Simple Identification of Peanut Leaf Blight

There are many causes of peanut leaf blight, but it can be divided into two categories: infectious diseases and non-infectious diseases. Generally speaking, the latter is difficult to control with pesticides. The author has personally seen the scene of farmers using carbendazim to control peanuts after sunburn, which shows that the types of peanut leaf blight can not be correctly identified, which will inevitably affect the correct application of control techniques. After on-the-spot observation, the common symptoms of peanut leaf blight were briefly described. 1 non-infectious leaf blight 1) sunburn. It often occurs in summer, when the temperature suddenly rises to more than 35 ℃, which is easy to occur in dry and hot wind weather. The occurrence range is large, the area is wide, and it is often common in an area. For example, this phenomenon occurred in Linshu County in 1999. Observe a peanut, the leaves that are exposed to direct sunlight are dry, and the leaves that are out of direct sunlight behave normally. 2) waste gas pollution. Often after rain, the fields around chemical plants (especially phosphate fertilizer plants) and those far away from chemical plants behave normally. Observation of a pile of peanuts, old leaves, tender leaves, stems and other aboveground parts will show dry. It is generally caused by acid rain containing sulfur and fluorine. 3) Pesticide damage. It often occurs after pesticide application, because crops are sensitive to certain drugs and the concentration of the solution is too high in the process of controlling peanut diseases and insect pests. In addition, herbicide damage caused by herbicides is also common when sprayers that have been sprayed with herbicides are not cleaned. The injured fields were limited to the fields that had been treated, while the other fields with drugs behaved normally. (2) compared with non-infectious leaf blight, infectious leaf blight is not formed in a short time, but gradually formed. 1) Leaf spot. Including brown spot and black spot. What they have in common is that they all occur in the middle and later stages of peanut growth. It was mainly harmful to the leaves, and the lower old leaves first fell ill and gradually spread upward. The initial brown needle-sized spot gradually enlarged into a round spot. Under wet conditions, the disease spots produce grayish-brown mildew, and the disease spots become irregular spots, causing fallen leaves. 2) Peanut net spot. It is a disease that has been aggravated in recent years. There are two types, namely, speckle type and speckle type. The common feature is that under the condition of high humidity, small black spots appeared on the leaves at first, and then expanded into irregular black-brown disease spots with reticular edges, resulting in a large number of fallen leaves of peanuts in the middle and later stages. In addition, peanut root rot, stem rot, white silk disease, bacterial wilt and so on also lead to peanut leaf blight, often the whole plant withered. But these diseases generally occur less frequently.