Although not usually necessary, applications of fungicides can be made when new growth emerges in the spring. Among the compounds registered for use in Connecticut are mancozeb, benomyl, and thiophanate-methyl. Consult the label for dosage rates and safety precautions. Rust, Puccinia violae . This is the most common disease of Viola in Connecticut.
Symptoms first appear as pale green spots on the upper leaf surface.
As the fungus grows within the leaf, diagnostic symptoms develop and can be seen on the under leaf surface. These appear as corky spots, blisters, or pustules which break open to reveal the rusty-brown spores for which this disease is named. Efforts to maximize plant vigor by fertilizing and watering are helpful. However, watering should be done early in the day to give the foliage a chance to dry before nighttime. This disease can be minimized by cleaning up plant refuse in the fall and by adequate spacing of the plants to promote good air circulation.