The European hornet, Vespa crabro, is the only true hornet species established in North America, having been introduced from Europe around the mid-1800s. They prefer to build their large paper nests in hollow trees, wall voids, and attics. A mature colony can contain hundreds of workers by late summer, leading to increased activity and potential defensive behavior near the nest. These insects can also damage the bark of trees and shrubs by girdling them to collect wood pulp for their nests and sap for food. Proper identification is the first step in managing these insects effectively.
Confirming the Target: Identifying European Hornets
The European hornet is substantially larger than most wasps, with worker hornets typically measuring between one and one and a half inches in length. Their coloring is distinct, featuring a reddish-brown head and thorax, with an abdomen that is striped in a dull orange or yellowish-brown and brown pattern. This coloration distinguishes them from the much smaller, brighter yellow-and-black striped yellowjackets and the black-and-white patterned bald-faced hornets.
A key behavioral difference is that European hornets are active at night, unlike most other stinging insects. They are strongly attracted to light and may be seen flying against illuminated windows or outdoor light fixtures after dark. Their nests are almost always located in dark, sheltered cavities at least six feet off the ground, such as hollow trees, eaves, or structural voids. This preference for enclosed spaces contrasts with the free-hanging, exposed paper nests of the bald-faced hornet or the underground nests favored by many yellowjacket species.
Natural Enemies and Environmental Factors
The entire colony is annual; the workers and the old queen die off as cold weather arrives in late autumn. Only the newly fertilized queens hibernate, seeking shelter for the winter before emerging in the spring to start a new nest. This natural cycle causes the colony to collapse on its own every year.
Various predators feed on the hornets or their larvae. Larger mammals such as badgers, skunks, and bears may opportunistically raid nests for the protein-rich larvae inside. Certain birds, like the European Honey Buzzard, are specialized predators that target the larvae within the nest. Additionally, larger insects, including some species of robber flies, will prey on foraging hornets.
Safe Non-Chemical Removal Strategies
Non-chemical control methods focus on trapping foraging workers or physically excluding them from the nesting site. Trapping can be effective for reducing the number of foraging workers in a localized area, especially late in the season. Specialized traps use a combination of sweet bait, such as sugar water and vinegar, or protein bait, like fish or meat, to lure the hornets. The addition of vinegar or a banana peel to the sweet bait can help deter beneficial insects like honey bees from entering the trap.
Physical exclusion is another important strategy, particularly for nests located in structural voids. Once the hornet activity has naturally ceased in the winter, the old nest entrance should be permanently sealed with caulk or weatherstripping to prevent a new queen from establishing a colony in the same spot the following spring. Small infestations of foraging hornets can sometimes be managed with UV light traps that utilize a high-voltage electrical grid to kill the attracted insects. For a nest located in a wall void, non-toxic options like a dish soap and water solution can be sprayed directly into the entry point late at night to quickly kill the workers.
Targeted Insecticide and Professional Options
The most effective method for eradicating an active European hornet nest, especially one hidden in a wall void or attic, involves the targeted application of insecticide dust. Dust formulations containing active ingredients like deltamethrin or permethrin are preferred over liquid sprays for cavity nests. When applied with a bulb duster directly into the single nest entrance, the fine powder penetrates deep into the void and adheres to the hornets’ bodies.
The workers carry the contaminated dust inside, where it is transferred through grooming and feeding, contaminating the queen and the larvae. This results in the total collapse of the colony within a few days. Non-repellent liquid insecticides, such as those with the active ingredient thiamethoxam, can also be applied as a residual spray to surfaces where hornets frequently land. This delayed-action poison is then unknowingly transported back to the nest, functioning as a bait. Always read and follow the product label directions carefully and wear appropriate protective gear, treating the nest entrance at dusk when the hornets are least active.
Professional extermination should be considered when the nest is large, inaccessible, or if any household member has an allergy to stings. Nests located high up in trees, deep within wall cavities, or in other hard-to-reach areas often require specialized equipment, such as extension poles for dust application or thermal imaging to precisely locate the nest. Licensed professionals have access to highly effective commercial-grade products and the expertise to safely manage large colonies, minimizing the risk of aggressive defensive swarms. They can also provide guidance on sealing entry points post-treatment to prevent future infestations.