Diseases of potatoes
Jul 03, 2018
Late blight. Grayish- or dark-brown spots appear on the lower leaves of the bush. On the underside of the affected leaves, a white fluffy coating is formed, which is the sporification of the fungus. On the stems and petioles of leaves, the disease manifests itself in the form of brown bands. Tuber formed slightly depressed, sharply delineated brown spots, penetrating into the pulp in the form of light brown streaks or streaks.
Control measures. Cleaning and destruction of affected plant residues, timely and deep hilling before the tops are closed, removing and destroying the affected tops before cleaning( 7-10 days), drying the tubers before storing them. In the period from budding to the beginning of flowering of potatoes, the first spraying of plants with one of the following preparations is carried out: 1% solution of the Bordeaux mixture( 100 g of copper sulfate and 100 g of lime for 10 liters of water), hom( 40 g per 10 liters of water).The flow rate of the working fluid is 6-8 liters per 100 m2.
Early dry blotchiness. The leaves and stems are affected. The leaves are rounded-angular, with concentric circles macrosporia spots. After 12-14 days on the leaves there are spots of alternaria without concentric rings. The disease develops rapidly, the spots merge and become discolored. The leaves become fimbriated, dry up. On the stems and petioles the spots are elongated. The affected tops wither long before the end of vegetation.
Potato cancer hits tubers and stolons. On the affected tubers are formed growths of different shapes and sizes. In dry, hot weather, the disease manifests itself in the form of warts, similar to the common scab.
Control measures. Affected tubers can not be used for food or foraging cattle. The cancer is disinfected with bleach, kerosene and buried to a depth of at least 1 m.
Risectoniasis ( black scab) infects tubers, sprouts, stools and stems. On the tubers are formed black solid sclerotia adhering to the peel, sometimes a thin black mesh that spreads over the entire surface or part of the tuber. Affected sprouts are covered with dark brown spots and ulcers, cracked in the lesions and die. On the stools the disease manifests itself in the form of brown spots and streaks. On the root part of the stems, in wet weather, white felt coating appears. The defeat is accompanied by a slight twisting of the upper leaves, the appearance of a violet color on them, the formation of air tubers.
Control measures. Planting healthy tubers in the optimal time;use of overgrown manure or compost;timely weeding and tillage;Harvesting before the appearance of sclerotia on tubers.
Fusarium ( dry rot) develops on tubers during the storage of potatoes. On the tubers are formed grayish-brown, slightly depressed spots. Then the flesh under the stain becomes loose, acquires a brownish color. It forms voids filled with white, yellowish or dark fluffy mycelium of the fungus. Affected tissue dries quickly, the peel wrinkles, forming folds around the original spot. Control measures. Observing the storage mode;prevention of mechanical damage to tubers during harvesting;control of diseases and pests during vegetation.
Fomoz ( button rot) affects stems and tubers, which rot during decay as dry rot. On the tubers appear depressed dark spots, the skin in the spot zone is cracked, dark brown pycnidia form inside the affected tissue. Control measures. See Fusarium.
Ordinary scab affects the tubers during the whole vegetation period. The disease develops as a flat, deep, convex and netlike form. With a strong development of the scab, the tubers are covered with a continuous crust, the germination decreases. Deep form of the disease causes cracks, through which other pathogens penetrate into the tubers. Excessive application of lime, the use of fresh manure, the cultivation of susceptible varieties, hot and dry weather during plant vegetation contribute to the development of ordinary scab. Control measures. The best predecessors for potatoes are legumes. On acidic soils lime is applied in autumn in small doses. Use varieties resistant to scab.
Powdered scab hits tubers, stolons and roots. First, brownish spots appear on young tubers, which then increase, warts appear on the spot, which turn brown. When the peel on the warts dries, it explodes in a star-shaped manner and expose the dark, powdery mass of the fungal spore. On the roots and stools are formed small gibs - at first white, then they darken and disintegrate.
Control measures. Application of microfertilizers;liming of acidic soils;Before planting, spray the tubers with homo( 20 g per 8 liters of water).
Tubular scab ( osporosis) attacks the tubers before harvesting, and signs of the disease appear during storage: near the eyelets are formed tubercles that do not burst like a powdery scab, but merge, covering a significant part of the surface of the tuber. The development of the disease is favored by the humid and cool weather during the period of tuber formation, as well as the violation of the tuber storage regime. Control measures. Application of organic and mineral fertilizers with the addition of trace elements, as well as optimal storage mode with the use of active ventilation.
Silvery scab affects the tubers - on them in the fall appear first smooth dark yellow round spots, and then impressed with a silvery sheen. The development of a silvery scab is suspended at a temperature of 1-2 ° C and an air humidity of not more than 90%.
Control measures. Alternation of crops;early removal of the foliage and harvesting tubers for seeds;adherence to the tuber storage regime.
Anthracnose ( partrosis) affects stems and tubers. In diseased plants, the leaves of the lower tier are chlorotic, the stems are angular, shortened. On the stems there are light brown spots. In dry weather, plants wither, rainy stems wax, moult and rot. On tubers during harvesting, anthracnose manifests itself in the form of dark brown fuzzy spots, under the skin on the surface of the spot formed microsclerotia. During storage at elevated temperature and humidity, the tubers develop wet rot. Control measures. Alternation of crops;control of weeds;Deep embedded in the soil of all plant residues after harvesting potatoes;planting potatoes in the optimal time;observance of storage conditions.
Black leg affects the plant during the growing season and when storing tubers. Plants lag behind in growth, the leaves, starting from the upper ones, turn yellow and twist;the base of the stems decays and turns black.
Control measures. Planting only whole and healthy tubers;removal of sick bushes.
Ring rot is expressed by wilting plants during flowering and especially after it. The leaves twist and turn yellow. The bush fades and falls apart. The tubers rot. Control measures. See Black Leg.
Brown bacterial decay ( mucous disease of potato) is manifested in the flowering phase in the form of wilting leaves and stems on sunny days. Withering leaves turn yellow and wrinkle, and leaf petioles and stems droop. Affected stems bloom, lower root part softens and rot, splitting is observed along the stem. Control measures. Alternation of crops;destruction of plant residues after harvesting of potatoes and weeds during vegetation, use of only healthy and whole tubers on the seeds, removal of diseased plants from the plantings together with tubers.