“We kept hearing anecdotally that these Californian honeybees were surviving with way fewer treatments. I wanted to test them rigorously and understand the driving force behind what the beekeepers were seeing,” said Genesis Chong-Echavez, a UCR graduate student and lead author of the study, in an article from the university.

WHY IT MATTERS: Varroa mites can devastate Canadian beekeepers’ hives, and go-to control methods have become less effective, leading producers to look for new methods to protect honeybees.

Varroa mites are an invasive parasite that has plagued North American beekeepers since the late 1980s. The mites weaken the bees by feeding on their fat stores, and also can carry viruses. Varroa mites are a consistent contender among the top four causes of winter bee loss in Canada, as noted by the Canadian Association of Professional Apiculturists.

Chong-Echavez’s team found bee colonies led by locally-raised Californian hybrid honeybee queens had about 68 per cent fewer mites, on average, than hives with commercial queens.

While these populations were not entirely varroa mite-free, they were more than five times less likely to hit the threshold at which chemical treatment is necessary.

Local bee larvae attract fewer mites

The resistant bees came from a genetically-mixed population established in southern California — often from “feral” colonies living in trees, the UC Riverside article said. They were found to have mixed ancestry steming from African, eastern European, Middle Eastern and western European genetics.

Varroa mites must enter bee brood cells to reproduce. In lab experiments with developing honeybee larvae, researchers found mites were less attracted to the locally-adapted bees than commercial bees.

“What surprised me most was the differences showed up even at the larval stage,” Chong-Echavez said. “This suggests the resistance mechanism may go deeper than some kind of behaviour and may be genetically built into the bees themselves.”

The research team next intends to investigate the signals that may make the locally-adapted larvae less attractive to mites.

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“We are very concerned about another mite coming in with the potential to totally devastate our industry and cause significant problems,” said Peter Awram, director of the Canadian Beekeeping Federation.

The federation called a press conference in Ottawa on Tuesday to highlight the rise of the tropilaelaps mite (colloquially referred to as the “t-mite”).

The t-mite – which feed on developing bees and serve as a vector for viruses — has not yet been detected in Canada. However it’s been reported in Russia, throughout Asia and in Papua New Guinea. Papau New Guinea is 93 kilometres away from major bee trade partner Australia. Bee experts also warn the mite is headed for Europe.

Awram said the combination of the t-mite and the varroa mite – presently the industry’s most destructive disease pest — would be calamitous.

“We’ve already been suffering considerable problems with bee health because of our long winters,” he said. “A lot of it is in relation to another mite that’s been here for some time, but we are seeing massive bee losses overnight.”

Keeping the t-mite out of Canada

Keeping the mite out of Canada may require limiting trade exposure to infected countries. Alberta Beekeepers Commission President Curtis Miedema called on the federal government to prioritize policy that could help stem this tide.

“We’re hoping to see the government intervene and stop the imports of bees from offshore,” Meidema said. “We feel like North America needs to become a stronghold and keep this mite out.”

Peace River-Westlock MP Arnold Viersen has brought a motion to Parliament to address t-mites and a range of other trials facing beekeepers. He said the U.S. is already testing for the mite and searching trade vessels such as container ships.

“We’re hoping that the Canadian government can do something similar: monitor for it and work with the Americans so that we can keep this mite out of North America,” he said.

The motion proposes to restore free trade for honey bee package imports from regional safe zones in the U.S., to prepare an emergency response plan for t-mite, and other measures.

Vierson suggested the development of a North American bee strategy that would coordinate U.S. and Canadian efforts.

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From Asia to Europe

Tropi’s natural host is the giant honey-bee (Apis dorsata), common across South and Southeast Asia. At some point, the mite jumped to the western honey-bee (Apis mellifera), the species kept by beekeepers around the world. Because this host is widespread, the parasite has steadily moved westwards.

It has now been detected in Ukraine, Georgia and southern Russia, and is suspected to be in Iran and Turkey. From there, it is expected to enter eastern Europe, then spread across the continent. Australia and North America are also at risk.

Why tropi spreads so fast

Like varroa, tropi is a tiny mite that breeds inside capped brood cells, the life stages of the honey-bee when the late larvae and pupae develop inside honeycomb cells that are sealed by a layer of wax. The mite feeds on bee pupae and transmits lethal viruses, such as deformed wing virus – the deadliest of the bee viruses. But there are crucial differences.

