Problem Identifier Unit Screen//v.w/ RR Template

Problem Identifier Unit Screen//v.w/ RR Template Rust

Problem
Yellow to brown spots, up to ¼ inch in diameter, appear on the upper surfaces of the leaves, starting in the spring or late fall. The lower leaves are affected first. On the undersides of the leaves are spots or blotches containing a red, orange, or black powdery material that can be scraped off. Infected leaves may become twisted and dry, and drop off the plant, or they may remain attached. Twigs may also be infected. Severely infected plants lack vigor.

Analysis
Rose rust is caused by any of several species of fungi (Phragmidium species) that infest only rose plants. Rose varieties differ in their susceptibility to rust. The orange fungal spores are spread by wind to rose leaves. With moisture (rain, dew, or fog) and moderate temperatures (55° to 75°F), the spores enter the tissue on the undersides of the leaves. Spots develop directly above, on the upper surfaces. In the fall, black spores develop in the spots. These spores can survive the winter on dead leaves. In spring, the fungus produces the spores that cause new infections. Rust may also infect and damage young twigs.

Solution
At the first sign of rust, pick off and destroy the infected leaves and spray with a fungicide containing triforine. Repeat at intervals of 7 to 14 days for as long as conditions remain favorable for infection. Rake up and destroy infected leaves in the fall. Prune off and destroy infected twigs. Apply a lime-sulfur spray during the dormant season. Plant resistant varieties (for a list, see Roses Resistant to Black Spot, Powdery Mildew or Rust).

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