How to prevent and control peanut leaf spot? These methods are very practical

1. Symptoms Peanut leaf spot disease mainly consists of black spot and brown spot, and both diseases mainly harm the leaves. When peanuts are affected, symptoms first appear on the lower leaves, then gradually spread to the upper leaves. In the early stage of the disease, small brown spots appear, which gradually develop into round or irregular lesions. Brown spot lesions are larger, with a yellow halo around the lesion, while black spot lesions are smaller, lighter in color than brown spot, with neat edges and no obvious halo. In humid weather or during prolonged rainy periods, the lesions can merge with each other into irregular large spots, and the leaves become scorched, seriously affecting photosynthesis. If it occurs on petioles, stems, or pegs, it may cause oval dark brown or brown lesions in mild cases, or the entire stem or peg may turn black and die in severe cases, causing a sharp decline in peanut yield.

2. Prevention and control (1) Eliminate the pathogen. After the peanut harvest, promptly remove the diseased plant residues left in the field, and do not throw them around or pile them up at will. Plots with diseased residues should be plowed in time to accelerate the decomposition of the diseased residues and prevent the pathogen from infecting peanuts again. (2) Select disease-resistant varieties. The more resistant ones are generally varieties with upright growth, thick leaves, dark color, and large peanut seeds, or early-maturing varieties. In plots with severe disease, these varieties can be selected for planting, such as Jihua No. 2, Luhua 14, etc. (3) Strengthen cultivation management. Sow at the appropriate time, plant at a reasonable density, apply sufficient base fertilizer, and topdress in time to promote vigorous growth of peanuts and improve disease resistance. (4) Chemical control. Spraying pesticides in time at the early stage of the disease can reduce the disease. Relatively good pesticides: 80% mancozeb 400x solution, 70% thiophanate-methyl 1000-1500x solution, 50% carbendazim 1000-1500x solution. When spraying, be careful to spray evenly and thoroughly, spray once every 7-10 days, and spray 2-3 times in succession, which can basically control the occurrence of the disease.