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Why aloo is peela !?
Answers
Potatoes grow as a summer crop in cooler climates and as a winter crop in warmer climates. Potato plants turn yellow at the end of the growing season, and this is normal. But if the potato plant yellows before the tubers are ready for harvest, your plants may be infected by wilt fungi or infested with psyllids.
Verticillium Wilt
Verticillium wilt (Verticillium dahlia) of potatoes causes the lower leaves to yellow and wither. The symptoms of infection spread upward until your entire plant is yellowed and wilted. The vascular tissue of the potato plant stems also becomes light brown. This can be seen best at ground level. Some tubers may be discolored near the stem end. Verticillium fungus can persist in the soil for a long time, and while infection is favored by cool weather, the development of symptoms is favored by high temperatures. Infection limits or prevents water uptake, so signs of infection may be more severe during periods of hot weather or when potatoes are stressed for water.
Fusarium Wilt
Fusarium wilt (Fusarium solani f. sp. eumartii) symptoms are similar to verticillium wilt, but with fusarium wilt, the tissue between the leaf veins turns yellow, and then turns brown. Symptoms spread up the stems and the vascular tissue in the stems and tubers may show a brown discoloration. Fusarium wilt symptoms are typically more severe during hot weather when your plants are water-stressed. The fungus that causes fusarium wilt can survive for long periods in the soil, even without a host. Infection spreads from the roots up into the vascular tissue until it infects not just the stems, but also tubers and stolons.
Wilt Management
Because symptoms of wilt are similar, laboratory analysis of infected plant tissue is usually needed to determine which fungus is the cause, although according to University of California Statewide Integrated Pest Management Program, in most areas verticillium wilt is more common than fusarium wilt. Rotate potato crops with cereals, grasses and legumes to prevent future infections. According to University of California Statewide Integrated Pest Management Program, treatment with fungicides is rarely necessary for wilt infections in California. If fusarium wilt is a problem in your garden, rotation out of potatoes and other solanaceous crops is necessary for four to six years to reduce soil levels of the pathogen that causes infection.
Psyllid Yellows
Potato psyllids (Bactericerca cockerelli) resemble small cicadas, and are less than 1 inch long. Related to aphids and leafhoppers, adult potato psyllids have clear wings and black bodies with white markings on the first and last abdominal segments. Potato psyllid nymphs are flat and green and with short spines surrounding the edge of their bodies. Potato psyllid nymphs release a toxin when they feed that causes a condition referred to as psyllid yellows, because of the characteristic yellowing of the plant. Symptoms also include an upward curling of leaflets closest to the stem on the upper portion of the plant, which becomes more evident over time. Yellowing is initially found at leaf edges but eventually covers the entire plant. Severely affected plants may become dwarfed and pyramid shaped. According to University of California Statewide Integrated Pest Management Program, as few as three or four nymphs per plant can produce symptoms. You can use sticky traps to detect psyllid infestations before major damage occurs. Treat infested potato plants with imidacloprid or spinosad. You may need to repeat the treatment if the infestation is severe. When using pesticides, check the label for application rates and timing, and follow all recommended safety precautions.
Explanation:
Potato plants turn yellow at the end of the growing season, and this is normal. But if the potato plant yellows before the tubers are ready for harvest, your plants may be infected by wilt fungi or infested with psyllids.