The Asian giant hornet (AGH), Vespa mandarinia, poses a substantial threat to the European honey bee, Apis mellifera, if it becomes established here. There have been confirmed sightings in Whatcom County and bordering Canadian locations, indicating that we should be on the lookout for this murderous predator.

Understanding this invasive insect’s characteristics and life cycle is critical to eliminating them before they spread and result in extensive damage to the local honey bee population, industry, environment and economy.

The AGH is the world’s largest hornet. It can be identified by size alone — at up to two-inches long, and like other social wasps, uses its stinger to protect itself. It is estimated that AGH can fly up to 25 miles per hour to distances of five miles or greater, however, the attacks on bee hives are more detrimental at distances of one-half to one mile from the nest.

The AGH is more common in Asia and Japan, where honey bees have cohabited and evolved, gaining defense mechanisms against the AGH. The European honey bee that we rely on for honey here has not acquired those natural protections and counter-attack strategies. The AGH’s preferred habitat is woodland areas of lower altitude, similar to our own climate.

The lifecycle starts with the AGH queen emerging in early spring, first searching for tree sap for nourishment before beginning her search for an underground safe haven to build her nest. She will work alone to construct the nest of wood shavings from nearby trees, lay eggs, collect food, and feed the brood until the first workers emerge to help her further erect the nest and forage for food in late spring.

The queen will taper off her duties to concentrate on laying eggs while the workers create bigger cells to house the virgin queens and drones. The colony increases in size, reaching maturity in summer.

In early fall, the colony has a growing demand for proteins and fat to feed the young, and at this stage workers seek out and attack honey bees and other prey. By the middle of fall, virgin queens emerge and mate with the drones waiting for them near the entrance of the nest. Towards the end of fall, the founding queen dies, the nest deteriorates, and the workers and males die off while the inseminated queens find a place to overwinter and the whole cycle starts again.

An AGH attack on a honey bee colony is a three-phase occurrence that begins with the “hunt.” On the search for proteins to feed the nest, the workers hunt unexclusively for honey bee hives. During this phase the workers kill individual bees, decapitate them, and ball up the remainder, carrying them back to feed the developing brood. In the process they leave behind pheromones to mark the bee hives. The pheromones are believed to help navigate nest-mates to the hives and will intensify aggressive behaviors in the hornets as part of the second “slaughter” phase.

The slaughter entails an army of AGH attacking relentlessly at a bee hive until all adult bees are killed. Within a few hours to a few days the entire colony of honey bees is decimated and the third phase of “occupation” begins. During occupation, the entry of the hive is guarded to protect the food and at this point the hornets become dangerously defensive and will attack other animals and humans. The remainder of the bee brood is mashed into a paste and carried back to the hornet nest as feed until all that is left of the hive is honey.

Where Asian cultures see these insects as a source of food, here they are considered a public health issue. They do not tend to be aggressive toward people, but they will attack when their nest or food source is threatened.

The AGH stinger is about a quarter of an inch long and can penetrate through a traditional beekeeper’s suit. The sting is described as excruciatingly painful and an individual hornet can sting repeatedly, injecting up to seven times the venom as the European honey bee. Causing an anaphylactic shock in people with allergies, a sufficient dose of venom can also be lethal to non-allergic victims.

If you are stung by an AGH, seek medical attention or call 911 if extreme swelling, anaphylactic shock or respiratory distress occurs. Also report the incident to the Washington State Department of Agriculture. For reporting AGH sightings and other related incidents, contact Washington State Department of Agriculture by calling 1-800-443-6684, emailing pestprogram@agr.wa.gov, or online at agr.wa.gov/hornets.

Specimen for viewing

The WSU Clallam Extension Office now has an Asian Giant Hornet specimen here in the office at the courtesy of Washington State Department of Agriculture. Come visit us at the courthouse to see it in person, located in the lobby of the Clallam County Courthouse (223 East 4th St., Port Angeles).

Michele Mangiantini is a WSU-certified Clallam County Master Gardener.

Beekeepers need to know

It is easiest to detect Asian giant hornet (AGH) workers from July to November while the colony is matured and most densely populated, however only mated queens can establish new populations. So, eradicating nests and killing queens would be more successful than tactics that kill mass quantities of workers.

Hobby beekeeper’s best option for preventing AGH establishment is to monitor by using baited sticky traps when queens emerge in late March and early April, and then again targeting queens and males during the November mating season. Targeting nests from July to October can be a concerted effort of recording/reporting initial sightings and using additional detection with baited traps to narrow down the nest location.

Contact the WSDA immediately when located and do not exterminate the nest yourself.

The WSDA is distributing sap-baited sticky boards aimed at attracting queens as they emerge from hibernation. There is a list of low-tech homemade AGH trap designs available through the USDA’s “New Pest Response Guidelines: Vespa mandarinia, Asian Giant Hornet.”

AGH kills are characterized by the death of all EHB adults and no brood left behind. If there are live bees left behind or no honey found in the hive, then most likely AGH was not the predator.

For more information about protecting honey bee hives from hornets, contact Tim Lawrence at 360-639-6061 or timothy.lawrence@wsu.edu.

AGH specimen for viewing

The WSU Clallam Extension Office now has an Asian Giant Hornet specimen here in the office at the courtesy of Washington State Department of Agriculture. Come visit us at the courthouse to see it in person, located in the lobby of the Clallam County Courthouse (223 East 4th St., Port Angeles). If you suspect that you have seen an Asian Giant Hornet, please report sightings to agr.wa.gov/hornets.

Home Garden Tour

The Master Gardener Foundation of Clallam County’s 27th Annual Home Garden Tour (“Petals & Pathways) is 10 a.m.-4 p.m. Saturday, June 25. Tickets are $15 in days prior to the tour, or $20 the day of the tour. Visit clallammgf.org/events-2020/petals-and-pathways-garden-tour.