There are many causes of peanut blight, but there are two major categories of invasive diseases and non-invasive diseases. In general, the latter is difficult to control with pesticides. The author once saw the farmers' use of carbendazim in the prevention of sunburned peanuts. This shows that the type of peanut leaf blight cannot be correctly identified and will inevitably affect the correct application of prevention and control technologies. After field observation, a brief description of the common symptoms of peanut leaf blight was made. 1 Non-infectious leaf blight 1) Sunburn. It often occurs in summer, when the temperature suddenly rises above 35°C, and it is prone to happen when hot dry weather occurs. The occurrence of a large area and a wide area is often a common occurrence in an area. Such as happened in Linyi County in 1999. Observe a pile of peanuts, the leaves that are exposed to direct sunlight are dry, and the leaves that are not directly exposed to sunlight are normal. 2) Exhaust gas pollution. It often happens after rainfall that the blocks surrounding the chemical plant (especially the phosphate fertilizer plant) and the blocks far from the chemical plant perform normally. Observed a pier of peanuts, old leaves, leaves, stems and other parts of the ground will show dry and dry. It is generally formed by the acid rain containing sulfur and fluorine. 3) Pesticide damage. Often occurs after the application of pesticides, due to the process of peanut pests and diseases, the crop is sensitive to a drug, caused by high concentrations of liquid medicine. In addition, sprays sprayed with herbicides are not cleaned and the phytotoxicity caused by herbicides is also common. The victimized fields are limited to fields where drugs have been used, while other fields that use drugs have performed normally. 2 Infectious leaf blight, compared with non-infectious leaf blight, is not a success in a short time, but gradually formed. 1) Leaf spot. Including brown spot and black spot. The common point is that both occur in the middle and late stages of peanut growth. The main damage to the leaves, the first old leaf disease, gradually spread upward. The lesions of the size of the first brown needle gradually expanded to round lesions. In moist conditions, the lesions produce tan-brown moldy, and the lesions become irregular large spots, causing defoliation. 2) Peanut net spot. It is a disease that has been aggravated in recent years. There are two types of web type and stain type. The common feature is that in the condition of high humidity, the initial blackish-brown spots appear on the leaves, and the dark brown irregular spots that expand to the edge of the net afterwards, causing large amounts of deciduous peanuts in the middle and later stages. In addition, peanut root rot, stalk rot, blight, and bacterial wilt also cause the peanuts to dry up and often the entire plant dies. However, these diseases generally occur lighter.
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