Harm and control of brown spot of Angelica sinensis

The pathogen of Angelica brown spot (SeptoriaSP.) is a half-known fungus of the genus Cercospora. Conidia orbicular, conidia linear to needle-shaped, colorless, transparent, upright or slightly curved, most apical slightly pointed, 1 Mel 3 septum.

The main results are as follows: 1. the harmful symptom is harmful leaves. In the early stage of the disease, brown spots appeared on the leaf surface, the disease spot gradually expanded, a chlorotic halo appeared on the periphery, the edge was reddish brown, and the center was gray-white. In the later stage, small black particles appeared in the disease spot, and when the condition was serious, most of the leaves were reddish brown, and finally gradually withered and died.

2. Conidia are not tolerant to low temperature, germinate easily when wet, and die because there is no suitable host, so it is not the main source of overwintering bacteria. The pathogen mainly overwintered in the diseased and residual tissue by conidia, which produced conidia when the temperature was suitable in the second year, spread by wind and rain, and expanded the damage. When the spores fell on Angelica leaves, they germinated in dew drops or water, produced bud tubes, invaded by stomata, expanded and spread in the intercellular space of leaves, resulting in disease spots on leaves, conidia and re-infection. The disease began in late May, was more severe from July to August, and lasted until October. High temperature and humidity are beneficial to the disease.

3. Prevention and control measures ① should do a good job of pastoral cleaning in winter, completely burn down diseased and disabled tissues, and reduce the source of bacteria. The diseased leaves were removed in time at the initial stage of the onset of ②, and sprayed with Bordeaux solution of 1purl 150 or Dysen zinc 500 times 65% or methyl topiramate 800 times 1000 times 50% for prevention and treatment, once every 10 days or so for 3 consecutive 4 times. ③ established disease-free field and selected disease-free seeds. During the growing period of Angelica sinensis, ploughing and weeding should be carried out in time to prevent stagnant water in the field and reduce damage loss in rainy season.