What could be causing my Viburnum to have yellow spots and curled leaves?
Question:
I’m seeing yellow spots on my Lil’ Ditty Witherod Viburnum and the leaves are starting to curl. I cannot see any insects though a nearby different variety Viburnum has visible aphid activity & curling leaves.
Answer:
I’m sorry to hear about the viburnum issues.
The visible aphid activity on nearby plants and the leaf curl suggests that this could be aphid damage, though it’s a little concerning that you can’t see any aphids on the plant pictured–I would recommend giving the plant another close inspection to see if you can spot any. If so, they can often be removed by spraying the viburnum vigorously with a jet of water. It’s also possible that you are looking at something like algal leaf spot (“Leaf spots start as small, pale green circular spots and eventually become light brown or reddish-brown with age.”) This might require waiting a bit to see if the spots progress into more recognizable symptoms; recommendations for treatment are in the link.
Because it isn’t a clear cut diagnosis, if neither of the above conditions seems to match up with what you’re seeing, I would recommend submitting either your photos or a physical sample to the UMaine Plant Disease Diagnostic Lab for confirmation. Their testing and diagnoses will always be more definitive, though there is a small cost for the lab’s services.