I have two favourite shrubs (in New Zealand), Viburnum carlessii and Viburnum burkwoodii. I planted them about 5 years ago and they seemed to thrive, putting on plenty of new growth and flowering freely. However, this season they appeared to struggle and now I am noticing quite a lot of dieback with dead branches going to the main stem. There doesn't appear to be any disease that I can see; however, some of the affected branches do have damage from our cicada, which injects its eggs into the stem and leaves quite a scar. Can you think of any other reason why these viburnums are dying back? Thanks.
Certified GKH Gardening Expert
They could be affected by a fungus, which could be attacking either the roots or the branches themselves. When the branches die, what does that look like? Do the leaves turn brown right off or does some other discoloration happen? Does the whole branch die at once or does it die in a certain pattern? Let us know and this will help us determine what is affecting the plants.