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Symptoms and Control Methods of Leaf Blight in Hybrid Magnolia

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The main symptoms occur on the leaves, and in severe cases can spread to the petioles and flower buds. The lesions mostly occur at the leaf margins. In the early stage, they are chlorotic yellow spots, water-soaked in appearance. Numerous lesions merge into patches, expanding outward in a fan shape, with dark brown edges and grayish-yellow centers, which can cause early defoliation. In humid environments, black-gray granular bodies appear on the fallen leaves. Causes of the disease: This disease is a fungal disease; the pathogen survives in leaf buds and on diseased plant residues, spreads via air currents, and can directly infect and damage through the stomata of leaves that are weak in growth or physiologically injured. Injured plants and environmental conditions with high wind speed

The main symptoms occur on the leaves, and in severe cases can spread to the petioles and flower buds. The lesions mostly occur at the leaf margins. In the early stage, they are chlorotic yellow spots, water-soaked in appearance. Numerous lesions merge into patches, expanding outward in a fan shape, with dark brown edges and grayish-yellow centers, which can cause early defoliation. In humid environments, black-gray granular bodies appear on the fallen leaves.

Causes of the disease: This disease is a fungal disease; the pathogen survives in leaf buds and on diseased plant residues, spreads via air currents, and can directly infect and damage through the stomata of leaves that are weak in growth or physiologically injured. Injured plants and environmental conditions with high wind speed and low air humidity are conducive to the occurrence of the disease, and the disease is severe under high-temperature and dry environments.

Control methods: When the flower buds and leaf buds have not yet opened, spray the branches and trunk with 3 to 5 degrees Baumé lime sulfur mixture. Where conditions permit, windbreaks (wind protection facilities) can be set up in winter to prevent physiological diseases. In spring, increase foliar water spraying to improve the air humidity of the micro-environment. In the early stage of the disease, spray chlorothalonil and carbendazim fungicides at 800 times dilution.

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