Occurrence and Control of Powdery Mildew in Astragalus

Astragalus membranaceus is severely affected by powdery mildew throughout the growing season, directly affecting yield and quality.

Symptoms of smut powdery mildew not only harm the leaves, but also harm the stamens, pods, stems and other parts. In the early stages of the development of powdery mildew in Astragalus, sparse white powdery mildew layer was produced in leaves and capsules. At the later stage of disease, the white powder was pale and the leaves were yellow, and many small black spots appeared on the diseased leaves.

Pathogen Astragalus powdery mildew is caused by the powdery mildew infection of pea powdery mildew. Closed capsule spherical or oblate spherical, dark brown, several capsules in the closed capsule, oval ascaria, obovate, colorless, short handle.

Characteristics of the investigation After investigation, the powdery mildew of Astragalus membranaceus developed into a sexual generation in late September, and the fruit of the ascoma was overwintering on the sickly body. When the temperature reached 20 degrees Celsius in May the following year, the spores of germs germinated, and the plants of the two-year-old Astragalus membranaceus were infected first. The center of the disease occurred. The pathogenic bacteria proliferated, repeated infections occurred, white powdery substances appeared on the leaves, spread by the wind, and spread rapidly to neighboring plants. The field was soon covered, and the disease was serious from August to September. The prevalence and severity all reached 100%. From the end of September to the beginning of October, the fruit of the ascoma was formed and fell into the soil as the sick body overwintered. The first occurrence of the disease center in the field, and then spread to the surrounding disease, is the characteristics of the disease.

Control methods 1. Agricultural control: Burnt stubble leaves and reduce the source of overwintering bacteria. According to the habit of the winter wheat aphid powdery mildew on litter, after harvesting the aerial part of the astragalus, the debris was cleaned up and concentrated to burn down the source of overwintering bacteria. 2. Chemical control: The occurrence of powdery mildew in Astragalus is longer, and it is the best period to prevent and treat A. alba powdery mildew from June to October. Spray 50% thiophanate or 50% carbendazim 800-1000 times in the initial stage of disease, once every 10 days, 2 or 3 times in succession. In the middle and later stages, each spray was sprayed with 25% triadimefon 4000 times liquid and the control effect was over 90%. In addition, the use of 70% WP WP, 70% mancozeb wettable powder 500 ~ 800 times spray control.

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