Scab and Rust Disease

Ornamental plants can add beautiful aesthetics to any landscape. However, their aesthetics can be compromised by a fungus that invades the plants called scab and rust disease.

When are my trees at risk and what should I look for?

Scab and rust diseases are caused by fungi that invade crabapple, apple, hawthorn common pear and other ornamental plants in the rose family. These organisms survive by invading and taking nutrition from green plants or other food sources. When a plant is invaded, tissue damage or death may result.

Fungi that can cause scab and rust diseases typically infects hosts in early spring. As the infected leaves grow, lesions or rust spots form on the surface of the leaf and it will begin to curl. If the lesions grow large enough to merge together, early defoliation can occur. Lesions can also form on fruits, but this will typically not affect the health of the plant.

Scab fungi overwinter on fallen leaves, fruit and infected twigs. Their spores release on cool, moist days in early spring when plants are beginning to bloom.

Many effective treatment and prevention options are available for scab and rust disease. Your local arborist will develop a prevention or treatment plan to address your specific property needs. Find your local arborist here or View the full PDF Here.

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