Leaf curl on Korean Spice viburnum
I have three Korean Spice viburnum in their third season planted in a side yard. They have done well and this spring bloomed beautifully and showed wonderful growth. Shortly after blooming I began noticing leaf curl and sprayed them for aphids a few times over several weeks but didn't notice much result. During the hot weather a couple of weeks ago we were away for four days, returning home to find all of the leaves shed, just as though it were winter. They have begun growing back very slowly but the new leaves appear to be curled as well. See photos. Please advise!
Did you actually see aphids? We would expect them to be under leaves that are curled under. We hope that the sprays didn't burn the foliage. That is especially possible if the dilution rate used was for dormancy instead of active growth periods.
We do not see an identifiable insect or disease sign/symptom.
These leaves look somewhat distorted. Was any herbicide applied in that bed to the areas around the trees? Many herbicides will travel down through soil and kill tree roots. Check the label on any herbicides used.
Another possibility could be that the shrubs were planted too deeply. You should be able to see the flare of the shrub trunks, i.e. where the trunk widens as it goes into the soil. Planting too deeply will slowly kill trees and shrubs.
Another killer can be clay soil amended with too many organic amendments, creating a bathtub effect when it rains and drowning plants.
Here is information about some other cultural issues that will kill: http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG201%20Homeowner%20...
If you have voles in the bed, pull back some soil at the base of the plants and look for vole gnawing. You can find help with voles on our website. Use the search box.
If you find any new clues, feel free to reply to this.