William F. Lyon
|Common Name||Scientific Name|
|European Hornet, Giant Hornet||Vespa crabro Linnaeus|
|German Hornet, Sand Hornet|
|Common Hornet, Brown Hornet|
The European hornet is the largest and only true hornet in Ohio. (The so-called baldfaced hornet is actually an aerial nesting yellowjacket.) Although beneficial since it feeds on live insects such as grasshoppers, caterpillars, flies and yellowjackets, the European hornet can fly at night and sting repeatedly in defense of its nest entrance. Sometimes it builds its nest too close to dwellings, hunts in human-use areas, becomes attracted to lights, strips bark from ornamental plants, eats tree fruits, and raids domestic honey bee hives.
European hornets are large, up to 1-1/4 inches long with the head and thorax (middle part) red-brown. The abdomen (rear part) is black with yellow markings. Sometimes they are confused with the baldfaced hornet, which has a black head, thorax and abdomen with white markings.
European hornets normally are a woodland species which builds its nests in hollow trees. Sometimes, nests are found in attics, hollow walls, bird houses, barns, and abandoned bee hives in unprotected places. Nests are covered with a thick, brown envelope (paper-like) composed of coarse, decayed wood fibers which are quite fragile. These nests may have more than one entrance. A mature colony will contain 1,500 to 3,000 cells in six to nine combs. The lower two to four combs contain queen cells. There usually are 200 to 400 workers during the peak population. The life cycle is similar to yellowjackets, with overwintering queens preparing nesting sites in the spring (usually in May). Queens make the nest and lay some eggs. At this time, as the first generation is growing, the queen cares for the larvae by hunting food and enlarging the nest. After larvae reach adulthood, they take over housekeeping, nest expansion, hunting, and caring for the new larvae. The queen lays eggs for the remainder of the year.
As the nest continues to grow in size and number of workers through the summer and early autumn, production of sexually active males and females begins to build up in July. Mating occurs and inseminated queens overwinter in protected places until next spring. After a heavy freeze in November, the nesting individuals die out.
During the summer, these hornets can fly at night and are often attracted to light. They sometimes fly into the beam of a flashlight (bumping into the cover glass) or appear at porch party lights, lantern lights at campsites, etc. Occasionally, some fly against windows, causing humans to believe they are trying to get inside to attack them. Workers girdle twigs and branches of numerous trees and shrubs including lilac, birch, ash, horse chestnut, dogwood, syringa, dahlia, rhododendron and boxwood. These plants are sometime killed. Much of girdling is done for sap collection, not fiber. Other homeowner complaints involve nesting too close to human-occupied structures; presence in picnic grounds and yards; eating ripe or near-ripe fruit such as apples, puncturing a hole and hollowing out the fruit; and raiding domestic honey bee hives. However, they are not as aggressive as yellowjacket wasps.
European hornets, when not in direct competition with humans for space and resources, are very beneficial by destroying harmful insect pests. Do not control these hornets unless necessary. They are primarily a forest species, having few contacts with humans and present a minimal stinging hazard.
The best control measure is to destroy the nest. Work in pairs, wear protective clothing (with bee veil if possible) to cover the body and do the treatment after dark when most hornets are inside the nest. Use a flashlight (red cellophane over lens) while the other person applies the pesticide. Nests may be difficult to locate and out of reach high into a tree or structure. There are literally hundreds of products labeled for wasp and hornet control. Use special wasp and hornet pressurized jet sprays containing synergized pyrethrins, resmethrin or carbamates and rapidly volatilizing organic solvents. Sprays are emitted in a long, narrow stream 15 to 20 feet. If the nest is hidden in a wall void, puff carbaryl (Sevin), pyrethrins (Drione), bendiocarb (Ficam) or deltamethrin (Delta Dust) powder or dust into the wall hole that is used as an entrance. Workers in time will carry the dust back to the queen, giving good kill. When hornet activity has ceased, remove and destroy the nest. If the nest is a considerable distance from the entrance, spraying the opening may have little immediate effect. Never plug the wall entrance after treatment as hornets may chew out another entrance into the house.
Poisoned meat baits, which may work well with some yellowjackets, are not effective against European hornets, which prey almost exclusively on live insects. For the occasional indoor hornet, simply collect with a vacuum cleaner or kill with a fly swatter.
Usually it is best to use the services of a licensed professional pest control operator who has the experience, equipment, training and pesticides to do the job correctly and efficiently.
This publication contains pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registration, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author, The Ohio State University and Ohio State University Extension assume no liability resulting from the use of these recommendations.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868