By The Old House Web


List of files and visuals associated with this text.

Scab is caused by the fungus Venturia inequalis. Infection takes place early in the season and dark olive green spots appear on the leaves. In late summer the infected leaves fall off when they turn yellow with black, spots. Infected fruits have black, slightly raised spots. Use resistant varieties.

Fire blight susceptible trees have blighted branch tips. The disease is caused by the bacterium Erwinia amylovora. Leaves on infected branch tips turn brown or black, droop, and hang on the branches. The leaves look scorched as by a fire. The trunk and main branches become infected when the bacteria are washed down the branches. Cankers form and are separated from adjacent healthy bark by a crack. The infected bark may be shredded. There is no satisfactory chemical control for fire blight. Use resistant cultivars when available.

Powdery mildew coats leaves with white powder and may be controlled with sprays of benomyl.

Rust causes brown to rusty-orange spots on the leaves. Red cedars are the alternate host. Badly spotted leaves fall prematurely.

Crab apples are subject to several canker diseases. Avoid unnecessary wounding, keep trees healthy, and prune out infected branches when seen.

Visuals associated with this text.

Visual title - Visual size Visual title - Visual size
Cedar Apple Rust - 40K Apple scab on overwintered leaf - 30K
Apple scab, mummified fruit with scab - 24K Apple scab, early summer defoliation - 81K
Apple scab lesions on fruit - 15K Cedar apple rust on juniper, spore horns - 40K
Cedar-apple rust on crabapple fruit - 42K Cedar apple rust on apple - 56K
Cedar apple rust gall on apple - 41K Fire blight on apple - 54K
Fire blight canker - 38K Fire blight canker on crabapple - 48K
Fireblight on crabapple - 50K Fireblight shepherds crook - 40K
Fireblight, tree with many strikes - 58K Fireblight, severe case - 53K
Fireblight canker - 37K Cedar apple rust on apple - 56K
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