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What are the control methods for rose powdery mildew?

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Powdery mildew Powdery mildew mainly damages the leaves, tender shoots, flower buds, and flower stalks of roses. After tender leaves are infected, the leaves become wrinkled, curl into deformities, and sometimes turn purplish red. When old leaves are infected, nearly round, water-soaked chlorotic yellow spots appear on the leaf surface, and in severe cases the leaves wither and fall off. The affected parts of tender shoots and flower stalks swell slightly, and their tips bend toward the ground. After flower buds are infected, they cannot open or the flower form becomes deformed, and the surface of the affected parts is evenly covered with a white powdery layer. For roses grown in the open field, powdery mildew occurs more often in spring (May and June) and autumn (September and October), which are the peak periods of the disease.

Powdery mildew Powdery mildew mainly damages the leaves, tender shoots, flower buds, and flower stalks of roses. After tender leaves are infected, the leaves become wrinkled, curl into deformities, and sometimes turn purplish red. When old leaves are infected, nearly round, water-soaked chlorotic yellow spots appear on the leaf surface, and in severe cases the leaves wither and fall off. The affected parts of tender shoots and flower stalks swell slightly, and their tips bend toward the ground. After flower buds are infected, they cannot open or the flower form becomes deformed, and the surface of the affected parts is evenly covered with a white powdery layer. For roses grown in the open field, powdery mildew occurs more often in spring (May and June) and autumn (September and October), which are the peak periods of the disease. For roses grown in greenhouses, powdery mildew can occur year-round. When the room temperature is above 5°C, powdery mildew can occur and cause damage. When the temperature is high, humidity is high, it is hot and stuffy, and ventilation is poor, the disease is more severe.

Control measures 1. Nitrogen fertilizer should not be applied excessively; the amount of calcium and potassium fertilizer should be appropriately increased to make the plants grow vigorously and enhance disease resistance. 2. Before budding, spray 3 to 4 degrees Baumé lime sulfur mixture to eliminate overwintering pathogens. 3. In the early stage of the disease, spray 15% triadimefon 1000-fold solution or 50% carbendazim 800-fold solution.

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