How can you treat an Alleghany Viburnam that dropped leaves?
Question:
Alleghany Viburnam dropped leaves which turned brown and curled up. I don’t know if this is an insect or fungus problem or something else. How can I fix?
Answer:
I’m not sure from the wording of your question if the leaves browned and curled before or after dropping. The latter would probably just be typical fall drop in a deciduous plant, so I will assume it’s the former. It’s tough to diagnose what might be going on from the description. Generally, viburnums are pretty hardy shrubs, but there are a few potential causes of foliage problems, as you can read about in this great fact sheet from the Clemson Univ Extension. If you noticed any holes or chewed edges, it’s possible that you have Viburnum leaf beetles, though Allegheny viburnum (Viburnum rhytidophylloides) is moderately resistant to the pest.
If your shrubs struggle to leaf out this spring, I would advise digging down and inspecting the roots for rot (in which case you’ll probably need to remove them). If they do leaf out normally, you are probably looking at a fungal pathogen and we would like to see photos of the plant, or have you submit a sample to the UMaine Plant Disease Diagnostic Lab, for diagnosis. Maine had a particularly wet year in 2023 and fungal infections were rampant across the state, affecting a lot of different species–removal of the leaves once they’ve dropped would be a key component to controlling the issue, as many spores overwinter in the detritus. Everyone is hoping for a drier year to mitigate such problems.
If the foliage issue recurs this year, I recommend sending along close-up photos of the affected leaves, as well as shots of the overall shrub, so we can get a better idea of what you’re dealing with. Then we can help you determine the best course of action.
Happy gardening.