Answer: Sounds like a disease called clematis wilt. Clematis wilt is a condition that seems to affect the large flowered, spring blooming clematis more than other varieties. It is characterized by a complete collapse of either the entire plant, just one of the shoots, or just part of a shoot.
The good news is that wilt is rarely fatal to the plant. It might take up to a year, but the plant will usually sprout a vigorous shoot from under the ground to live another day.
Until the real cause of clematis wilt is known, most growers use a systemic fungicide called Benomyl (Benlate) both as a prophylactic and as a cure for the problem. Most mix up a solution from the powder and soak the roots with a generous watering. This can be done at the time of planting, every spring, and right after the wilt occurs. The wilted portion of the plant should be pruned away and thrown in the trash.
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