The main reasons for the early fall of peanuts are as follows: defertilization and premature aging, and severe sand masses are more serious; leaf spot disease, especially black spot and brown spot disease, will spread rapidly once they occur, causing massive leaf shedding; premature or Excessive spraying of plant regulators, in particular, is more serious than P. paclobutrazol and regulators containing this component.
The preventive measures are as follows:
1. Peanut leaf spot. Mainly black spot and brown spot disease are the main diseases, and both diseases are mainly damaged leaves. When the onset of peanuts, the symptoms began to appear from the lower leaves of the plants, then gradually spread to the upper leaves, brown spots in the early stages of the disease, and gradually developed into round or irregular lesions. The brown spot is larger, yellow halos surround the lesions, while the black spot is smaller, the color is lighter than the brown spot, and the edges are neat, with no obvious halos. The weather is humid or long-term rainy, the lesions can be combined with each other into irregular large spots, the leaves scorch, seriously affecting photosynthesis. If it occurs on the petiole, stalk or fruit needle, it will produce oval dark brown or brown lesions. If it is heavy, the entire stem or fruit needle will turn black and die, causing the peanut production to drop significantly. In the late growth period of peanut, there are many kinds of leaf spot that damage the leaves caused by early defoliation. The most serious and difficult to control is the brown spot and net spot disease. In the early stage of the disease, 80% mancozeb or 600 to 800 times liquid can be sprayed, and 70% thiophanate-methyl 800 to 1000 times liquid or other novel bactericide can be sprayed. Spray once every 8 to 10 days, spraying 3 to 4 times continuously.
2. In the late growth stage of peanut, the ability of the root system to absorb nutrients and nodule nitrogen from the soil began to weaken, but the ability of the leaves to absorb nutrients was increasing. Foliar spray fertilizer supplement has many advantages such as rapid absorption, rapid action, and high utilization rate. It is a good measure to prevent early decending caused by premature senescence. Foliar spraying can be performed with 1% urea solution. In the middle and late stages of peanut growth, the application of 2% to 3% of superphosphate calcium leaching solution 60 kg, spray once every 7 to 10 days, and even spray 2 to 3 times. Or spray potassium dihydrogen phosphate 75 ~ 100 kg, 50 kg of water, to be fully dissolved in the evening or cloudy afternoon spray, it is best to spray three times, each interval of 7 days, if within 8 hours after spraying In case of rain, re-spray 1 time. In iron-depleted soil peanut field, 0.2% ferrous sulfate solution can be sprayed every 5 to 6 days, and sprayed continuously for 2 to 3 times during the peanut flowering stage, the pod stage or the iron deficiency symptoms of plants. .
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