According to the China Pesticide Network , there are two main reasons for the early defoliation of peanuts: on the one hand, because of premature aging, the area with large sandy soil is more serious; on the other hand, it is caused by leaf spot disease, especially black spot and brown. Spot disease, spreading very fast, will cause a large number of leaves to fall off in a few days; premature and excessive spraying of plant growth regulators, especially longer than the long-term and paclobutrazol and containing this component-based regulator more serious. Take preventive measures to prevent early leaves.
First, the foliar sprayed peanuts reached the late growth stage, the ability of roots to absorb nutrients from the soil and the ability of the nodules to fix nitrogen began to weaken, while the ability of the leaves to absorb nutrients was enhanced. Foliar spray fertilizer supplement nutrients have many advantages such as fast absorption, rapid action and high utilization rate. It is a good measure to prevent premature aging and cause early leaves. The soil is sandy, the soil is thin, the base fertilizer is insufficient, the plant is short, the growth is weak, and the leaf yellowing has the phenomenon of de-fertilization. The 1% urea solution can be used for foliar spraying. Miaowang Zhujian has a field with a strong tendency to grow, and it is not necessary to spray urea. Peanut leaves have a strong ability to absorb phosphorus. In the middle and late stages of growth, pesticide manufacturers recommend spraying 2%-3% of superphosphate leaching solution per acre (immersion 14-16 hours of filtration) 60 kg, every 7-10 days. Spray once, even spray 2-3 times, generally increase production by 7%-10%. Or use 100-150 grams of potassium dihydrogen phosphate per acre, 50 kilograms of water, spray it in the evening or cloudy afternoon after it is fully dissolved, preferably spray 3 times, every 7 days, if within 8 hours after spraying In case of rain, it is necessary to spray again. Peanut is extremely sensitive to iron. It is planted on alkaline soil and is prone to iron deficiency. It shows symptoms of yellow leaves and whitening. If iron fertilizer is sprayed in time, it can turn green after a few days. It can be sprayed once every 5-6 days with 0.2% ferrous sulfate solution, and sprayed 2-3 times continuously.
Second, strict prevention of leaf spot disease Peanut leaf spot disease is mainly caused by black spot and brown spot disease, both of which are dominated by harmful leaves. When peanuts develop, symptoms begin to appear from the lower leaves, and then gradually spread to the upper leaves. In the early stage of the disease, brown spots are produced, which gradually develop into round or irregular lesions. Brown spot disease lesions are large, there are yellow halos around the lesions, while black spot disease lesions are smaller, the color is lighter than brown spot disease, the edges are neat, and there is no obvious halo. The weather is wet or long-term rainy, the lesions can be combined into irregular large spots, and the leaves are scorched, which seriously affects photosynthesis. If it occurs on the petiole, stem or fruit needle, it will produce an elliptical dark brown or brown lesion, but the whole stem or fruit needle will be black and dead, which will greatly reduce the peanut yield. From the peanut to the late growth stage, there are many kinds of leaf spot diseases that cause early leaves to cause damage to the leaves. The main damage is brown spot and net spot disease. It can be sprayed in time at the beginning of the disease. The better agents are: 80% of mancozeb 800 times solution, 70% methyl thiophanate 800-1000 times solution, agricultural anti-120 water 200 times solution, 50% colloidal sulfur 200 times solution, 1:2: 200 times Bordeaux mixture. When spraying, pay attention to spray evenly and spray thoroughly to prevent leakage. Spray once every 8-10 days, even spray 3-4 times, which can basically control the occurrence of the disease.
The pesticide network reminds everyone that when using pesticides for prevention and treatment, it is necessary to pay attention to the amount of drugs. It is necessary to get rid of the misunderstandings with more effects and avoid the occurrence of safety accidents caused by phytotoxicity.
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