Anthracnose causes browning and blotching of the leaves. The dead areas have distinct black margins. The petals of infected flowers are abnormal or spotted. Severely infected plants may be killed. No control is listed.
Several leaf spots may be seen and are controlled by picking off infected leaves.
Powdery mildew cause a white powdery growth on the leaves. Benomyl should control the problem.
The disease called scab is also called spot anthracnose or pansy scab. Symptoms are circular to elongated lesions, one fourth inch in diameter, on all parts of the plant. The spots may be yellowish brown, rose colored, or whitish. Darker green zones may surround the spot. The diseased areas fall out giving a shothole appearance. The spots may change from irregular, to elongated raised scabs on the leaves and stems. When the stems or leaf stalks are girdled the part above the infection dies. Remove and burn old leaves. No chemical control is listed.
Stem rot attacks the stems at soil level. Diseased tissue becomes black and brittle and contains an abundance of black spore pustules. Infected leaves turn purplish black in spots or streaks. Infected tissues dry up, shrivel, and turn brown. No chemical control is listed.
Rust causes pale green spots on the undersides of leaves. Pustules containing yellowish spores develop on the upper leaf surface. Spots may develop on petioles and stems. Applications of sulfur control this disease.
Smut attacks all parts of the plants. Elongated or callus-like pustules, develop on, and deform, the leaf stalks. The pustules break open to discharge spore balls. Remove and destroy infected plants early in the season. No chemical control is listed.