Having recently spread from Asia to eastern Europe, Tropilaelaps mercedesae mites could threaten honey bees worldwide, researchers say, but decades of hard-won lessons from managing Varroa destructor may help scientists and beekeepers detect, track, and control the emerging pests before they spread farther and losses escalate. Shown here are two Tropilaelaps mites on a bee larva. (Photo courtesy of Maggie Gill, Ph.D., PHIRA-Science)

By Carolyn Bernhardt

“About half a century after Varroa destructor spread across Europe, history now appears to be repeating itself,” says Aleksander Uzunov, Ph.D., a professor at Ss. Cyril and Methodius University in Skopje, North Macedonia, and the Macedonian Academy of Sciences and Arts. “But this time, with Tropilaelaps mercedesae, the situation feels different.”

Tropilaelaps mites (which researchers sometimes call “Tropi mites,” for short) have recently spread from Asia to Eastern Europe, posing a serious threat to honey bee (Apis mellifera) colonies. How can decades of research on Varroa mites provide experts and beekeepers with the tools they need to address this new challenge?

“There is a much better understanding of honey bee diseases now than when Varroa mites first appeared,” says Jean-Pierre Y. Scheerlinck, Ph.D., an honorary professor in animal biotechnology at the University of Melbourne’s Veterinary School. Initially, Varroa did not infect Apis mellifera with deformed wing virus (DWV), but by the mid-1990s, Varroa had acquired and spread the virus globally. Tropilaelaps mites already carry DWV and black queen cell virus, giving experts no time to study the pest before it becomes lethal. Although the internet and genetic-testing techniques like PCR (polymerase chain reaction) didn’t exist when Varroa emerged, researchers and beekeepers alike now have better tools and are more vigilant in monitoring threats to honey bee health.

“The knowledge on Varroa biology and epidemiology can serve as a good example and starting point,” says Uzunov, “though the challenge is to not assume everything that worked for Varroa automatically works for Tropi.”

Experts in Europe are now laser-focused on developing surveillance mechanisms to prevent the spread of Tropilaelaps mites, probing their life cycle and habits and pinpointing where and when management tactics can be most effective. They’re churning out high-quality research, applying hard-won insights from studying the Varroa mite, and parsing key similarities and differences between the species.

Acting Before Arrival

Aleksander Uzunov, Ph.D

“One of the most important lessons [Varroa mites taught us] is delayed detection dramatically worsens outcomes,” Uzunov says. “With Tropilaelaps mites, this mistake must not be repeated.”

In a few places, Scheerlinck says, hive and bee movement restrictions remain in place to prevent Varroa‘s spread, but since Varroa has already spread to most parts of the world, this has become largely ineffective. “In the case of Tropi,” Scheerlinck says, “these types of movement restrictions would still be valuable if implemented consistently, because most of the world is still free of Tropi.”

“The most important aspect today is preventing arrival at all,” says Cecilia Costa, Ph.D., a senior researcher at the Italian Council for Agricultural Research and Economics. She, Uzunov, and their colleagues recently identified a potential pathway for Tropilaelaps to spread from Asia to Europe: the accidental introduction of an Apis florea colony in Malta. She says this event highlights how easily invasive parasites and pathogens can spread to new regions. In response, she and collaborators issued a policy brief aimed at local, national, and European authorities to raise awareness of the risks this poses to beekeeping.

Cecilia Costa, Ph.D.

In the meantime, beekeepers anxiously await research-backed management tactics they can deploy, should they find Tropilaelaps mites infiltrating their hives.

A New Relationship With Miticides

Worldwide, beekeepers largely rely on chemicals to control Varroa. “One tough lesson has been that acaricides may not be efficient forever,” says Costa, noting Varroa mites have repeatedly developed resistance to treatments—and no new active ingredients have been introduced for decades. This has led to more frequent, yet often unsuccessful, treatments—as seen in the severe U.S. colony losses during winter 2025. Costa warns a similar situation may arise with Tropilaelaps mites, given their biological similarities to Varroa.

To complicate things further, the timing of existing treatments may be trickier with the new pest. “Most treatments against both mites are effective primarily when they are on adult bees outside of the brood cells, where their reproduction occurs,” says Marin Kovačić, Ph.D., an assistant professor at the Faculty of Agrobiotechnical Sciences Osijek, Croatia, who works closely with Uzunov and Costa. Varroa, he says, spends several days on adult bees between reproductive cycles, whereas Tropilaelaps remains on adult bees for around a day. This shorter window limits treatment opportunities, so effective strategies may need to rely more on tactics or compounds that can penetrate capped brood cells and target reproducing mites.

Marin Kovačić, Ph.D.

Kovačić says induced brood interruption, a technique developed to enhance Varroa acaricidal treatments, could help ward off Tropilaelaps. Temporarily halting brood production enhances the effectiveness of miticide treatments by exposing more mites tucked away in the capped cells. Once Tropilaelaps mites are exposed, beekeepers can use fewer chemicals on their hives while achieving better results.

“In the case of Tropi, these techniques may even replace the need for chemical treatment, given these mites’ inability to survive outside the brood for more than a few days,” Kovačić says, adding that some research has already shown a comparable effectiveness of brood interruption and chemical treatments on Tropilaelaps. “The caveat is Tropi population growth in the colony is faster than Varroa‘s, and timing of the control actions will need to be carefully calibrated.”

“More widespread adoption of brood interruption techniques to combat Tropi would also have a knockout effect on Varroa,” Costa says.

Breeding for Resistance

Costa says breeding bees for mite-resistant traits—a strategy already used in Varroa management—could also help with Tropilaelaps. Varroa has reduced feral honey bee colonies, cutting down unmanaged pest reservoirs and revealing resistant strains researchers are now using as a starting point for selective breeding. Genetic resistance is more durable and sustainable than miticide use, since the pest can’t overcome it as easily, and the approach doesn’t leave chemical residues behind in the ecosystem.

But Scheerlinck says tactics like brood breaking and selective breeding can be labor-intensive and difficult to scale for large beekeeping operations. Plus, he says, “A colony infested with both Tropi and Varroa may need to be treated with different, lethal miticides. The combined effect of both miticides may be much more lethal than the single use of both miticides at different times.”

“The latest results from our ongoing research indicate that using formic acid to control both Tropi and Varroa mite species is promising,” says Kocačić. Still, he calls for further research to understand the challenges of applying treatments at the right moment to effectively suppress mites without compromising hive products. This balance, he says, will be crucial for developing practical, safe strategies beekeepers can rely on.

Knowledge Into Action

Ultimately, Uzunov lays out the priorities for researchers as they face what lies ahead with Tropilaelaps: “Emphasis should be placed on early warning systems, routine monitoring, and the development of simple methods that allow beekeepers to identify infestations before populations explode,” he says, advocating for updating maps of T. mercedesae distribution, invasion pathways, and risk zones to help both researchers and beekeepers determine where to prioritize surveillance and preparedness.

“Compared to when Varroa arrived, we already have much more information on Tropi biology,” Costa says. “Such information is distributed much faster and available to everyone across the internet.” The resulting surge of studies over the last two years has already been published in both scientific and beekeeping journals. Training sessions, workshops, and seminars on Tropilaelaps are also mushrooming across Europe and the United States.

“In beekeeping, and especially in honey bee parasite control, timing is everything,” Costa says. “With T. mercedesae now added to the equation alongside V. destructor, it is obvious that current mite management strategies will need to be redesigned.”

Carolyn Bernhardt, M.A., is a freelance science writer and editor based in Portland, Oregon. Email: [email protected].