There are many conditions that mimic clematis wilt - recall that the vines of the clematis are long and any trauma caused at the base (a cat deciding to take a nap where the stems emerge from the ground) can cause whole sections to die off.
Clematis wilt is caused by a fungus that is in the soil. It disrupts the stems' ability to take up water and so they wilt. I saw a statement on this website that there is no known cure or preventative. That is not so. If you believe your clematis has wilt, cut off the dead/leafspotted sections (sterilize the cutting implement with alcohol between cuts) to the ground and either burn or dispose of the sections by placing them in a plastic bag and putting them in the garbage.
Now, for the cure/preventative treatment: When planting a new clematis, prepare a soil drench of 2 teaspoons of Cleary's fungicide (available at Rosemania.com and other places) per gallon. Drench the soil around the plant. If it is not a newly planted clematis, after you have cut off the dead parts, perform the soil drench. This fungicide is systemic, and will protect your clematis. It will also, if applied after the wilt has been observed, prevent additional damage. Since the wilt does not kill the roots, whether treated or not, the plant will likely sprout new growth either this or next season. But the drench will prevent the cycle from repeating itself. Note that wilt is most problematic on the large flowered types of clematis, and is not as likely to occur on the viticella and alpina types. If you plan to continue enhancing your garden with clematis, the Cleary's is a good investment. Many clematis will outgrow this susceptibility. Mary Toomey, in her book,
Clematis - A Care Manual asserts that Perle d'Azure is susceptible to clematis wilt when it is immatur but is worth putting up with because of its beautiful flowers. I have a few of this variety and have not experienced wilt.
Proper protective precautions should be taken when using this or any other chemical in the garden.
Bob Lamm
