Should You Worry About Bald-Faced Hornets?

As summer continues, bald-faced hornet nests get larger, and the number of hornets you see outside can increase substantially. The Plant and Insect Diagnostic Clinic has received several inquiries about bald-faced hornets since the start of August, and we’re here to tell you if you should worry, and what to do if you find a nest. 

Bald-faced hornet on yellow flower
Photo by Jon Yuschock, Bugwood.org

Bald-faced hornets are actually a type of aerial yellowjacket – a yellowjacket that makes their nest in the open environment instead of underground like many other yellowjacket species. They can be found in papery nests hanging from trees, under eaves of homes, or on other structures that provide protection from the elements. Nests can be remarkably large, sometimes the size of a basketball or larger. One opening near the bottom of the nest is the only way in or out for the hornets.

A single queen bald-faced hornet will begin constructing a nest in the spring. She will lay eggs and tend to these immature hornets that will soon develop into female workers. Once these female workers are developed, they will then do most of the work building the nest and caring for young as the queen continues to lay more eggs. By mid-to-late summer, nests peak in size and can include several hundred adult hornets.

Worker hornets will leave the nest to forage for food and collect materials to continue building the nest. They are most encountered around water sources, on wood structures that they chew wood fibers from to use for nest construction, or on sugary or protein-based food items (fallen fruits, animal droppings, occasionally around dumpsters, etc.).

Bald-faced hornet's nest in tree
Photo by David Stephens, Bugwood.org

Fortunately, bald-faced hornets are typically unaggressive unless they or their nest are disturbed. If a nest or hornet is found, do not try to get close or touch them. They may consider this a threat and sting. Most nests can be ignored if they are high up in a tree or on a house. However, if the nest is in a high-trafficked area, such as above an exterior doorway or in a low-hanging tree branch that you mow or tend a garden under, removal is acceptable. Aerosol insecticide sprays that can be applied from a safe distance (up to 20 feet) can be used to eliminate individuals in the nest, after which the nest can be removed. Professionals are recommended if you are known to have allergic reactions to stings or if you aren’t sure if all the wasps were killed with the insecticide.

It’s important to remember that bald-faced hornets are beneficial insects; they can help to manage garden pests such as grasshoppers. Most nests do not need to be removed, so long as they aren’t in high-trafficked areas or close to the ground.

Authors:

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on August 8, 2023. The information contained within may not be the most current and accurate depending on when it is accessed.