Guam is making its mark in the scientific community with a new study that reveals the devastating invasion of the greater banded hornet and its impacts to the local honey bee colonies. Local beekeepers and Guam’s state entomologist have warned for years that this hornet was a threat, and now, research shows just how serious the impact is.

A new study published this week in peer-reviewed journal Plos One reveals just how devastating the greater banded hornet is for Guam’s honey bee population.  Researchers tracked hornet activity over nearly a decade, confirming that the hornet has become firmly established on the island since its first discovery in 2016. 

In peak years, up to 12% of honey bee colonies are wiped out. The hornet hunts throughout the year in coordinated attacks, posing a serious threat to both local agriculture and the ecosystem.

Christopher Rosario, Biosecurity Division chief at the Guam Department of Agriculture and state entomologist, is the lead author. He detailed, "The key study of this paper was to really show the impact of greater banded hornets on Guam to the beekeeping industry. All over the world right now, hornets are spreading globally. It’s due to increased shipping trade between countries and these hornets will hitch a ride. All it takes is one queen to hitch a ride on an empty cargo, container or pretty much on a pallet."

Rosario says the study is especially important as Guam is a major transportation hub in the Pacific, connecting other Micronesian islands, the US mainland and Asia.  Guam has long experienced accidental introductions of invasive species with devastating results, like the brown tree snake and coconut rhinocerous beetle. 

"Because what generally happens when Guam gets invasives, it doesn’t take long until those invasives spread to Hawaii. Guam got coconut rhinoceros beetles in 2007 then proceeded to the Micronesisan islands, Rota and the Marshall Islands. And now of course Hawaii is affected by this beetle," said Rosario.

He says this study will help regulatory agencies and the scientific community to better prepare for these invasions with rapid response efforts.  "Before this study, greater banded hornets were not on the radar for invasive species and neither were they very well studied. They were mostly studied in their native range," he shared. "But now studying it in its invasive range, or outside of its native range, really gives the scientific community better information on how to manage the hornet if it ever gets into their country or their island jurisdiction."

The study’s findings are helping guide the fight against the hornet here at home.  The Guam Department of Agriculture is using new tracking methods, moving from tiny radio transmitters attached to hornets to Bluetooth transmitters, to locate nests and control the spread.

"Through the amount of data collected throughout the years, we feel that hornets are a big problem not just for the bees but also for the community, for basically as a public health hazard," he said. "These are stinging wasps so people with bee allergies can potentially be affected."

Public involvement has been critical, with the help of local residents and beekeepers reporting sightings.  "The beekeepers and the community really made the contribution to this paper in that reporting this pest helped us generate that [data], and helps us now tell the story of how hornets, how vespa tropica– the greater banded hornet, is invading Guam," he said.

The agency is urging the public to continue reporting hornet sightings, especially during the wet season, when activity spikes. 

In the meantime, research continues to pinpoint where these hornets specifically came from and its eating habits to find out whether its making an impact to other pollinators.