Pay attention to control of peanut leaf spot
After the beginning of autumn, peanuts will enter the end of the harvest. This stage is the key period for the formation of output, and it is also prone to cause various diseases. Peanut leaf spot, in particular, is more common and is an important disease in the later stage of peanut production.
I. Disease characteristics
Peanut leaf spot includes brown spot, black spot and focal spot disease. After the onset of peanuts, the leaves are covered with scars and fall off prematurely, which seriously affects the photosynthetic efficiency and makes the pods less full, which reduces the yield and quality.
1. Brown spot. At the early stage of disease, lesions of yellow-brown or rust-colored needles are formed on the leaf blade first, and then gradually expand to form lesions ranging in size from 4 to 10 mm in diameter. They are nearly round or irregular in shape and have a light brown or dark brown surface. There is a clear yellow halo around the edge. In severe cases, several lesions are connected together, causing the leaves to dry off. In moist conditions, gray molds were produced on the old lesions (fronts of leaves), irregularly arranged, and lesions on stems, petioles, and stipules were oblong, dark brown, and slightly sunken in the middle.
2. Black spot. At the early stage of disease, the symptoms of the leaves are indistinguishable from those of the brown spot. The late lesions are mostly round or near-circular, with a diameter of 1-5 mm. They are dark brown or black. The yellow halos around the lesions are not obvious. They are on the back of old lesions. , There are many black dots, arranged in a concentric ring pattern, in the wet case, the lesions grow a layer of gray-brown mold. When the disease is severe, many lesions can be produced on each leaf, and they are connected to each other in an irregularly shaped large spot with a large number of leaves falling off, leaving only a few leaves at the top of the head. Oval-shaped black lesions can also be produced on the petiole and stem, and the stem becomes black and dead when severe.
3. Focus spot disease. The disease mostly occurs from the edge of peanuts, and the lesions after infection have a "V" shape. The lesions are large and appear black. Severe leaves can cause wilting, dryness, and shedding.
Second, prevention and control measures
1. Spray leaf fertilizer. For sandy lands with insufficient fertility, foliar fertilizers should be sprayed in time when the peanuts enter the pod-logging stage, which can be combined with insecticides and fungicides. Generally, 250 grams of urea and 150 grams of potassium dihydrogen phosphate are used per acre, sprayed on 30 kilograms of water, sprayed once every 7 days, and continuously sprayed 2-3 times.
2. Scientific medication. In the early stage of disease, when the diseased leaf rate reaches 10% to 15%, the pesticide application starts. Use 50% carbendazim WP 1000 times, or 70% thiophanate-methyl WP 1500 times, or 75% 100%. Bacterial WP 600 times liquid spray control, spray once every 7-10 days, even spray 2-3 times.
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