Peanut leaf spot, commonly known as spot disease, black shank disease, etc. Is a fungal disease, is a semi-known fungi, plexus spores, black family. After the peanuts are damaged, the green leaves and leaves are destroyed and the photosynthesis declines, causing early defoliation and affecting the yield.
1, symptoms of peanut leaf spot mainly brown spot and black spot. Brown spot mainly occurs in the leaves. In severe cases, stems and petioles also suffer. The leaves were affected. The first round, near-circular, yellow-brown squad was spotted and the lesions gradually expanded to a diameter of 1-10 mm. The leaves are dark brown on the front and brown or light brown on the back with yellow halos around them. Late onset, the surface of the lesion grows a gray powder. When the disease is heavy, several lesions come together, often causing the leaves to dry off. The lesions on stems and petioles are oblong, dark brown and slightly sunken. The lesions of black spot are generally smaller than brown spot, with a diameter of 1-5 mm, a dark color, dark brown, and no halo around. After the onset of disease, the lesions on the back of the leaves had mildew-like black spots, and the black spots were arranged in a roulette pattern.
2. Infestation cycle Two leaf spot infection cycles are similar, and the pathogens overwinter on the stems and leaves of the diseased plants. The germs are spread by wind and seeds, and when the temperature is 22-23°C, the germs develop rapidly, and the spores of the germs are particularly produced during high temperatures and rain. Seeds and seed husks may also be accompanied by bacteria, germinating in the following year.
3. Prevention and control points (1) Selection of disease-resistant varieties. Generally, the direct-type varieties are more resistant to disease than the vine-type varieties. (2) Rotation for crop rotation: In areas where the incidence is heavy, crop rotations such as wheat, corn and sorghum should be carried out for 2-3 years. (3) Chemical control. Spray once every 7-10 days in the initial stage of disease. Available 1:2:150 Bordeaux mixture, or 50% carbendazim 1000-1500 times wettable powder or 75% chlorothalonil wettable powder 600-800 times. Or use 65% zein zinc WP 300-400 times to control.
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