Answer: The exact cause of clematis wilt is unknown, other than it is a fungal disease and it attacks the above ground parts of the plant but not the roots. So, there's really no way to stop the disease, even with preventative fungicidal sprays. Some clematis are more susceptible to the fungus than others, so if you have a whole garden full of clematis, you'll find some plants are not affected and others are. The best defense is to remove the affected plant parts as soon as you recognize the problem and to work carefully around the unaffected stems so you don't accidentally transfer the fungal spores to healthy plant parts. I wish there were something more to suggest, but reasearch shows that even regular fungicide applications provide only partial protection. I'm afraid that if your clematis is prone to wilt, you'll either have to routinely cut away the affected plant parts, or you'll need to replace your clematis with a healthy new plant.
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