The Asian Giant Hornet (Vespa mandarinia) (AGH) is generating social media buzz bolstered by news feeds referring to it as the "murder hornet." However, nothing has changed since it was found late last season in the extreme northwest corner of Washington State and the southwest corner of British Columbia, Canada.
Thus far, AGH has not been confirmed anywhere else in North America including Ohio. But this does not mean we should be complacent. As other non-native insect pests have taught us, we must remain watchful.
Beekeepers should be particularly vigilant. AGH is a predator of other insects and extremely aggressive towards European honey bees (Apis mellifera). In fact, beekeepers are on the front lines in monitoring for AGH in Washington State.
Ohio Department of Agriculture (ODA) Responds
The ODA has created an AGH Reporting Tool so Ohioans can provide photographs and locations of suspicious insects. Although photographs can't serve as official confirmation, they are very helpful in making an initial identification before opening an investigation.
Here is the hotlink to the ODA's Asian Giant Hornet Online Reporting Portal:
https://agri.ohio.gov/wps/portal/gov/oda/divisions/plant-health/invasive-pests/agh
The Asian Giant Hornet
AGH is the world's largest hornet with a body length of 1.5 – 2" and a wingspan from 1.5 – 3". Two of its most notable features are its large orange or orangish-yellow head and distinct orangish-yellow and reddish-brown bands on its abdomen.
AGH produce annual underground nests often taking advantage of cavities created by burrowing rodents and other animals. Their seasonal development matches that of our own North American yellowjackets (Vespula spp.) and bald-faced hornets (Dolichovespula maculata) with the nests only being used for one season.
Despite the social media hype and dubious web postings, experts consistently note that AGH is not particularly hostile towards humans, pets, and large animals. As with our native yellowjackets and bald-faced hornets, AGH generally goes about its business unless its nest is threatened. Of course, swatting at an AGH may also elicit a painful introduction to its 1/4" stinger.
As noted above, AGH is an extremely aggressive predator of European honey bees. It will mass-attack honey bee hives and quickly dispatch the workers primarily by clipping off their heads. They then rip out the honey bee larvae and pupae, fly back to their underground nests and feed the mellifera meat morsels to their young.
This discriminating taste for honey bees is a two-edged sword. On one hand, AGH can be highly destructive by quickly devastating honey bee hives. On the other hand, their strong preference for honey bee meat means beehives are highly effective in revealing undetected AGH populations. For this reason, beekeepers are most likely to be the first people to observe AGH in an area where this non-native has established a new outpost.
Look-A-Likes
The two insects most commonly mistaken for AGH are European Hornets (V. crabro) and our native Cicada Killer Wasps (Sphecius speciosus). Cicada killers are the largest native wasp found in Ohio.
Cicada killer wasps will appear much later in the season with the arrival of their namesake food item, Annual Dog-Day Cicadas (Tibicen spp.; family Cicadidae), and disappear once annual cicada activity concludes for the season. Cicada killers create underground burrows. However, unlike AGH, the burrows are excavated and occupied by a single female wasp.
European hornets were first found in the U.S. in New York State around 1840. Since that time, the hornets have spread to most states east of the Mississippi and a few states to the west. These hornets are impressively large, measuring 1 - 1 1/4" in length. Their black and yellow markings on their abdomen make them look like yellowjackets on steroids; however, their head and thorax have distinct chestnut-colored markings. Yellowjackets have black and yellow markings on the head and thorax.
Technically, the non-native European hornet is the only "true hornet" found in Ohio. Taxonomically, our native bald-faced hornets are not hornets; they are grouped with yellowjackets which is why they are in the same genus as native Aerial Yellowjackets (D. arenaria).
Unlike our native yellowjackets and wasps, European hornets can cause noticeable girdling damage to twigs and branches of trees and shrubs by stripping bark to the white wood. It is speculated that the hornets are extracting sugar from the phloem tissue. Although the damage may be noticeable, it's seldom significant enough to cause concern.
European hornets construct paper nests that may look similar to the bald-faced hornet nests. However, they are most often found in hollow trees and sometimes in the walls of homes. They do not produce underground nests.
Normally, European hornets overwinter just like our native bald-faced hornets, paper wasps, and yellowjackets with only the queens that are produced this season surviving the winter. The new queens leave the nests to seek protected overwintering sites; old nests are not re-used. However, occasionally the entire European hornet nest will survive the winter if they are sufficiently protected. Indeed, although it is rare, nests in Ohio have been observed surviving through three winters.
European hornets are reputed to be highly aggressive and their large size does make them look pretty scary. However, during past encounters with this hornet, I was able to take close-up images and move branches with hornets on them without being stung or even charged. Still, landscapers should be cautious around these large stinging insects. Like wasps and yellowjackets, they are capable of stinging repeatedly.
The European hornets may also fly at night and are attracted to porch lights or lights shining through windows. They have been known to repeatedly charge windows at night inducing panic in homeowners.
Other Insects Found in Ohio
The following are a number of other native and non-native insects found in Ohio that may be mistaken for AGH.
More Giant Asian Hornet Information
The following websites provide updates on AGH in Washington State and British Columbia as well as details on the discoveries and official confirmations:
Washington State Department of Agriculture (WSDA) Pest Alert: Asian giant hornet
https://wastatedeptag.blogspot.com/2019/12/pest-alert-asian-giant-hornet.html
WSDA Asian Giant Hornet Reporting in Washington State
https://agr.wa.gov/departments/insects-pests-and-weeds/insects/hornets
Washington State University Extension, Additional Information on Asian Giant Hornet
https://extension.wsu.edu/wam/asian-giant-hornet-found-locally-what-we-know/
British Columbia Ministry of Agriculture, Three Asian giant hornets found in Nanaimo
https://news.gov.bc.ca/releases/2019AGRI0102-001759
British Columbia Ministry of Agriculture, Asian giant hornet nest eradicated in Nanaimo
https://news.gov.bc.ca/releases/2019AGRI0106-001818
British Columbia Ministry of Agriculture, Pest Alert: Asian Giant Hornet
