Symptoms and Control techniques of Peanut Leaf spot

Peanut leaf spot is the general name of peanut black spot, brown spot, net spot and scorch spot, which is an important disease on peanut, which has a great influence on the yield and quality of peanut. The main symptoms of peanut leaf spot are black spot and brown spot. Compared with brown spot, black spot has a wide range of diseases and serious harm. The two diseases are mainly harmful to leaves. During the onset of peanut disease, symptoms began to appear in the lower leaves, and then gradually spread to the upper leaves, producing brown spots in the early stage of the disease, and gradually developed into round or irregular disease spots. The spot of brown spot is larger, there is a yellow halo around the spot, while the spot of black spot is smaller, the color is smaller, the edge is neat, and there is no obvious halo. The weather is humid or long-term overcast and rainy, disease spots can be combined with each other into irregular spots, leaves scorched, seriously affecting photosynthesis. If it occurs on the petiole, stem or fruit needle, it will produce oval black-brown or brown disease spots, and if it is heavy, the whole stem or fruit needle will blacken and die, resulting in a great decrease in peanut yield. Second, the control methods are basically the same because the two diseases are caused by semi-known subphylum fungi. Prevention and control should be based on agricultural control, eliminate the initial pathogens, and then carry out chemical control when necessary. In addition, attention should be paid to the selection of disease-resistant varieties. (1) to eliminate the source of the disease. Remove the germ remains left in the field in time after peanut harvest, and don't litter or pile up at will. Plots with bacterial residues should be ploughed in time to accelerate the decomposition of bacterial residues, and peanut seedlings in the field should be treated before planting flowers to prevent pathogens from infecting peanuts. It is better to rotate peanuts with corn and rice. (2) selecting disease-resistant varieties. The varieties that are more resistant to disease are generally varieties with erect growth, thick leaves, dark color, large peanut grains or early-maturing varieties, which can be planted in the seriously affected plots. (3) strengthen cultivation management. Sowing at the right time, reasonable close planting, applying sufficient base fertilizer and topdressing in time, so as to promote the robust growth of peanuts and improve disease resistance. (4) Chemical prevention and control. Timely spraying and control in the early stage of the disease can reduce the disease. Better agents: 80% Dysen zinc 400 times solution, 70% methyl thiophanate 1000-1500 times solution, 50% carbendazim 1000-1500 solution. When spraying, pay attention to spray evenly, spray thoroughly, if 0.1 kg of soybean powder or washing powder is added to every 50 kg solution, the control effect will be better; spraying once every 10-15 days, even 2-3 times, can basically control the occurrence of the disease.