Symptoms and control methods of burdock black spot

Arctium lappa L. alias Yaksha head, rat sticky grass, old sow ears. Compositae is a perennial herb. The fruit is used as medicine. Roots can also be used as medicine. It has the effects of dispersing wind-heat, dispersing lung, penetrating rash, resolving masses and detoxifying. It is cultivated throughout the country.

Symptoms burdock black spot occurs mostly in autumn, and the damage to seedlings is serious. It mainly damages leaves and petioles. At seedling stage, brown to tawny round spots, 2-20mm in size, smooth surface, thin spots in the middle and fade to light brown to gray, easy to rupture or perforate, scattered black dots, i.e. conidia. In severe cases, multiple lesions merge into irregular shapes.

Phyllosticta lappae Sacc. is a fungus belonging to the subphylum Semi-fungi. Conidia pale brown, spherical to oblate, 75-1385μm in size, buried in tissue, with orifice at tip; conidia colorless, single cell, elliptic to long ellipsoid, rounded at both ends, 5.5-6.1×4-5 (μm) in size, mostly with 1 septum.

Pathway of transmission and condition of infection The pathogen overwinters on diseased leaves as conidia, and then produces conidia to spread by wind and rain in the following year, and carries out primary infection and secondary infection. The temperature is 25-27℃, the disease is easy to occur after rain, and the disease spots become perforated due to rainfall.

control methods

(1) After harvest, the sick and disabled bodies shall be removed in time and buried or burned in a centralized manner.

(2) Soak the seeds in warm water at 40-50℃ for 3 hours before sowing, rinse the seeds, wrap them with wet gauze, and place them at 25℃ for germination. The germination rate of seeds is higher than 85%, so as to make the seedlings grow healthily and reduce the disease at seedling stage.

(3) In areas with severe disease or in autumn, deep ploughing shall be carried out in time to bury the bacteria in the soil.

(4) Rotation with other crops for more than 3 years.

(5) Appropriate planting density, improve ventilation and light transmission conditions of burdock field.

(6) Spraying 400 times solution of 30% Lvdebao suspension agent or 500 times solution of 50% Baijuntong wettable powder, 300 times solution of 14% ammonia copper solution and 500 times solution of 77% coccidin wettable particle powder during seedling stage. Every 10 days or so, spray 50-60L of the right solution every 667m2. Control 2-3 times. The drug was stopped 3 days before harvest.