Causes of broad bean brown spot disease

Humidity: During the growth of broad beans, if they encounter continuous rainy weather, they are susceptible to red spot disease.

Soil: Compared with sandy soil, the incidence rate will be higher in clayey soil.

Terrain: Farmland with low terrain has a higher chance of red spot disease than farmland with normal height.

Drainage: Farmland with poor drainage or plots with continuous cropping all year round are more susceptible to red spot disease.

Chloasma of broad bean is a bacterium of the subphylum Deuteromycota. It mainly damages broad bean crops, and its locations are leaves, stems and pods. After infection, the leaves initially show small auburn spots, and then expand into annular or oval lesions, with particularly obvious auburn edges. The middle of the lesions fade to grayish brown, with a diameter of 3 to 8 mm, and are densely covered with black spots arranged in a wheel pattern. , when the disease is severe, they merge into large irregular patches. When the humidity is high, the diseased parts will burst, perforate or die.

Symptoms of broad bean brown spot disease

Infected stems produce relatively large oval spots, with a diameter of 5 to 15 mm, a grayish-white slightly dented center, and a reddish-brown edge. The infected stems often wither and break. . The diseased spots on the pods are brown and black with black edges and dents around them. Severe pods wither, and the seeds are thin and immature. The bacteria can penetrate the pod skin and damage the seeds, causing dark brown or black stains on the surface of the seeds. The diseased parts of the stem pods also have black hard spots, which are pycnidia.

Shape characteristics of faba bean brown spot

The pycnidia are spherical, with a diameter of 90-100pm. Conidia are oblong or ovate, 12 to 15 × 4 to 5 (um) in size, with one septum. The pathogen prefers temperatures of 20 to 26°C, 35°C, and 8°C for growth. This bacterium only infects broad beans.

The transmission route of broad bean brown spot disease

The fungus spends the winter in seeds or diseased bodies, or uses pycnidia on broad beans to become the source of infection in the beginning of the second year. Conidia spread by wind and rain.

Criteria for the incidence of broad bean brown spot disease

The seeds have not been disinfected during production or base fertilizers have been applied, or the disease has been serious when planted too early or in wet areas.

What medicine is used for broad bean brown spot?

Chloasma of broad bean mainly damages leaves, stems and pods. After the leaves are damaged, they gradually become smaller in russet color, and then expand into oval lesions, with obvious russet color on the periphery and dark brown in the middle. Black particles arranged in a ring shape are densely grown on them. When the disease is severe, the lesions converge into irregularly large lesions. Spots, when wet and cold, the diseased parts will crack, break, or wither.

After the stem is damaged, it will cause large oval spots with a grayish-white slightly dented center, and reddish-brown edges, which are easy to wither and break. After the pods are damaged, they will develop sunken brown-black lesions with black surroundings. When the disease is severe, the pods will wither and the seeds will become thin and immature. After the pathogen penetrates the pod skin and damages the seeds, dark brown spots appear on the surface of the seeds. Broad bean brown spot is a disease caused by bacteria. The bacteria overwinter in the seeds or diseased bodies and become the source of infection early in the second year. Conidia spread by wind and rain. The seeds are not sterilized, the base fertilizer is applied, the seeds are planted too early, and the seeds are planted in wet areas to get the disease.

Main prevention and control methods

① Use disease-free pods. Before planting, soak the seeds in warm water at 56°C for 5 minutes to disinfect the seeds.

② Plant appropriately, not too early, plant in high borders, plant moderately sparsely, fertilize effectively, apply potassium fertilizer to improve disease resistance.

③Drug prevention and treatment. In the early stage of the disease, spray 47 Garenon wettable powder 600 times the liquid, 80 dasheng manganese zinc wettable powder 500-600 times the liquid, 80 spray gram wettable powder 600 times the liquid, 14 hydroxylamine copper liquid 300 times the liquid, 77 can kill Get wettable granules 500 times liquid, once every 10 days, prevent and treat 1-2 times.