Plant Diseases

Rust (on plants)

Rust (on plants)
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Most of the fungi known as "rust" attack ornamentals. Each is specific to a certain type of plant, although some cedar apple rust, for example, require two hosts. The spores are spread by wind and splashing water.

Target: Many plants, including roses, hollyhocks, and snapdragons; lawns.

Damage: Rust first appears as pustules on the undersides of leaves; the lesions are usually orange-yellow in color, but may also be brown or purple. Eventually, the upper leaf surfaces become mottled with yellow. Severely infected plants are stunted and may die.

Control: Resistant varieties, sanitation, good air circulation, and fungicides.

Notes: Clean up fallen debris; remove rust-infected leaves remaining on plants. Water overhead only in the morning on sunny days.