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How to prevent and control powdery mildew on Japanese euonymus? These methods you need to know

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Symptoms: The disease affects leaves and twigs. The lesions are mostly distributed on the upper surface of the leaves. In the early stage of the disease, many small white round spots are scattered on the infected leaves. As the lesions gradually expand and merge with each other, they become irregular large spots. When the disease occurs severely, the infection rate of new shoots can reach 10%. White powder appears on the entire surface of the leaves and new shoots. The diseased leaves gradually lose green, turn yellow, and finally turn brown-black. The diseased parts become deformed, the diseased leaves shrink, and the diseased shoots twist and wither. Pathogen: The pathogen is Oidium euonymi (Are.) Sa

Symptoms: The disease affects leaves and twigs. The lesions are mostly distributed on the upper surface of the leaves. In the early stage of the disease, many small white round spots are scattered on the infected leaves. As the lesions gradually expand and merge with each other, they become irregular large spots. When the disease occurs severely, the infection rate of new shoots can reach 10%. White powder appears on the entire surface of the leaves and new shoots. The diseased leaves gradually lose green, turn yellow, and finally turn brown-black. The diseased parts become deformed, the diseased leaves shrink, and the diseased shoots twist and wither.

Pathogen: The pathogen is Oidium euonymi (Are.) Sacc., belonging to the Deuteromycotina, Hyphomycetes, Moniliales, genus Oidium.

Occurrence pattern: The pathogen overwinters as mycelium in the diseased plant body. In the following spring, the pathogen produces a large number of conidia, which are spread by airflow and cause infection. Conidia can be produced repeatedly for reinfection. The pathogen parasitizes the surface of the host branches and leaves and produces haustoria that penetrate into epidermal cells to absorb nutrients. High summer temperatures are not conducive to the development of the disease. Plants planted under tree shade are severely affected, while adjacent plants facing the sun are less affected or not affected. Young leaves and new shoots are severely affected, while old leaves are lightly affected.

Control: 1. Reduce sources of infection: In winter, remove fallen leaves and diseased shoots and destroy them in a centralized manner. 2. Chemical control: In the early stage of the disease, spray 25% triadimefon wettable powder at 1500-2000 times dilution, or 70% thiophanate wettable powder at 800-1000 times dilution, or 0.3-0.5 degree Baume lime sulfur mixture, or 50% Tuzet wettable powder at 800 times dilution, once every 10-15 days, spraying 2-3 times.

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