Crown rot kills plants when weather conditions are moist and temperatures are above 60 degrees. Avoid infested soil. The disease is caused by Pellicularia rolfsii and no chemical control is listed.
Leaf spot diseases may disfigure the leaves but no chemical controls are listed.
Rust covers the undersides of leaves with orange or reddish brown pustules. The leaves will dry and the plants are stunted. Rusts are controlled with applications of sulfur.
Powdery mildew causes a white powdery growth on the leaves. Spray with benomyl or sulfur.
Root rot causes root decay and in wet weather a cobwebby growth develops on the lower stems. The lower leaves rot and upper parts of the plant wilt and die. Remove infected plants. No chemical control is listed for this disease caused by Pellicularia filamentosa.
Verticillium wilt may also attack Campanula. No chemical control is listed.