Symptoms and Control methods of main Diseases and pests in Potato

The main potato diseases are: potato ring rot, potato cancer, potato late blight, potato early blight, potato black shank, potato bacterial wilt and so on. The main pests are: potato tuber moth, 28 ladybug, underground pests (ground tiger, grub, golden needle beetle and mole cricket, etc.). Among them, there are three kinds of quarantine pests in the country: potato tuber moth, potato ring rot and potato cancer.

Main diseases of potato

Potato ring rot

The disease in the field is generally after the flowering stage, the initial symptoms are chlorosis between the veins, then the leaf edge or the whole leaf is yellow and withered, and curl upward, the disease starts from the lower leaves of the plant, and then gradually develops to the whole plant. Due to the different environmental conditions and disease resistance of varieties, the plant symptoms are also very different, which can cause shoot stem and leaf wilting and withering spots, and underground tuber vascular bundles occur ring rot. Withered spot type: the disease occurs first on the top of the compound leaves at the base of the plant, the leaf tip and leaf margin are green, the mesophyll is yellow-green or grayish green, the leaf tip turns brown and withered, the leaf turns inward, and the vascular bundles of the diseased stem turn brown. Wilting type: it occurs from budding, the leaf wilts and dies from bottom to top, the leaf edge curls longitudinally to the leaf surface, showing dehydrated wilting, the vascular bundle at the base of the stem becomes yellowish or yellowish brown, and the plant dies ahead of time.

The tuber is mildly susceptible and has no obvious symptoms on the outside. With the development of the disease, the skin darkens, the bud eye blackens and dies, and there is also a surface crack. After cutting, the vascular bundle shows a milky white or yellowish-brown ring-shaped part, light ones squeeze with their hands, milky yellow bacterial mucus flows out, the seriously diseased tubers turn dark brown, ring-shaped cavities are formed, and potato skins and heart are easily separated by hand extrusion, often accompanied by saprophytic bacteria invasion.

Prevention and control methods:

The comprehensive measures of selecting disease-resistant varieties, pulling out diseased plants in the field and selecting low-toxic pesticides should be taken. The diseased plants were dug up and treated centrally at the seedling stage and adult stage. Diseases in the field can be sprayed with 72% agricultural streptomycin 4000 times, or 2% chlortetracycline wettable powder 500x, or 77% wettable particulate powder 500x, or 25% ammonia copper water solution 300x, or 50%DT wettable powder 500x.

Potato cancer disease

After the damage of potato underground stem base, tuber and stolon, a large, rough and loose tumor was formed, which even surrounded the whole stem base, which was very similar to cauliflower. Young potatoes become deformed as a whole, while larger tubers often form malformed cancers at the bud eyes. Highly susceptible varieties form small cancers between axillary buds and stems. The number and size of cancer vary according to the infectivity of the variety, the susceptibility sooner or later, the number of infection points and the degree of disease. The cancer is white at the beginning, bright in color, gradually green after seeing the light, and finally turns brown to black and rotten. The stem, pedicel, calyx and leaf back of highly susceptible varieties can grow sessile and clustered leaflets with main veins but no branches.

Prevention and control methods:

(1) strict quarantine and delineation of epidemic areas and protected areas. The transfer of seed potatoes to the epidemic area is strictly prohibited, and the soil of the diseased field and the plants growing on it are also strictly prohibited from moving out.

(2) selecting disease-resistant varieties. There are great differences in resistance among varieties, and the potato "rice grain" varieties in our province show high resistance, which can be selected according to local conditions.

(3) it is not suitable to grow potatoes in seriously diseased areas, and non-Solanaceae crops should be planted in general diseased areas according to the actual situation.

(4) strengthen cultivation management, apply clean manure in ploughing, increase phosphorus and potassium fertilizer, dig up diseased plants and burn them in time.

(5) disinfect the soil in the diseased area if necessary.

(6) early application of pesticide for prevention and treatment. The fields with small slope and inconvenient water sources are irrigated with 1500 times of 20% triadimefon EC from seedling emergence to full seedling stage; in fields with inconvenient water sources, 20% triadimefon emulsion can be sprayed at seedling stage and bud stage to draw 2000 times, each mu sprayed 50% 60 liters of medicine, which has a certain control effect.

Potato early blight

The seedlings were killed to form a standing wilt, resulting in dead seedlings. In the adult stage, the disease of leaves is common and severe. The disease of leaves usually starts from the lower leaves and develops to the upper leaves. At first, small chlorotic spots were formed on the leaves, and then gradually expanded to form round or irregular disease spots of different sizes. The disease spot is brown to dark brown, the edge has light green or yellow halo ring, and there are obvious concentric processes in the middle of the disease spot. In severe cases, multiple disease spots can be combined into irregular spots, resulting in early withering of leaves. Petiole disease spot oval, dark brown to black, with wheel marks. When the disease spot is large, it causes the leaves to wilt and die. The stem is also prone to disease. The disease occurs in the stem, especially in the branches. The disease spot is oval, long fusiform or irregular, brown to dark brown, slightly sunken, the wheel pattern is not obvious, and the surface is gray-black mildew. Stems and branches are easy to break branches from diseased spots. Fruit disease often occurs near the pedicel, resulting in nearly round or oval, 10-30 mm in diameter sunken spot. The disease spot is brown to dark brown with obvious wheel lines and is covered with a black mildew layer. The disease spot is hard, generally does not rot, and sometimes cracks from the disease spot in the later stage. Potatoes can sometimes damage tubers, forming round or irregular, dark, slightly sunken, clear-edged spots. The disease can be half a centimeter deep under the skin, and the potato meat turns brown and dry rot in the later stage.

Prevention and control methods:

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