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.
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.