Peanuts beware of early defoliation

The main causes of early defoliation of peanut are as follows: the early defoliation and senescence of peanut, and the more serious in the sandy soil; the harm of leaf spot, especially black spot and brown spot, spreads rapidly once it occurs, often causing a large number of leaves to fall off within a few days; early and excessive spraying of regulators is especially more serious than long-term and paclobutrazol and regulators containing this component. Prevention of early defoliation can be aimed at different reasons, take corresponding measures, the main measures are: 1, prevention of leaf spot disease. Peanut leaf spot is mainly caused by black spot and brown spot, and 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 lighter than brown spot, 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. In the late growth stage of peanut, there are many kinds of leaf spot disease that harm leaves and cause early defoliation, and brown spot disease and net spot disease are the most serious and difficult to control. In the early stage of the disease, 80% mancozeb or Dasheng 600 × 800 times can be sprayed 3 times every 8 to 10 days, or 70% methyl topiramate 800 times 1000 times or other new fungicides can be sprayed. 2. Foliar spraying fertilizer. In the late growth stage of peanut, the ability of roots to absorb nutrients from soil and the ability of nodules to fix nitrogen began to decrease, while the ability of leaves to absorb nutrients was enhanced. Foliar fertilizer supplementation has many advantages, such as fast absorption, rapid action, high utilization rate, good return and so on. It is a better measure to prevent premature senility caused by early defoliation. Foliar topdressing is a fertilization method often used in production. This paper introduces the fertilizer suitable for foliar topdressing of peanut and its application method: 1% urea solution can be used for foliar spraying. Peanut leaves have a strong ability to absorb phosphorus. In the middle and later stages of its growth, 60kg was sprayed once every 7-10 days with 2%-3% superphosphate extract every 667 square meters, which could accelerate the transport of photosynthate to pods. Potassium dihydrogen phosphate. Use 150g potassium dihydrogen phosphate 200g per 667m2, spray water 50kg in the evening or cloudy afternoon after being fully dissolved, preferably three times at an interval of 7 days; if it rains within 8 hours after spraying, re-spray it once, which can increase production by 18.2% to 26.9%. The application of iron fertilizer to iron deficient soil can increase the yield by more than 10%. Generally, 0.2% ferrous sulfate solution is sprayed once every 5-6 days for 2 times in a row during the flowering stage, podding stage or iron deficiency symptoms of peanut plants.