What are the symptoms of Osmanthus brown leaf spot?
The pathogen of Osmanthus brown leaf spot is Cercospora osmanthicola. It commonly occurs in Hangzhou and other places. Osmanthus brown leaf spot is a very common disease, mainly infecting leaves; in severe cases it causes the whole plant to defoliate, affecting flowering and ornamental value. It commonly occurs in Hangzhou and other places. Symptom characteristics: affected leaves first show small yellow spots, which then gradually turn yellow-brown to...
The pathogen of Osmanthus brown leaf spot is Cercospora osmanthicola. It commonly occurs in Hangzhou and other places. Osmanthus brown leaf spot is a very common disease, mainly infecting leaves; in severe cases it causes the whole plant to defoliate, affecting flowering and ornamental value. It commonly occurs in Hangzhou and other places.
Symptom characteristics: affected leaves first show small yellow spots, which then gradually turn yellow-brown to gray-brown. The spots are nearly round or irregular in shape, or appear as angular spots when their expansion is restricted by leaf veins. The spots are 2~10 mm in diameter and have a yellow halo around them. In humid weather, the diseased parts produce black moldy dots, which are the pathogen's conidiophores and conidia.
Disease development pattern: the Osmanthus brown leaf spot pathogen overwinters as mycelium on diseased plants and fallen diseased leaves, becoming the source of primary infection the following year. In late March each year, it produces conidia and begins primary infection. The conidia are spread by airflow and raindrops and can invade directly or through wounds and natural openings. Old leaves are more susceptible than young leaves. Brown leaf spot occurs from April to October, and the disease subsides after November. High temperature and high humidity favor the disease. Resistance varies among cultivars; generally, Dangui is more resistant than Jingui and Yingui.
Control methods: (1) In winter, prune to remove diseased leaves and clear away fallen diseased leaves, and burn them in a centralized manner; (2) in early May, spray Bordeaux mixture at 1:2:100~200, after which 50% benomyl 1000 to 1500 times solution, or pyrazophos 500 times solution, or 70% thiophanate-methyl 1000 times solution may be sprayed.
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