Grape downy mildew is a serious fungal disease that primarily affects the leaves of grapevines, often leading to significant leaf loss. In addition to damaging the foliage, it can also infect young shoots, flower clusters, and developing fruit, causing stunted growth and deformed tissues. When the infection becomes severe, the affected parts may die off, resulting in premature dropping of the fruit clusters. This not only reduces the current year's yield but also weakens the vines, making them more susceptible to winter damage, which can negatively impact the following season's production.
To find effective treatments for this disease, researchers from the Division of Plant Protection at Yantai Academy of Agricultural Sciences in Shandong Province, including Shu Ding, conducted field trials using several fungicides. Among them were Baitai (60% pyraclostrobin water dispersible granules) and four other products: Product-run (70% dextrose dry suspension), Kairun (25% pyrazophos emulsifiable concentrate), Kelu (72% copper oxychloride wettable powder), and 80% phosphinothric acid wettable powder. The trial was carried out in vineyards heavily infected with downy mildew, with each treatment applied every 10 days over three consecutive applications. A control group was treated with plain water.
The results showed that in the untreated plots, the disease continued to spread rapidly. Leaves became covered with a white mold layer on the underside, and many turned brown and fell off. In contrast, the treated areas showed much better control. Seven days after the second application, Kairun demonstrated the highest efficacy at 93.83%, significantly outperforming the other treatments. By the time of the third treatment, all fungicides achieved an effectiveness rate above 81.26%. Notably, Baitai showed excellent performance, with a control rate of 98.15% and 97.38% in the two assessments, far surpassing Kelu and phosphinothric acid.
The study confirmed that Baitai and Kairun are highly effective against grape downy mildew. Although Kelu and phosphinothric acid had lower efficacy, they still reached over 88%, making them viable options for disease management. However, Jinrun’s control effect was only 81.26%, which is insufficient as a primary treatment but could be used as a preventive measure before the disease appears.
In practical vineyard management, it's crucial to apply fungicides early, either before or during the initial stages of the disease. Depending on weather conditions and disease progression, repeated applications every 10 days are recommended. Typically, two to three treatments are needed for optimal control. To prevent the development of resistance, it's advisable to rotate between different types of fungicides rather than relying on a single product. This approach ensures long-term effectiveness and sustainable disease management.
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