University of Maryland Extension

Rust - Shrubs

  

azalea leaves infected with rust

Photo: Rust on azalea

Return to Common Problems of Shrubs

Deciduous azaleas are the primary group of broadleaved shrubs damaged by rust. Of the six rusts in North America, the hemlock-blueberry rust, Puccininastrum vaccinii, is the most common rust infecting deciduous azaleas in Maryland. It is only sporadically severe. Symptoms are easily recognized by the brightly colored yellow-brown spores present in disease pustules on the lower or upper surfaces of leaves. Another rust, occurring on blackberry, has bright orange spores on the underside of the leaves. Infected plants lose their leaves prematurely and show reduced growth. Other fungi may then attack weakened plants causing further injury. This rust also causes yellowing and leaf or needle drop on blueberry and hemlock.

Management:  Cultural practices such as removal of diseased leaves and proper plant spacing to maximize air circulation provide the best control. Selected use of fungicides should be considered only leaf loss is severe. Registered fungicides include sulfur and Bordeaux mixture. Problems with rust can be prevented or reduced by planting resistant varieties. Deciduous Azalea cultivars resistant to rust include "Red Velvet", "Buzzare", "Rapture", "Red Letter", and "Balzae".

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