Roses & Leaf Problems
Although found in gardens across the country, rose species require a great deal of care. They are susceptible to a number of diseases that affect their foliage. The symptoms vary depending upon the type of infection. Does this Spark an idea?
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Types
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The Diplocarpon rosae fungus causes rose black spot, a common foliage disease in rose plantings. The Sphaceloma rosarum fungus causes spot anthracnose in roses. The Phragmidium fungus causes rose rust, while the Podosphaera pannosa fungus causes powdery mildew infections.
Effects
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Rose black spot is characterized by black spots on leaves. Infected leaves turn yellow and fall from the plant, resulting in defoliation. The disease weakens roses and leaves them susceptible to winter damage, diseases and insect attacks. Roses with spot anthracnose have circular red or purple spots on the leaves. The centers of the spots sometimes turn gray, crack or drop out. Roses with rust infections develop a rust-colored growth on the lower surfaces of older leaves. Severe infections result in leaf loss. Powdery mildew infections create a powdery-white fungal growth on young foliage.
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Prevention/Solution
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Most fungi need wet leaves to germinate; using drip lines or soaker hoses, rather than overhead irrigation, and spacing plants so that they receive adequate air circulation prevents many fungal infections. Planting disease-resistant cultivars also helps limit outbreaks. Plants susceptible to leaf diseases are treated with timed applications of an appropriate fungicide throughout the growing season.
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