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.