The Latest on Varroa Mites – What We Now Know – 2025

Varroa mites, those tiny but mighty parasites, have become a persistent problem for beekeepers worldwide. These mites latch onto honeybees, sucking their blood and weakening entire colonies. As we continue to learn more about these pests, new strategies and insights emerge to help us manage and mitigate their impact. Understanding the latest developments is crucial for anyone involved in beekeeping, whether you’re a hobbyist or a commercial operator.

In this article, we’ll take a quick look at the world of Varroa mites, skimming the most recent research and findings. We’ll cover their biology, the latest treatment methods, and how you can keep your hives healthy.

What Are Varroa Mites and Why Are They a Problem?

Understanding the Varroa Destructor

Varroa mites, scientifically known as Varroa destructor, are external parasitic mites that attack honeybees. They are one of the most significant threats to beekeeping globally today. But why are they such a problem?

These mites feed on the fat bodies of bees, which are crucial for their immune system and overall health. By weakening individual bees, Varroa mites can lead to the collapse of entire colonies if not managed effectively. They also spread viruses, exacerbating their harmful effects.

Lifecycle and Behaviour

Understanding the lifecycle and behaviour of Varroa mites is key to managing them effectively. Here’s a quick rundown:

Reproduction: Varroa mites reproduce in the brood cells of honeybees. A female mite enters a cell just before it is capped, laying eggs that hatch and develop alongside the bee pupa.
Feeding: Both adult and juvenile mites feed on the fat bodies of bees. This feeding damages the bees and transmits viruses.
Spread: Mites move between bees through direct contact, often during foraging or hive robbing. This makes them highly contagious.

How Have Our Understanding and Strategies Evolved?

Advancements in Research

Recent research has significantly advanced our understanding of Varroa mites and how to combat them. Scientists have been studying their biology, genetic makeup, and behaviour to find weaknesses that can be exploited. For example, researchers have discovered that Varroa mites have specific genes that can be targeted to disrupt their lifecycle.

Integrated Pest Management (IPM)

One of the most promising developments is the use of Integrated Pest Management (IPM) strategies. IPM involves using a combination of biological, mechanical, and chemical methods to control Varroa mite populations. Here are some key components:

Biological Control: Introducing mite-resistant bee strains and beneficial microorganisms that can naturally reduce mite populations.
Mechanical Control: Techniques like drone brood removal, where drone brood (which mites prefer) is periodically removed and destroyed, thereby reducing mite numbers.
Chemical Control: Using miticides carefully and selectively to avoid resistance build-up.

What Are the Latest Treatment Options?

Chemical Treatments

While chemical treatments are still widely used, there are new developments in this area aimed at making them more effective and less harmful to bees. Some of the latest options include:

Organic Acids: Treatments like oxalic acid and formic acid have gained popularity due to their effectiveness and lower risk of resistance. They can be used during broodless periods when mites are more exposed.
Essential Oils: Thymol, derived from thyme oil, has shown promise in controlling Varroa mites. It’s used in various formulations that are applied directly to the hive.

Biotechnical Methods

Biotechnical methods focus on manipulating bee behaviour and hive conditions to control mite populations. Some innovative approaches include:

Heat Treatment: Applying heat to hives can kill Varroa mites without harming bees. This method requires careful control to ensure effectiveness.
Brood Interruption: Temporarily halting the queen’s egg-laying disrupts the mite’s reproductive cycle, reducing their numbers.

What Role Do Genetics Play in Combating Varroa Mites?

Breeding for Resistance

One of the most exciting areas of development is breeding bees that are naturally resistant to Varroa mites. Some bee strains have shown a natural ability to detect and remove mites from their bodies and brood cells, a behaviour known as Varroa Sensitive Hygiene (VSH).

VSH Bees: Bees with VSH traits actively remove infested brood, disrupting the mite’s lifecycle. Breeding programs aim to enhance these traits in bee populations.
Hybrid Bees: Crossing resistant strains with local bees can introduce desirable traits while maintaining local adaptation.

Genetic Research

Genetic research has also uncovered specific genes associated with mite resistance. By understanding these genetic markers, beekeepers and scientists can work together to select and breed bees with enhanced resistance.

How Can Beekeepers Implement These Strategies?

Practical Tips for Beekeepers

Implementing the latest strategies requires a combination of knowledge, vigilance, and adaptation. Here are some practical tips for beekeepers:

Regular Monitoring: Keep a close eye on mite levels using methods like sugar rolls or alcohol washes. Regular monitoring helps in early detection and timely intervention.
Diverse Approaches: Use a combination of methods tailored to your specific conditions. This might include biotechnical methods, selective chemical treatments, and breeding for resistance.
Education and Training: Stay informed about the latest research and techniques. Join local beekeeping associations and participate in workshops and training sessions.

Community and Collaboration

Beekeeping is not just an individual activity; it thrives on community collaboration. Sharing knowledge and resources with fellow beekeepers can significantly enhance your ability to manage Varroa mites effectively.

What Does the Future Hold?

Ongoing Research and Innovations

The fight against Varroa mites is ongoing, with researchers continuously seeking new solutions. Innovations such as RNA interference (RNAi) to target mite genes and advanced breeding techniques hold promise for the future.

