Control of Leaf spot of Platycodon grandiflorum

Platycodon grandiflorum is a perennial herbaceous medicinal plant, which is used as medicine by its roots. The control method of Platycodon grandiflorum leaf spot disease is as follows:

1. Symptom identification: This kind of disease mainly harms the leaves of Platycodon grandiflorum. (1) White round or nearly round spots, 2-5 mm in diameter, appear on both sides of leaves when infected by leaf spot blight. In the later stage, the lesion was restricted by vein and showed polygonal shape, and many small black spots were produced on the lesion. The disease spots often converge with each other, causing the leaves to die. (2) When infected by P. verticillata, the leaf spots were bigger and round. 5-10 mm in diam., brown, with concentric whorls, bearing many small black spots. (3) When infected by anthracnose, discolored spots appeared on leaves at the initial stage of disease, gradually expanded to stems and branches, rough epidermis, dark brown, and contracted and depressed at the later stage. Under the condition of heavy rain and high temperature, the disease spots were water-soaked, and the stems and leaves of the plants withered in the later stage.

2. Pathogenesis rule: A large number of new conidia were produced by the diseased spots during the growth period of Platycodon grandiflorum, which were transmitted by wind and rain for many times, resulting in epidemic diseases in the field. Generally, the damage is serious in July and August. High temperature, rainy and foggy weather conditions, extensive management and poor growth are conducive to disease onset and epidemic, if the control is not effective, often lead to a large number of dead leaves.

3. Control techniques: (1) Improve plant disease resistance, strengthen field management, rationally plant close, pay attention to timely drainage and humidity reduction after rain. (2) Chemical control: spray 1:1:100 Bordeaux mixture or 600 times solution that can kill 2000 before disease; spray the following chemicals according to the disease type: 80% Dasheng 600 times solution, 50% mancozeb 500 times solution, 50% thiophanate-methyl 600 times solution, 50% carbendazim 600 times solution. If anthrax is serious, spray with 800 times 25% Spock. Spray carefully and carefully, depending on the progress of the disease and weather conditions, spray 2-3 times continuously, spray once every 7-15 days.