Research published on invasive hornet's impact on beekeeping

Research published on invasive hornet's impact on beekeeping



The Guam Department of Agriculture has achieved a scientific milestone with the publication of its first peer-reviewed research on the invasive greater banded hornet, marking a shift from purely regulatory work to contributing data that could shape how Pacific islands respond to similar threats.

The study, published last Friday in the scientific journal PLOS ONE, analyzed nine years of hornet behavior and documented how the predator has devastated Guam's beekeeping industry since its arrival in 2016. In peak years, up to 12% of managed honeybee colonies have been lost annually to hornet attacks, according to a press release from the department.

"This new article that came out is a scientific journal that definitely helps our students from the university to be able to use as a reference article to invasive species," Christopher Rosario, biosecurity division chief at the Department of Agriculture and lead local author, told The Guam Daily Post in an interview Monday. "We're not only addressing invasive species at the regulatory level but also at the level of the scientific community."


The research documents how the invasive hornet (Vespa tropica) has become firmly established across Guam, with nests discovered in diverse locations from underground burrows to exposed tree branches in both urban and rural areas. The hornets attack bee colonies year-round, often sending multiple hornets to target a single hive in coordinated assaults that weaken colonies through repeated harassment.

Rosario told the Post that the publication serves a dual purpose beyond adding to scientific literature.

"Despite even me being in the government capacity, I still have the love for the science," he said. "Because science is what helps us collect the data, and it helps us better manage with the data in mind."

He added that the paper details not just the hornet's behavior but "how we're able to better manage it."

"These scientific papers are not just about science, but they also help us better address invasive species on the management side and on the regulatory side," Rosario said.

The study draws on an unusual wealth of data, combining beekeeper records, public reports through the Pest Hotline, nest collections, and video footage. That community involvement proved critical to tracking the hornet's spread and behavior patterns.


"The relationships we've built between (the Department of Agriculture), beekeepers, and the public have been crucial," Rosario said in the release. "Without public reporting, many nests may have remained undiscovered."

The research confirms what local beekeepers have experienced firsthand. Hornet activity peaks during the wet season, from July through December, when attacks intensify. Guam's honeybees have developed defensive behaviors, forming "bee carpets" at hive entrances, attempting to mob and overheat attacking hornets, and using acoustic signals to warn the colony. But these defenses often fail to prevent losses.

Preliminary analysis suggests the Guam hornets most closely resemble populations from continental Southeast Asia, though genetic testing is underway to confirm their origin.

"We are excited that one of our very own (Department of Agriculture) state entomologist led this work in cooperation with national and international scientists," Chelsa Muna, director of the Guam Department of Agriculture, said in the release. "By contributing to peer-reviewed science, we are elevating Guam's voice in understanding invasive species impacts in island ecosystems."

For Rosario, the collaborative nature of the research makes the achievement meaningful.

"With a lot of collaborators, international and national, this partner effort is what makes my job worth doing every day," he said.

The publication arrives as the department continues efforts to manage the hornet population through radio tracking technology and nest removal. While complete eradication appears unlikely for Guam, the island's experience and data could prove valuable if hornets spread to neighboring Pacific islands where rapid response might still prevent establishment.

The study's open-access format allows free use and adaptation of its findings, enabling other researchers and island managers to build on Guam's nine years of hard-won knowledge about Vespa tropica.

The department continues to encourage residents to report hornet sightings or suspected nests through the Pest Hotline at 475-7378, particularly during the wet season when hornet activity increases.