Know the signs. True Clematis Wilt is a fungal disease (Phoma Clematidina) which can find its way into the plant - after stem damage by other causes. Clematis tend to lose their lower leaves later in the season and they usually go brown or black before falling off. It is a stem rot/leaf spot disease caused by the fungus, Ascochyta clematidina, which mainly affects large-flowered clematis hybrids.Species clematis, their cultivars, and small-flowered hybrids are much less susceptible. Clematis wilt is a common problem when growing clematis, especially with the fancier hybrids which have less resistance. Control. Irrigate plants in a manner that keeps water off the foliage. Wilt will also occur with very small infants soon after they are placed in their permanent spot in the garden. Clematis wilt: Plants with dark brown to black Ascochyta leaf spots develop a stem canker that … Clematis wilt is a condition that seems to affect the large flowered, spring blooming clematis more than other varieties. Clematis wilt is a disease of clematis caused by the fungus Calophoma clematidina (syn Phoma clematidina, Ascochyta clematidina). It is very quick to take hold, and a seemingly healthy plant one day, can turn into a drooping specimen the next - thereafter with the foliage dying off and a quick descent into death! Once the disease hits, there is no chemical treatment to stop it, but it rarely kills the plant. Ensure good air circulation around clematis stems. If those are the symptoms then the plant does indeed have clematis wilt. Clematis wilt (sometimes it can be called clematis leaf and stem spot) is a devastating fungal disease. Here is what to do to try to prevent it from happening to your clematis. Treatments are available to slow the growth of a crown gall and to minimize its damage, but these efforts will not kill this infection. Treatment only slows the progress of the disease and is not recommended. It is characterized by a complete collapse of either the entire plant, just one of the shoots, or just part of a shoot. Large-flowered hybrid cultivars are prone to clematis wilt whereas the species with smaller flowers such as clematis alpine or clematis viticella for instance seem to be much more resistant. Remove infected leaves as they are detected. Provided that the upper sections are green, this is not clematis wilt. Plants with clematis wilt disease will suddenly completely collapse overnight - the foliage turns black (not brown) and the veins take on a purple colour. Apply a fungicide to protect plants. It makes clematis vines shrivel and may cause death of the plant. In my opinion, this is the saddest-looking disease a plant could possibly develop. The most serious disease of clematis, a varied genus consisting of about 250 species, is commonly called clematis wilt. Rose Rosette.