First, the symptoms
Early blight of potato mainly damages the leaves. In severe cases, it also damages the petioles and stems. The leaves are infected, the lesions are gray to dark brown, round or nearly round, and sometimes the development of lesions is limited by the veins to be polygonal or irregular. The lesion has a concentric ring pattern. When it is wet, a black layer of mildew develops on the lesion. The lesions fuse with each other for a long time in the area of ​​large patches, resulting in partial or total dead leaves. Stems and petioles infected, resulting in dark brown slightly concave, elongated or long fusiform dark brown lesions, sometimes with concentric rings. Some stems were infected and the skin was light brown sponge-like dry rot.
Second, transmission routes and conditions
The potato early blight pathogen is Alternaria solani, a fungal species. The wintering of pathogens with conidia and mycelium on diseased or diseased tubers is the primary source of infection in the fields of Hunchun. The newly-produced conidia on diseased plants are spread by wind and rain, and are suitable for Under conditions of temperature and humidity, invading from the stomata, wound or epidermis, and re-infection for many times, the disease spreads and expands.
The weather conditions required for the occurrence of potato early blight are not very strict and may occur in normal years. Conidial germination has a suitable temperature of 26°C-28°C. When the leaves have condensation or water droplets, the temperature is favorable, which is conducive to disease. Drought, lack of fertilizer, easy to disease when plant growth is weak.
Third, control methods
1. Agricultural control
Choose fertile sandy loam soil or loam soil for potato cultivation. The high quality decomposed organic fertilizer is used as a base fertilizer, and nitrogen, phosphorus and potassium compound fertilizers are applied as a seed fertilizer at the time of sowing, but potassium chloride should not be used. When potato blossoms, spray 0.1% potassium dihydrogen phosphate. If the plants are long, they can spray 100ppm paclobutrazol to promote healthy growth and increase resistance to disease. In severe cases, it is necessary to rotate with non-solanum vegetables.
2. Chemical control
In the early stage of disease, 75% chlorothalonil WP 600 times, 64% WP 500 times, 50% carbendazim 500 times, and 77% WP 500 times Liquid, 50% acetaminophen WP 1000 times liquid spray control, 7-10 days once, even spray 2-3 times.
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