Downy mildew is a serious fungal disease that primarily affects grapevines, causing significant damage to leaves and often leading to excessive leaf drop. In addition to the leaves, the pathogen can also infect young shoots, flower clusters, and developing fruit, resulting in stunted growth, deformation, and even death of the affected parts. Severe infections may cause the tips of the shoots to die, leading to premature fruit loss. This not only reduces the current year’s yield but also weakens the vine, making it more susceptible to winter damage, which can negatively impact production in the following season.
To address this issue, researchers from the Division of Plant Protection at the Yantai Academy of Agricultural Sciences in Shandong Province, including Dr. Shu Ding, conducted field trials to evaluate the effectiveness of several fungicides against downy mildew. Among the tested products was Baitai (60% pyraclostrobin-Senson water-dispersible granules), along with four other fungicides: Product-run (70% dextrose dry suspension), Kairun (25% pyrazophos emulsifiable concentrate), Kelu (72% copper oxychloride wettable powder), and 80% phosphoramide aluminum wettable powder.
The trial was carried out in vineyards heavily infected with downy mildew. Each treatment was applied at specified dilutions—Baitai at 1,500 times, Product-run at 700 times, Kairun at 3,000 times, Kelu at 700 times, and phosphoramide aluminum at 500 times—every 10 days for a total of three applications. A control group was treated with plain water.
Results showed that in the untreated plots, the disease progressed rapidly, with increasing leaf infection rates and visible mold on the underside of the leaves. The leaves became scorched and eventually fell off. In contrast, all five fungicides significantly improved plant health and reduced disease severity. Seven days after the second application, Kairun demonstrated the highest efficacy at 93.83%, far surpassing the other treatments. By the time of the third application, all treatments had an efficacy rate above 81.26%. Notably, Baitai achieved an impressive 98.15% and 97.38% control effect, outperforming both Kelu and phosphoramide aluminum.
Overall, Baitai and Kairun proved to be highly effective in controlling downy mildew. While Kelu and phosphoramide aluminum showed slightly lower efficacy (over 88%), they still offered good protection. These four fungicides can serve as effective tools for managing the disease in vineyards. However, Jinrun (Product-run) had a lower control rate of only 81.26%, making it less suitable as a primary treatment. It may still be used as a preventive measure before the disease appears.
In practical vineyard management, it's crucial to apply fungicides early, either during the initial stages of infection or before symptoms appear. A second application should be made every 10 days depending on weather conditions and disease progression. Typically, two to three applications are recommended. To prevent the development of resistance, it's advisable to rotate between different types of fungicides rather than relying on a single product repeatedly.
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