed potatoes. 2. In heavily infested fields, carry out crop rotation with non-solanaceous vegetables for more than 3 years; spring potatoes should be spaced 300-500 m from tomato fields. 3. Strengthen cultivation management, apply nitrogen, phosphorus, and potassium fertilizers in a balanced way, appropriately increase potassium fertilizer to enhance disease resistance. Dig drainage ditches to lower field humidity, promptly remove diseased plants in the field, and burn them in a centralized manner to reduce disease incidence. 4. Chemical control. At the early stage of disease onset, spray immediately to control its spread. Spray once every 5-7 days, for 2-3 consecutive sprays. Commonly used chemicals include 64% Sandofan at 500-750 times dilution, or 58% wettable powder at 500-600 times dilution, or 80% Dacotech wettable powder at 500 times dilution, or 40% Daconil suspension concentrate at 500-600 times dilution.

II. Ring Rot (1) Symptoms. Symptoms generally begin to appear around flowering. The branches and stems of diseased plants shorten, leaf color turns yellow and wilts, leaf veins turn yellow, and dark brown patches appear, with leaf margins curling slightly upward. In mildly affected tubers, there are no obvious external symptoms. In severely affected tubers, the diseased parts turn dark brown, with ring-shaped cavities appearing, sometimes complicated by soft rot, leading to complete decay. (2) Control Methods. Select disease-free seed potatoes, thoroughly eliminate diseased tubers before seed retention and cutting, and disinfect knives before cutting potatoes. Promptly pull out diseased plants when found. Pay attention to controlling underground pests, practice crop rotation, and select disease-resistant varieties.

III. Bacterial Wilt (1) Conditions for Onset. Potato bacterial wilt, also known as bacterial wilt disease, is a serious disease of potatoes. It is severe in areas with high temperature, high humidity, and abundant rain. Planting diseased seed potatoes, continuous cropping, low-lying terrain, and slightly acidic soil make the disease more likely to occur. (2) Symptoms. At the early stage of onset, lower leaves wilt during the day and recover in the evening. After two days, they no longer recover, gradually spreading from bottom to top. After 4 days, the stems and leaves of diseased plants wilt and die. (3) Control Methods. Potatoes should not be continuously cropped with solanaceous plants and crops such as peanuts. Rotation with rice has a good disease-prevention effect. Strengthen cultivation management, choose plots with higher terrain and good drainage for planting; apply more organic fertilizer and increase potassium fertilizer. For acidic soil, spread 50-75 kg of lime per mu before plowing and harrowing to make the soil slightly alkaline, which can reduce disease incidence. When diseased plants are found, immediately pull them out and burn them, and use chemicals to drench the roots, once every 7 days, for 2-3 consecutive drenchings, using 0.25 kg of chemical solution per plant, which has a good disease-prevention effect. Commonly used chemicals include 500% Xiaojunling at 700 times dilution, or Kaoshan water-dispersible granules at 800 times dilution, or Keshade at 1000 times dilution, or 20% lime water.

IV. Viral Diseases (1) Causes. Potato viral diseases are a serious disease of potatoes, mainly because virus-carrying seed potatoes are planted. Extensive cultivation management, lack of fertilizer, and lack of water will aggravate the condition. (2) Symptoms. After onset, plants become deformed and stunted, and yield decreases. Due to the damage caused by viral diseases, the performance of potato seed potatoes can degenerate. After potatoes are infected, they mainly show two types: crinkle mosaic disease and leaf roll disease. 1. Crinkle mosaic disease. Dark green and light green alternate on the leaves, the leaves become smaller, the leaf tips bend downward, the leaves crinkle, and the whole plant becomes dwarfed. 2. Leaf roll disease. The leaf margins curl upward, and in severe cases become cylindrical. Diseased leaves are slightly smaller than healthy leaves, with a lighter leaf color, and sometimes the underside of the leaves turns red or purplish red. (3) Control Methods. 1. Strengthen cultivation management. Increase row spacing, reduce plant spacing, cultivate with high ridges and deep furrows, apply sufficient base fertilizer, increase phosphorus and potassium fertilizers, irrigate reasonably, and promptly pull out diseased plants to reduce disease incidence. 2. Control aphids to prevent disease. After potatoes emerge, spray immediately to prevent aphids from transmitting the virus. 3. Chemical control. Spray with 1.5% Zhibingling at 1000 times dilution plus 20% Virus A at 600 times dilution, once every 7 days, for 3-4 consecutive sprays, with a relatively good disease-prevention effect.