Clematis Blight : An Unwelcomed Garden Guest:
When summertime arrives with its warm rains, it also brings along some unwelcome guests in our gardens – plant diseases. One of the most dramatic of these is clematis blight, caused by a fungus now known as Calophoma clematidina. But we’ll stick with the simpler names: clematis blight or clematis wilt.
Understanding Blight and Wilt
Clematis blight shows its presence with dead leaf spots, especially during wet weather from late spring to summer. These spots often have a light brown center with a dark ring between the dead and healthy tissue. They might have edges defined by leaf veins, giving them a mosaic-like appearance. Now, let’s clarify the terms ‘blight’ and ‘wilt.’ Blight refers to a disease or injury in plants that causes lesions, withering, and parts like leaves and tubers dying. When a fungal pathogen affects the leaves before the stems, it’s called blight. But if the crown or stems are infected first, the leaves may wilt and then discolor. How the symptoms appear depends on where the infection starts and the environmental conditions. Unfortunately, wilt is often used to describe a specific group of plant diseases that spread through the vascular tissue (like oak wilt or Dutch elm disease).
Dealing with Clematis Blight
Now, let’s talk about how to handle this disease. Start with disease-free clematis plants planted where they get at least six hours of sunlight each day. Make sure they’re well-spaced, so the foliage can dry out, protecting them from foliar diseases. Pruning is crucial to remove diseased tissue. Dense, overgrown clematis can become a hotbed for this disease. Some varieties only bloom on old wood, so pruning out disease tissue might affect blooms. After pruning, consider applying fungicides from early spring through summer to keep your plants healthy. There are various fungicides available for clematis blight control, such as Daconil Weatherstik, Emblem, Orkestra, Pageant, Palladium, Postiva, and Trinity, so check the labels for recommendations.
Conclusion
In the end, clematis blight might not be fatal on its own, but it’s unsightly. Here’s the recipe for success: give your clematis enough sunlight, prune and space them to keep the leaves dry, use fungicides preventively, and prune out and dispose of any infected tissue.
References: van de Graff, P., O’Neill, T.M., Chartier-Hollis, J.M., and Joseph, M. E. 2001. Susceptibility of clematis varieties and species to stem infection by Phoma clematidina as an indicator for resistance to wilt. European J. of Plant Pathology 107:607-614.
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