Pestworld Magazine Focusing on the Business of Pest Management
The Asian Giant Hornet (AGH), Vespa mandarinia, gained notoriety in 2020 as the “murder hornet,” a name referred to by multiple media outlets throughout the United States. The AGH was discovered in 2019 in British Columbia, Canada, and then again discovered in not only Canada but also in Northwest Washington state in 2020. The AGH is an invasive wasp that is native to Asia and is the largest species of hornet in the world, reaching two inches in length and up to a three-inch wingspan.
The AGH is a social wasp species that construct underground nests in pre-existing holes or burrows. Mated queens begin the lifecycle in the spring and will seek and find a suitable spot to begin establishing a colony. The colony will grow over the summer and begin producing reproductives in the fall to mate, and then mated females will overwinter to begin the process again the following year.
AGHs will attack and destroy honeybee hives. They enter a “slaughter phase” and will kill honeybees by cutting their heads off and can entirely decimate a honeybee colony in a few hours. They will consume the brood of the honeybees and will also feed their own young the immature honeybees. These hornets will sting people if disturbed with a potent venom and have a tendency to sting repeatedly. While they do have a powerful sting, they are mostly a concern for anyone who is allergic to bee or wasp stings.
While there were a few single sightings of AGH workers in Washington and Canada, in late May 2020, the first queen was detected in Custer, WA. The Washington State Department of Agriculture (WSDA) began placing traps around the state in June 2020 in areas where sightings had been confirmed of AGH. Not long after, another AGH queen was detected further south in Bellingham, WA. Several other captures occurred in June and July, including a worker and a male AGH.
In September, a resident notified WSDA about a possible sighting and the first live AGH was captured. In October, another live AGH was captured and a tracking device was put onto the live AGH to see if the hornet could be tracked to the location of the colony. WSDA was able to follow the path of the hornet for about an hour before the signal dropped.
On October 21, 2020, using the tracking device again on a hornet, the very first nest of AGH was found in the U.S. This led to an extensive effort by WSDA, wearing extreme protective suits, to eradicate the nest. They first vacuumed out as many hornets as possible, followed by application of CO2 in the cavity to kill the remaining hornets inside. Four days later, the tree was cut down and the portion containing the hornet cavity placed into a freezer to kill any remaining hornets.
Beginning in July 2021, WSDA will start placing traps in areas with confirmed sightings up to a 5-mile radius of the center of confirmation. As of early May 2021, there have not been any confirmed sightings of AGH by WSDA or from British Columbia, Canada, but we will have more details once trapping begins and the wasps become active again in later summer. For updated information, visit https://agr.wa.gov/departments/insects-pests-and-weeds/insects/hornets.
BY BRITTANY CAMPBELL, PHD, BCE, DIRECTOR OF TECHNICAL SERVICES, NPMA
