Characteristics and Control of Powdery Mildew of Astragalus

Astragalus is a wild or cultivated species and is a traditional Chinese medicinal material in Hebei Province. Astragalus is seriously affected by powdery mildew during the whole growing season and directly affects the yield and quality. 1. Symptoms: Aspergillus powdery mildew not only damages the leaves, but also damages the flower buds, pods, culms and other parts. The whole plant is covered with white powder, and the incidence of jaundice in the autumn reaches 100%. 2. Pathogens: Astragalus powdery mildew is caused by the infection of Eryaiphe pisiDC. The closed capsular shell is spherical or oblate spheroidal, dark brown, with several ascospores in the closed capsular shell. The ascospora is oval, colorless, and has a short handle. 3. Occurrence characteristics: After investigation, the powdery mildew of Astragalus membranaceus has formed a sexual generation in late September, and it is wintering with the ascoma fruit on the sick body. When the temperature reached above 20°C in May of the following year, the spores of the germs germinated, and the plants of the first-year jaundice were infected. The morbidity center of the disease began to grow. The diseased bacterium spreads and repeats infestation. The white powder appears on the leaves, spreads by the wind, and spreads quickly to neighboring plants. All fields were soon covered, and the disease was severe 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. 4. The occurrence and prevalence of powdery mildew in Astragalus is not closely related to temperature. The suitable temperature range for the spore germination of P. aeruginosa is 20°C-30°C. In the northern region of the year, the Huangtian field begins to occur from late May. The annual Huangqitian field begins to occur in late June. Until November, powdery mildew spreads in the fields. . 5. Field survey found that in addition to harming yellow peony, the yellow smut powdery mildew disease also damages wind (Umbelliferae), sand scorpion (legume), calendula, sign, flavescens, scutellaria, aster (Asteraceae). 6. Control methods: Agricultural control: Burnt stubble leaves to reduce the source of overwintering bacteria. According to the habit of the winter wheat aphid powdery mildew on litter, after harvesting the astragalus, the debris was removed and burned to reduce the source of overwintering bacteria. Chemical control: The occurrence of powdery mildew in Astragalus is relatively long, and it is the best time to prevent and treat A. alba powdery mildew from June to October. In the early, middle and late stages of the disease, each spray was sprayed once and sprayed with 25% triadimefon 4000 times. The control effect was over 90%. The survey found that the efficacy of triadimefon for up to 1 month, triadimefon ideal for powdery mildew pesticides. In addition, 70% thiophanate-methyl, 70% mancozeb 500-800 times spray control.

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