European Hornets on River Birch
My river birch is covered with European Hornets. Unfortunately, we cannot find their nest. It seems like they are eating the bark on the tree. Do you have any recommendations on how to treat this? Will they kill the tree? Any help is appreciated. Thank you.
Montgomery County Maryland
European hornets strip bark from river birch and other preferred trees (such as lilac) to make their nests and obtain nourishment from the sap. They make their nests in a cavity, such as a hollow tree or wall void that is about 6 feet or more above the ground. Their nests are difficult to locate. They rarely make suspended, football-shaped nests like bald-faced hornets.
Mature trees can typically withstand damage form European hornets, but there may be some branch dieback if the damage is extensive. These hornets are typically active only in late September to early October. If you want to remove them, the best method is to find and treat the nest with a wasp spray -- but be careful, they can be aggressive when defending a nest.
There is additional information about European hornets, and what you can do, on the following web pages.