Clematis is a family of flowering vines. Horticulturalists recognize more than 250 species and around 5,000 different cultivars as of 2010. Clematis plants have no serious pest problems, according to the Iowa State University Extension, but they are susceptible to several diseases.
Clematis wilt is the most serious problem that clematis enthusiasts face, according to the Washington State University Extension. Large-flowering species are particularly vulnerable. Clematis plantings also are susceptible to attacks from powdery mildew, rust and phytophthora root and stem rot.
The fungus Ascochyta clematidina that causes clematis wilt attacks the stems near the ground, causing rapid wilting and sudden die-back. The Erysiphe aquilegiae fungus causes white patches of powdery mildew on leaves. Rust fungus creates yellow, red or orange spore masses on the foliage, while Phytophthora fungus rots the stems and crowns, causing yellowing, stunted growth and die-back.
Clematis wilt kills only the above-ground parts of the plant and does not affect the roots, so the plant should come back in a few years. Prevent powdery mildew infections by spraying plants with a preventive fungicide before symptoms develop. Watering plants from below rather than above and applying a preventive fungicide will prevent rust infections. Fungicides can prevent phytophthora rot from occurring, but infected plants should be removed.