Bean powdery mildew mainly attacks cowpeas, peas, broad beans, lentils, kidney beans, cabbage, celery, tomatoes and other vegetables. The disease is common in southern vegetable growing areas, and it has a great impact on yield when the disease is severe.
Bean powdery mildew mainly harms leaves and can also invade stems and pods. In the early stage of the leaf, a round yellow-brown small spot is formed on the back surface, and then expanded into an irregular purple or brown spot, and a white powdery mildew layer is formed on the leaf back or the leaf surface; Gray-brown, black dots between the layers of mildew. When the occurrence is serious, multiple lesions are connected to each other, and spread along the veins into a powder belt. The leaf surface also has lesions, and the color changes from white to grayish white to purple-brown, and the whole leaves are repeated, and finally the leaves are quickly yellowed off. Stems and pods are infected, producing a white powdery layer that allows the stems to dry up and the pods to shrink.
The pathogen is warm and humid, and the suitable temperature range is 15-35 °C. The most suitable climatic conditions are temperature 20-30 ° C and relative humidity 40-95%. The optimum growth period of crops is in the middle and late stages of flowering and pod-forming, and the incubation period is 3-7 days.
The main onset of legume powdery mildew is from May to November. The temperature is high, the rainy year is heavy, the dry and wet alternate or the temperature difference between day and night is large, and the nighttime leaf surface is prone to condensation. The weather is heavy, many years of continuous cropping, low terrain, poor drainage, over-planting, poor ventilation and poor growth. The field is seriously affected.
Control method:
(1) Select varieties with strong resistance; sorghum cultivation, reasonable close planting, ditch drainage, increase of phosphorus and potassium fertilizers to enhance plant growth and improve disease resistance; timely kill old diseased leaves, timely remove diseased bodies after harvest Take it out of the field for centralized destruction and reduce the source of bacteria in the field. In the protected area cultivation, it is necessary to strengthen ventilation and ventilation.
(2) Prevention and treatment of pesticide fungicides . Bean powdery mildew: In the initial stage of the disease, spray 25% acetaminophen suspension with 1000 times solution, spray once every 5-7 days, and continuously control 2-3 times.
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