The most common diseases of osmanthus fragrans occur on leaves, including brown spot, Fusarium wilt and anthracnose. These diseases will lead to premature defoliation of osmanthus fragrans, weaken plant growth potential and reduce flower yield and ornamental value.

Brown spot of osmanthus fragrans

At the initial stage of the disease, there are yellow macules on the leaves, which gradually expand into a nearly round lesion with a diameter of 2 ~ 10mm, or become irregular lesions due to the expansion of the lesion restricted by veins. The focus is yellowish brown to grayish brown with yellow halo around it. Brown spot disease generally occurs from April to 10, and older leaves are more susceptible to disease than younger leaves. The pathogen overwinters on the diseased leaves with mycelium, and conidia are produced in the following spring for primary infection, and the conidia are spread by airflow and raindrops. Osmanthus wilt

The pathogen of the disease mostly invades from the leaf margin and tip, and occurs at the leaf margin and tip. At the initial stage of the disease, light brown spots are produced on the leaves, which gradually expand into round or irregular lesions, and then expand into nearly round or irregular taupe spots with dark brown edges. Fusarium wilt occurred from July to 165438+ 10, which can occur all year round in the greenhouse with poor environmental conditions. Pathogens are spread and infected by conidia through wind and water. High temperature, high humidity and poor ventilation are conducive to the onset. Old leaves and leaves at the lower part of the plant are seriously ill when the plant grows weak and overwinters.

Anthracnose of osmanthus fragrans

This disease infects the leaves of osmanthus fragrans. At the early stage of the disease, small chlorosis spots appeared on the leaves, which gradually expanded to form round, semi-circular or oval lesions. The lesion is light brown to grayish white with reddish-brown ring at the edge. Under wet conditions, pink myxospore discs appear on the lesion. Anthrax occurs from April to June. Pathogenic bacteria overwinter in the diseased leaves of maple trees and spread through wind and rain.

Preventive and control measures

First of all, reduce the source of infection. Thoroughly remove diseased leaves in autumn. Potted sweet-scented osmanthus should remove the diseased leaves in time. Secondly, strengthen cultivation management. Choose fertile and well-drained soil or substrate to plant osmanthus fragrans; Increase the application of organic fertilizer and potassium fertilizer; Planting density should be suitable for ventilation and light transmission, reduce leaf humidity and reduce diseases. Scientific use of chemicals for prevention and control. At the initial stage of the disease, the Bordeaux mixture can be sprayed at a ratio of 1: 2: 200, and then 50% carbendazim wettable powder at a ratio of 1000 or 50% benomyl wettable powder at a ratio of 1000 to 1500 can be sprayed. Seedlings in seriously ill areas should be soaked and disinfected with 1000 times potassium permanganate solution when they leave the nursery.