Medical importance: European hornets do not have barbed stingers (ovipositors) and as such, can sting repeatedly. Most stings resolve on their own and are approximately as painful as a honeybee sting, however individuals with a known allergy or exhibiting signs of allergic reaction should seek immediate medical attention. Tree climbers should be cautious when climbing trees that may have cavities or other suitable hornet nesting locations.
The European hornet (also known as giant hornet) was first reported in the US in 1840. It has since spread across much of eastern North America. It is native to parts of Europe and Asia and may be confused with our native cicada killer wasps, or a relatively new hornet reported in North America (not MA), Vespa mandarinia, which is also referred to as the giant hornet (or murder hornet or northern giant hornet; V. mandarinia is not currently found in Massachusetts). The European hornet (V. crabro germana) is large (1-1.3 inches in length), stout, hairy, and with reddish brown and yellow colors on the head. Their thorax is also reddish brown and black, and the abdomen behind it is black toward the top, yellow toward the back, and the yellow markings on the abdomen are interrupted by rows of black teardrop shaped markings. (V. mandarinia are larger than the European hornet and lack the teardrop shaped markings on the abdomen.) European hornets do not feed on the plants mentioned above, so they are technically not "hosts". However, they become damaged by the hornet's behavior that includes chewing the bark from twigs and branches and using this material to construct their nests. Plants damaged have been recorded up to almost 300 feet away from the colony or nest. Nests may be located in cavities of trees, holes in the ground*, or unfortunately sometimes wall voids in houses. (*However, they do tend to prefer protected aerial locations for their nests, such as higher up in trees.) The nests are called "paper" nests, similar to those of yellowjackets or bald-faced hornets, but different in the sense that they are often made in protected cavities (and not entirely exposed, like bald-faced hornet nests). They are often associated with forests or adjacent areas, or urban or suburban areas with sufficient tree cover. Nests are large in size and can contain 200-400 workers, but upwards of 1000 workers have been recorded in some nests. Fertilized queens overwinter in sheltered areas, and emerge to begin new nests each year. All other individuals, such as the workers, die and do not overwinter. Because new nests are built each season, having a V. crabro germana nest in one location one year does not guarantee that the insects will use that same location again the next. European hornets feed on other insects, including grasshoppers and wasps, to gather protein during much of the time they are active. In the fall, they begin to search for sugar and carbohydrates, typically in the form of fallen fruit or by stripping the bark off of plants to drink the sap.
Adults girdle stems and branches by chewing away bark on the aforementioned tree and shrub species, particularly in August and September. This damage may sometimes be confused for squirrel activity. In the fall, adults may feed on apples prior to harvest, or be attracted to dropped fruit found on the ground. This species has historically been a problem in eastern Massachusetts since 1993 (Robert Childs, Personal Communication).
Look for loss of bark, sometimes girdling of twigs and branches. May be mistaken for squirrel damage or damage from other vertebrates. This usually occurs late in the summer, particularly on lilac or the others mentioned above.
When bark loss is first noticed, a fine mesh netting can be placed over small shrubs/bushes to protect them from further damage. Turning off porch lights, which can attract European hornets, may also deter unwanted visitors. If a colony is located, wait until the first couple of hard frosts kill all of the workers. This can be a good tactic if the nest is not in close proximity to human activity where hornets and people may accidentally come into contact with one another. Additionally, their nests can be 30 ft. or more up in trees, so reaching them safely to manage them by other means may not be possible.
No significant natural enemies regulating European hornet populations in the US are noted.
None recorded. Chemical management options for European hornets in ornamental trees or shrubs are not listed as these insects are not feeding on the host plants above. Their nesting behavior involves chewing bark from twigs or branches, but this can occur up to 300 ft. away from their colony.
If European hornets have set up a nest inside a wall void of a building, contact a licensed professional specializing in structural/indoor pests. Do not block the external entrance of the colony in this scenario, as this may force the hornets to chew their way out by other means and allow them to enter the home. The management information here is specific to European hornet activity in landscaped settings (on trees and shrubs) and should not necessarily be used to make management decisions for scenarios involving buildings.
