European Hornets girdling a young river birch
Hi, I just planted these clump river birches this year and noticed a number of European hornets on them this weekend. They are girdling the tree and I am concerned they will kill my tress before the trees are established. This photo was taken on Sunday and they have kept at it all week! I don't see any signs of a nest nearby. What can I do to get rid of them/get them to leave my trees alone? Thanks, Allison
Here is our page on European hornets: http://extension.umd.edu/hgic/european-hornets
Unless you know where the nest is, control is difficult.
How large is this new tree? Is this damage mostly near the top?
It is unlikely that it will kill the tree, but if the damage goes all the way around the branch it will die back to that point but sprout again (2 branches in a fork) from beneath. This might be totally acceptable if it is higher in the canopy, which we can't tell from your photo.
If the tree is small enough, you could try draping the whole thing in tulle or floating row cover fabric to encourage them to go elsewhere.
A last option is to spray the bark (not the leaves) with a synthetic pyrethroid pesticide labeled for trees and shrubs.