When the killer wasp First appearing in the United States in December 2019, the invasive insect brought with it a series of provocative headlines. Thousands of bee corpses were found in bee fields in Washington State. In one year, about 50 people died in Japan and another 42 in China due to the bites of the invasive species. Entomologists traced its presence to British Columbia, Canada, confirming the wasp’s spread. Five years later there is news of this battle. The authorities of the Department of Agriculture have declared the eradication of this species, the Vespa mandariniain Washington State and across the country.
The announcement came Wednesday and follows three years without confirmed sightings of this type of wasp, with the black thorax and orange head. Their jaws are so powerful that they have the ability to split bees in half, attacks that are especially common at the end of summer and beginning of autumn in the northern hemisphere. “My team has dedicated years of very hard work to guarding the state and the nation against this invasive threat to our pollinators and agriculture,” said Derek Sandison, the director of the Department of Agriculture in Washington, the region that became the main battlefield in the last five years.
Sandison assures that if this species had not been eliminated, the country would have faced a serious threat to its population of bees and other native insects. When they attack, killer wasps secrete a pheromone with which they mark the honeycomb, making it their target. Typically when the worker bees feed the queen and the drones leave the site to mate. The mark indicates to the rest of the wasps the site of the attack. Fifty of these insects then descend on the colony to completely eliminate it in less than 90 minutes. Eradication puts the bees out of harm’s way until the next pest appears.
The authorities had also warned since 2020 of the lower risk for humans. In the United States, about 72 people die annually from bee or wasp stings, according to official figures. None of these deaths have been linked to a murder wasp in this period. Detecting this type of wasps was difficult for the untrained eye, as they could be confused with other insects. A strong campaign was necessary.
The eradication was possible thanks to the work of both federal and state scientists and specialists. Those responsible for Agriculture in Washington have highlighted, however, the work of the public in reporting nest sightings. Nearly half of the detections came from reports generated by people and citizen scientists, who monitored traps and native wasp populations.
This allowed the removal of four wasp nests between October 2020 and August and September 2021. All of these were embedded in cavities of common alder trees. These operations were carried out with special tools such as telemetric tags that made it possible to follow the movements of the insects and thus be able to locate their nests. These were removed by teams of scientists wearing suits specially designed to protect against potential attacks by this species.
The capture of these nests also helped to better understand this type of giant wasp, formerly known as the Asian wasp. The Department of Agriculture says that although these insects appeared in Canada and Washington State just a few months apart in 2019, genetic analyzes actually suggest that they are specimens that came from different countries.
Tracking continued in Washington throughout 2024, especially in Whatcom County, a region in the extreme corner of the northwest United States that borders Canada. There were no sightings of wasps in the multiple traps placed in the area, which has allowed local authorities to claim victory.
Surveillance continues
Last October, monitoring services received a call from south of Port Orchard, west of the city of Seattle, who claimed to have seen a specimen of the Vespa mandarinia. However, entomologists were unable to see or obtain the specimen. “Without it, authorities could not confirm the presence of the wasp in a new county.” [Kitsap] and thus add it to our records,” says Sven Spichiger, pest control manager for the Washington State Department of Agriculture. “In the image you can see a species of wasp, but we don’t know how it got to that county,” he adds.
After the call, local authorities set several traps in the area as a precaution. They have also asked the population of the area to collaborate in communicating in case they see an insect with the description of the murder wasp again. At this time, there is no evidence of a presence in Kitsap County. Authorities will continue to monitor the area throughout 2025 as a preventative measure. Three years without records suggests that the war is over. For now.