Varroa can survive on adult bees for long periods, but tropi cannot. Outside brood cells, it lives only a few days, scurrying across the comb in search of a new larva.

Because tropi spends more time in capped cells, it reproduces quickly. A capped cell that contains a female varroa will result in one or two mated varroa offspring emerging with the adult bee. Tropi offspring develop faster inside a capped cell than varroa offspring, so a tropi “mother” may result in more offspring emerging than a varroa infested cell, more quickly overwhelming the colony.

As a result, colonies infested with tropi can collapse far faster than those plagued by varroa.

Current control methods

In parts of Asia where the parasite is already established, small-scale and commercial beekeepers often manage it by caging the queen for about five weeks.

With no eggs being laid, no brood develops, leaving the mites without a food source. This method is practical where beekeepers manage dozens of hives, but not in places like Europe where commercial operations often involve thousands.

Another option is treating the beehive with formic acid, which penetrates brood cell caps and kills the mite without necessarily harming the developing bee, provided concentrations are kept low. This treatment may offer beekeepers a practical tool.

Why varroa treatments won’t work

Many wonder whether the chemicals used against varroa could also fight tropi. The answer is, mostly no.

Varroa spends much of its life outside of a capped cell clinging to adult bees, where it comes into contact with mite-killing chemicals known as miticides spread through the colony on bee bodies. By contrast, tropi rarely attaches to adults, instead darting across comb surfaces.

Because of this, it is far less exposed to chemical residues. Treatments designed for varroa are often ineffective against the faster-breeding tropi.

Managing both mites together will be particularly difficult. Combining treatments risks harming colonies or contaminating honey. For instance, formic acid for tropi and insecticides such as amitraz for varroa might interact at even low levels, killing the bees as well as the parasites.

There is also the danger of resistance. Over-use of varroa treatments has already produced resistant strains, reducing the effectiveness of several once-reliable chemicals. Introducing more compounds to fight tropi, without careful integrated pest management, could accelerate this process and leave beekeepers with few effective tools.

The wider impact

The spread of tropi will not only devastate beekeepers but also agriculture more broadly. Honey-bees are critical pollinators of many crops. Heavier hive losses will raise costs for both honey production and pollination services, affecting food prices and availability.

Research is underway in countries such as Thailand and China to develop better management strategies. But unless effective and practical treatments are found soon, the spread of this new mite around the world could be catastrophic.

The story of varroa shows how quickly a single parasite can transform global beekeeping. Tropi has the potential to be even worse: it spreads faster, kills colonies more quickly, and is harder to control with existing methods.

— Jean-Pierre Scheerlinck is an honorary professor fellow at Melbourne Veterinary School at the University of Melbourne. The author would like to acknowledge the contribution of Robert Owen, a beekeeper who completed a PhD on the varroa mite at the University of Melbourne in 2022, to this article.

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In late 2024, the agency opened the door to potential risk mitigation suggestions, following a push from some corners of the beekeeping sector. While still contentious among honey producers, several beekeeping organizations had been pushing for the CFIA to again allow packaged bee imports from the U.S., citing significant winter losses, difficultly in sourcing replacement stock and new knowledge gained since the last official full risk assessment back in 2013.

U.S. packaged bees haven’t been allowed into Canada since the ’80s due to issues such as resistant American foulbrood, small hive beetle, varroa mites and Africanized genetics.

The CFIA’s consultation ended Jan. 31, 2025.

In a recent summary document, the CFIA said that, after analyzing the submitted risk mitigation proposals, the measures would be insufficient.

“The CFIA does not have a duty of care to protect the economic interests of stakeholders,” the document read. “The CFIA’s regulatory mandate under the Health of Animals Act and regulations is to help protect Canadian animal health, which includes the health of the Canadian honey bee population.”

Submissions included a suggested limited regional trade strategy, an evaluation of the impact on inter-provincial movement, a pilot project to import from Northern California, risk mitigation for all identified hazards, transport inspections upon entering Canada, using current import conditions of queens for the importation of packages and the utilization best management practices post-importation.

The CFIA’s comprehensive import risk analysis “clearly demonstrated scientifically” the risks the proposals presented, read the agency response, which is available on the CFIA website.

In several cases, the CFIA noted, proposals had to do with further research rather than active risk mitigation measures. Others, the agency dismissed as lacking in robust scientific backing or said they did not properly address the risk in question.

Glacier FarmMedia will be following up on this story in following weeks.

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