IDENTIFICATION — You’ll spot powdery rust, orange or brown spots, like these on a snapdragon, on either side of the leaf. It’s most common in summer and fall, but can appear at any time.?
DAMAGE — Rust spores are carried by wind and water to infect plants during humid conditions. Affected plants include geraniums, asters, mums, snapdragons and peonies and also surrounding plants. Not only is it unsightly, rust weakens the plant, reducing flower and fruit production.
CONTROL — Remove and destroy infected leaves. Try to keep the foliage dry when you water and improve air circulation around the plant by removing dense vegetation nearby. Also, read descriptions to find resistant cultivars for your garden. If you still want to grow a susceptible plant, check with your local garden center for a fungicide you can spray in early summer as a preventative measure.