Sustainable Practices

The goal is to develop sustainable practices that reduce dependency on chemical treatments and enhance the natural resilience of bee populations. This holistic approach benefits not only beekeepers but also the broader ecosystem.

Fighting Varroa Mites: A Collaborative Effort for a Sustainable Future

In conclusion, Varroa mites remain one of the most formidable challenges in beekeeping. However, advancements in research and the adoption of integrated pest management strategies provide hope and practical solutions. By understanding the biology of these mites, embracing innovative treatments, and fostering collaboration within the beekeeping community, we can create a sustainable future for our bees.

Varroa mites may be a persistent problem, but with the right knowledge and strategies, beekeepers can manage their impact effectively. Stay informed, be proactive, and continue to adapt your practices to ensure the health and vitality of your hives. Together, we can build a resilient and thriving beekeeping community.

2025 Update: Critical Developments in Varroa Mite Management

Since our original article was published, the landscape of Varroa mite management has shifted dramatically. The 2024-2025 season brought unprecedented challenges alongside groundbreaking innovations. This update covers the most significant developments that every beekeeper needs to understand.

The Scale of the 2024-2025 Colony Losses

Data from the Honey Bee Health Coalition revealed staggering losses during the 2024-2025 season. Between June 2024 and March 2025, beekeepers reported losing approximately 1.7 million colonies, with commercial operations sustaining an average loss of 62%. USDA researchers attribute these unprecedented losses to a combination of factors, with amitraz-resistant Varroa mites and the viruses they transmit identified as primary culprits.

In June 2025, USDA-ARS scientists confirmed that high levels of deformed wing virus A and B, along with acute bee paralysis, were present in virtually all sampled bees from collapsed colonies. The mites spreading these viruses showed signs of resistance to amitraz in nearly all samples tested, representing a fundamental shift in the Varroa management landscape.

The Amitraz Resistance Crisis

For decades, Amitraz (sold under brand names like Apivar) has been the workhorse of Varroa control, particularly for commercial operations. Unlike other synthetic acaricides that quickly lost effectiveness due to resistance, amitraz maintained its efficacy far longer than expected. That era appears to be ending.

Understanding the Genetic Mechanisms

Research teams across the globe have identified multiple mutations associated with amitraz resistance:

Y215H mutation: First identified in Spanish populations, this mutation in the β2-octopamine receptor has been confirmed in mite populations across North America and Europe.
F290L mutation: A second mutation in the octopamine receptor, also associated with treatment failures, confirmed in Spanish populations in late 2024.
T115N mutation: A novel mutation identified in Korean populations in 2025, which spread rapidly through mite populations within just five years.

Research published in January 2025 confirmed amitraz-resistant mites in Canadian populations, with bioassay results from Alberta showing clear evidence of resistance evolution. Similar findings have emerged from studies in the UK and across Europe.

Implications for Irish and UK Beekeepers

While resistance levels vary by region, the UK National Bee Unit’s updated 2025 guidance now explicitly advocates for thymol and organic acids as preferred treatments, moving away from synthetic miticides. This shift recognises both the growing resistance problem and the benefits of rotating treatment classes to prevent further resistance development.

Breakthrough: RNA-Based Mite Control

Perhaps the most significant development of 2025 is the EPA’s registration of Norroa (active ingredient: Vadescana), the first RNA interference (RNAi) treatment specifically designed for Varroa mites. Developed by GreenLight Biosciences, this represents an entirely new mode of action in mite control.

How RNAi Technology Works

RNA interference uses double-stranded RNA (dsRNA) to prevent the expression of specific genes essential for mite survival. When applied to hives, the treatment is deposited in brood cells where Varroa foundresses lay their eggs. The hatched mite offspring consume the RNA, which stops them from developing and latching onto bees.

Key advantages of this approach include:

Extended control: Field trials demonstrated mite control for up to 18 weeks, substantially longer than existing products.
High specificity: The treatment targets Varroa-specific genes and has no effect on bees, humans, other insects, or the environment.
Temperature flexibility: Can be applied at any temperature when it’s safe to open the hive, unlike many organic treatments.
Colony safety: No negative impacts on brood, workers, or queens were observed in trials.

Important note: Norroa is designed as a preventative treatment, best applied when mite levels are low. It maintains low mite populations rather than rescuing colonies already overwhelmed by mites. This makes regular monitoring essential.

Advances in Biological Control: Fungal Biopesticides

Researchers at Washington State University have made significant progress in developing a heat-tolerant strain of the mite-killing fungus Metarhizium brunneum. The challenge with fungal biocontrol has always been that beehive temperatures (around 35°C) are too warm for most fungal strains to thrive.

Through directed evolution, the team increased spore germination at hive temperatures from 44% to 70%. When tested against oxalic acid in 30 colonies, the evolved fungus proved equally effective at controlling mite populations over 18 days. The fungus works by landing on mites and germinating spores that drill through the mite’s exoskeleton, eventually killing it.

While not yet commercially available, this research represents a promising non-chemical alternative that could complement existing treatment strategies.

