Grape brown spot control method
Brown spot disease, also known as leaf spot, is caused by the fungal infection of Pseudocervella species, primarily affecting grape leaves. In the early stages of infection, small, light brown, irregularly shaped spots appear on the upper surface of the leaves. As the disease progresses, these spots grow larger, reaching up to 1 cm in diameter. The color of the lesions gradually changes from brownish to auburn, with a yellowish-green halo around the edges. In severe cases, the spots merge into large, well-defined areas, and the affected parts of the leaves become necrotic. On the underside of the leaves, the symptoms are less distinct, but the tissue eventually dies. During periods of heavy rainfall or high humidity, a brownish, moldy growth may develop on the infected areas.
To manage this disease effectively, several control measures can be implemented. First, it is important to remove all plant debris from the vineyard to reduce the source of infection. Before bud break, a 3–5° Brix lime sulfur solution can be applied as a preventive treatment. In regions where the disease is more prevalent, a combination of fungicides can be used for better control. For example, in June, spraying with a 1:1 ratio of 200-fold Bordeaux mixture is recommended. From July to September, alternating between 500-fold 50% carbendazim, 600–800-fold chlorothalonil, or 800–1000-fold 70% thiophanate methyl every 10–15 days can help suppress the disease. It's worth noting that 65% mancozeb may cause phytotoxicity on certain grape varieties, especially in northern regions, so the concentration should be adjusted to 1000–1200 times. Additionally, proper fertilization and pruning practices play a key role in disease prevention. Using balanced multi-element compound fertilizers can strengthen the vines, improve their resistance to diseases, and promote healthy growth. Pruning should be done regularly to ensure good air circulation and sunlight penetration throughout the canopy, which helps reduce the risk of fungal infections.
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