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Grape Cob Brown Blight and Its Control Techniques
Grape brown ear blight is a newly identified disease affecting grapevines, which has become increasingly severe in regions such as Liaoning, Shandong, and Hunan in recent years. In some vineyards of Liaoning, more than 50% of the plants are affected, with a yield loss ranging from 20% to 30%. This disease poses a serious threat to grape production and requires immediate attention.
Symptoms of the disease typically appear on young grape clusters. Initially, the branches and cobs of the young panicles turn brown, then gradually wither and dry out, turning dark brown. The affected parts may lose water rapidly, leading to wilting and dropping of the entire cluster. Under humid conditions, black moldy substances—composed of conidia and conidial stalks of the pathogen—may form on the surface of the infected areas. In later stages, the dried branches often fall off. On developing fruit, small, round, dark brown spots (about 2 mm in diameter) appear on the skin. These lesions remain limited to the epidermis and, as the fruit grows, develop into scab-like formations. However, they do not significantly affect fruit development. The disease can also infect the flower corolla when the flowers are open.
The occurrence of grape brown ear blight is heavily influenced by environmental conditions. The disease tends to be most severe between late April and May, during the flowering stage of grapevines, especially when low temperatures and heavy rainfall occur. Additionally, there are significant differences in resistance among grape varieties. Varieties such as Jufeng are highly susceptible, followed by Black Olin and Red Banana. Older vines tend to show more severe symptoms, while younger plants (2–3 years old) are less affected. Vineyards located in low-lying areas or surrounded by buildings experience higher disease incidence, whereas those in open, well-ventilated, and light-transmitting environments have lower rates. The disease is more prevalent in northern regions compared to southern ones.
Control measures are essential for managing this disease. Before bud break, spraying 3–5 degrees of lime sulfur or a 0.3% sodium pentachlorophenol solution can effectively eliminate overwintering pathogens and protect bud scales. During the pre- and post-flowering periods, applying 50% carbendazim wettable powder diluted 1000 times or thiophanate-methyl wettable powder at 500–800 times provides excellent control. In addition, proper orchard management, including reducing humidity and planting resistant varieties, can significantly reduce disease occurrence. These practices, combined with timely fungicide applications, are crucial for long-term disease management.