Leaf spot and stem rot disease girdles and kills infected stems. Individual shoots may suddenly wilt and die. The causal organism is Ascochyta clematidina and no chemical control is listed.
A number of leaf spots are seen on clematis. Pick off infected leaves when seen. No chemical control is listed.
Powdery mildew causes a white powdery growth on the leaves. Spray with benomyl or sulfur.
Crown gall attacks the vines near soil level. The galls are roundish with an irregular rough surface. Destroy infected plants and avoid infested soil. No chemical control is listed.