Apple powdery mildew is a common disease in Chinese apple-growing regions, causing significant losses to growers. Here are the preventive measures:
Symptoms of Apple Powdery Mildew
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Branches: White powdery layer covering the surface, shortened internodes, elongated leaves, and browning and wilting of affected shoots.
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Buds: Shrivelled and thin buds, failure of severely affected buds to sprout in spring, delayed sprouting in mildly affected ones, and appearance of powdery layer on new shoots.
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Leaves: White powdery growth on both sides, purple coloration of new leaves, wrinkling and deformation, later spreading of white powdery layer, uneven coloration on upper side, and wrinkling or unevenness on lower side.
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Flowers: White powdery spots on calyx or pedicel, deformity of sepals and pedicels, elongated petals, and pale green color.
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Fruits: Mostly affected in early stages, with white powdery spots near the calyx, hardening of affected areas, and elongation of fruits.
Preventive Measures
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Apply Sufficient Autumn Base Fertilizer: Enhances tree vigor, boosts disease resistance, and prevents overgrowth.
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Thorough Spring and Summer Inspections: Prune affected shoots promptly and dispose of them properly. Keep orchards clean and spray preventive fungicides like sulfur and propiconazole.
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Optimize Planting Density: Improve ventilation and light conditions to reduce disease incidence.
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Control Nitrogen Fertilization: Ensure balanced nitrogen, phosphorus, and potassium levels, with additional phosphorus and potassium fertilization.
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Focus on Spring Protection: Apply fungicides like triadimefon or methyl thiophanate at the beginning of the disease. Spray three times before flowering, 70% petal fall, and 10 days later, adjusting spraying based on disease progression.
These are the preventive measures for apple powdery mildew. Besides affecting apples, powdery mildew also harms pears, quinces, and hawthorns, emphasizing the need for effective preventive measures.
