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.