European Hornet
Contact: Eric Day, Manager, Insect Identification Laboratory
Publication 444-240, August 1996
European Hornet
Plants Attacked
Lilac, boxwood, Viburnum, fruit trees, birch,
willow, poplar, Ligustrum, Rhododendron, dogwood and other trees
and shrubs.
Description of Damage
The most conspicuous damage is due to the premature browning of
leaves on individual branches in August and September. European
hornets girdle smaller twigs and gnaw holes in the bark of larger
branches. The hornets chew off the bark in order to feed on the
sap that flows from the wound. Some of the bark fibers may be
used for nest construction. Often the portion of the twig above
the girdled area dies. Usually before the twig dies it tries to
regrow, causing an abnormal swelling above the wound. Although
injury becomes most noticeable in the fall, European hornets may
have been removing bark and collecting sap for a month or more.
Identification
The European hornet is a stout hornet approximately 1-inch long.
The color of the head and thorax is dark reddish brown with deep
yellow and brown black markings on the abdomen. The markings on
the abdomen are similar to the markings found on yellow jackets.
The European hornet resembles the cicada killer wasp but is more
robust and has more hair on the thorax and abdomen (but is not as
hairy as a bee). The European hornet, Vespa crabro germana, is
in the order Hymenoptera and family Vespidae.
Life History
Damage is most extensive in late summer and early fall when large
colonies have developed. The hornets build their nests in
protected areas such as hollow trees, hollow posts, partitions in
sheds, barns, porches, and attics. Mature nests generally
consist of 6- 8 horizontal combs, without the papery covering
associated with many other hornets' nests. Nests can be very
large, up to 2-3 feet in length, 20 inches in diameter and may
contain 800-1000 workers. Nests are annual and die out in
winter. These hornets have a large stinger and large poison sac
and the sting can be painful, but they do not appear to be
particularly aggressive or vicious.
Control
There is no known insecticidal control for use on host plants.
Attempt to locate the nest by following the hornet in its flight
to and from the nest. Wear protective clothing and destroy the
nest at night by placing an insecticidal dust into the nest
entrance, although even at night it is still possible to get
stung. European hornets fly at night and are attracted to lights
and windows.
Remarks
European hornets abandon their nest at the end of the year. A
single queen starts a new nest in the spring and this nest is at
first small and has few workers. The limited number of twigs and
branches that are damaged in the spring usually go unnoticed. By
the end of the summer when many workers are active the damage is
more prevalent and easy to spot, especially since girdled areas
are highly attractive to other foragers, such as flies and sap
beetles, which come to the wounds to collect sap, sometimes in
great numbers.
Further Reading
Drooz, Arnold T., Editor. 1985. Insect of Eastern Forests,
USDA, Forest Service. Miscellaneous Publication No. 1426.
Superintendent of Documents, U.S. Gov. Printing Office,
Washington, D.C. 20402.
Johnson, W.T. and H.H. Lyon. 1991. Insects that Feed on Trees
and Shrubs, 2nd Edition, Revised. Comstock Publishing
Associates, a division of Cornell University Press, 124 Roberts
Place, Ithaca, NY 14850. 241 color plates, 560 pages. ISBN
0-8014-2602-2.