I have several Mohawk viburnums that are sick; one has already lost a great deal of its growth. What can I do to protect the remaining shrubs? I did not find any insect or fungus grwoth, the leaves just die and then the branches.
The Gardener’s Answer
Hello, Patricia: Mohawk viburnums are known for their brilliant red flower buds that open to white blossoms with a spicy fragrance. This viburnum is a hybrid between burkwoodii and carlesii, which makes this cultivar resistant to bacterial leaf spot as well as powdery mildew. How old are your shrubs and have you used any sulfur sprays on your plants? Making sure they are planted in ideal growing conditions is important for the health of your shrubs. In general, viburnums are quite adaptable to most soil conditions, but prefer soil that is acidic and well-drained but moist. These deciduous shrubs should be planted in full to part sun, meaning they should receive at least four hours of sunlight each day. Good air circulation is important in preventing disease, as well as avoiding overhead watering. All plants are susceptible to insect/disease problems when they are not planted in an ideal location. From what you have described, it sounds like your shrubs may have shoot blight, which is a fungus (Botrytis cinerea) that first affects the foliage and eventually can cause twig dieback. It is difficult to say for sure not being able to see your viburnums, so for a positive diagnosis you should take a sample to your Cooperative Extension service or to a local garden center with a knowledgeable staff. For now, remove and destroy all infected parts and keep the area around your shrubs free of plant debris.