taken from http://davesgarden.com/guides/articles/view/2615/
It?s heartbreaking. Your clematis vine is growing vigorously and bursting with plump buds, then seemingly overnight some or all of the plant collapses. Flowers, buds, leaves and stems first droop, then blacken and shrivel. It?s called ?clematis wilt? and while it may be difficult to eradicate, there are things you can do to control and prevent it. If you had a problem with clematis wilt this summer, autumn is the time to prevent its return.
What It Is The British call it “clematis wilt”, though some American gardening books refer to it as “clematis leaf and stem spot”. I prefer to call it “wilt” because it’s very descriptive of the problem! Fortunately the fungus does not attack the root system, so with care your clematis can return to health.
Clematis wilt is a fungal disease formerly called Ascochyta clematidina, now known as Phoma clematidina. It spreads by spores and is helped along by damp or humid weather. The fungus cuts off the plant’s circulatory system so no water can move through its veins, thus causing the wilt symptoms. The fungus can enter the plant through weakened or damaged stems, or can splash onto stems during watering or heavy rain. Plants that are tangled or that stay wet are even more prone to the fungus. Normally wilt appears in the early to mid-summer when the clematis is growing quickly. On an older plant, the woody portion near the ground is often the first place you will notice wilt. The dramatically beautiful larger-flowered varieties are, sadly, the most prone to the fungus. Species clematis and the smaller-flowered varieties, such as C. montana, C. macropetala, C. alpina and C. viticella are more resistant to wilt. Clematis wilt causes the foliage and stems to dry and whiter, possibly turning black. You may see reddish lesions along the stems, but the onset and spread of clematis wilt can be quick. You may not have any warning before an entire clematis vine turns brown. On the other hand, it’s not unusual for only a few stems to be affected.
How To Treat It At the first sign of wilt, cut the affected stems as close to the ground as possible. Be careful not to injure the healthy stems, especially those near the bottom. Remove any fallen leaves. Needless to say, you shouldn’t put these cuttings on your compost. Keep the roots watered, even after cutting out dead foliage. The fungus can overwinter in the dead foliage, so no matter which type of clematis you have, it is recommended that you remove all remaining growth in the fall. Dipping pruners into a weak bleach solution after each cut will prevent spread of the fungus to other plants. Following good sanitation procedures such as these will remove much of the infectious fungal spores and minimize any future problems. Denise Corkery, senior writer at Chicago Botanic Gardens, does not recommend chemical controls such as fungicide be used as treatment for clematis wilt. If you have this, now you know what it is called and what to do. With all of our moisture this summer, I can understand why we are getting it.
What Causes the Disease? Clematis wilt is spread by spores. Like most fugal diseases, is more prevalent in damp or humid weather. Plants that are tangled and remain wet well into the day are even more prone to attack. On older clematis plants, the woody portion near the ground is often the first area affected. The plant dies back because the fungus cuts off its circulatory system and no water can be carried through the plant. Left untreated, clematis wilt will spread throughout the plant and can kill a heavily infested plant. Clematis plants can recover from wilt, because it does not attack their root system. Till next time, this is Becky Litterer from Becky's Greenhouse, Dougherty, Iowa