The Critical Importance of Treatment Timing

A landmark study from the University of Exeter, published in February 2025, revealed that more than a third of beekeepers in England and Wales deviate from recommended treatment guidelines, including application windows. The research found that beekeepers who mistimed their Varroa treatments experienced significantly higher colony losses, regardless of which treatment they used.

Dr Thomas O’Shea-Wheller, lead author of the study, noted that this finding suggests a major cause of honeybee mortality could be relatively easy to reduce through better adherence to treatment schedules. The key periods requiring attention are:

Late summer/autumn: Ensuring colonies enter winter with low mite loads to prevent virus transmission during the broodless period.
Late winter/early spring: Preventing mites from having a large launching pad for exponential growth as the colony begins brooding.

Rethinking Integrated Pest Management: The Immigration Factor

A February 2025 paper published in Current Opinion in Insect Science presents a novel approach to understanding Varroa population dynamics. The researchers argue that how mite numbers increase within a colony—whether through in-hive reproduction (chronic phase) or immigration from other colonies (acute phase)—should determine which management techniques are most effective.

Control methods that reduce reproduction rates work best during the chronic phase, while understanding when and how mites enter hives (the acute phase) may enable existing bee management techniques to be repurposed for Varroa control. This perspective emphasises that in-hive control will be improved by better understanding the behavioural ecology of how and when Varroa enter hives.

Improving Organic Treatment Efficacy

Research published in early 2025 has explored the use of adjuvants—compounds typically used in agricultural pesticides to improve spreading and penetration—to enhance the effectiveness of oxalic acid treatments.

Field trials using oxalic acid combined with a bee-safe adjuvant in glycerin-soaked strips showed significantly better results than oxalic acid alone. The adjuvant not only improved efficacy but also increased the speed of the miticidal effect. This research could lead to improved formulations of existing organic treatments, giving beekeepers more effective tools that don’t contribute to resistance problems.

Progress in Varroa-Resistant Bee Breeding

The push towards breeding naturally Varroa-resistant bees continues to gain momentum, particularly in Ireland and the UK.

Irish Initiatives

The Native Irish Honey Bee Society (NIHBS) continues its Varroa tolerance breeding programme, working to improve the health and survivability of the native Irish bee (Apis mellifera mellifera) through selective breeding for mite-resistant traits. PhD students at both the University of Galway and the University of Limerick are analysing samples collected from across Ireland. Professor Grace McCormack at NUI Galway has been investigating the survival, diversity, and distribution of free-living (untreated) colonies, studying their resilience to Varroa.

Ireland’s Apis mellifera mellifera population is considered the purest in the world, making it a valuable genetic resource. If Varroa-tolerant traits can be selected from within this native population, it would represent significant progress for sustainable beekeeping.

UK Treatment-Free Successes

Westerham Beekeepers in south-east England are now in their ninth year of not using miticide treatments, demonstrating that treatment-free approaches can work when combined with careful selection for resistant traits. A UK-wide survey found that approximately 6% of beekeepers (around 1,800) have been treatment-free for six years or more, with treatment-free practitioners distributed throughout England.

The mechanisms these resistant bees use include Varroa Sensitive Hygiene (VSH), where bees detect and remove infested brood at the pink-purple eyed pupal stage, stopping mite reproduction before offspring mature. This behaviour provides three benefits: no mite reproduction, death of immature mite offspring, and reduced reproductive capacity of foundress mites.

Emerging Threat: Asian Hornet Reaches Ireland

While Varroa remains the primary threat, Irish beekeepers must now also be aware of the Asian hornet (Vespa velutina). Through the Shared Island Biosecurity and Invasive Species Initiative, Ireland developed a contingency response plan that was activated in 2025 when incursions were detected. The National Biodiversity Data Centre’s Invasive Species Programme continues to monitor and respond to this threat.

Updated Recommendations for Beekeepers

In light of these developments, here are updated recommendations:

Monitor regularly: Use alcohol washes or sugar rolls to assess mite levels. The 3% infestation threshold remains the point at which intervention is warranted.
Rotate treatments: Alternate between different modes of action annually to slow resistance development. Consider organic acids (oxalic, formic) and thymol-based treatments alongside any synthetic options.
Time treatments correctly: Follow label instructions precisely. Late summer/autumn and late winter/early spring are critical periods.
Coordinate with neighbours: Mites from collapsing colonies will re-infest nearby hives. Treating in coordination reduces reinfestation pressure.
Select for resistance: Retain colonies that show natural resistance traits for queen-rearing. Look for evidence of hygienic behaviour and low mite loads despite limited treatment.
Stay informed: New treatments and resistance patterns are evolving rapidly. Engage with your local beekeeping association and attend workshops to stay current.
Watch for new treatments: RNA-based treatments like Norroa may become available in Ireland and the UK pending regulatory approval. These offer a genuinely new mode of action that could be valuable additions to IPM strategies.

Looking Ahead

The 2024-2025 season served as a stark reminder that Varroa management cannot be taken for granted. The emergence of widespread amitraz resistance, while concerning, has also accelerated innovation in treatment options and renewed interest in breeding naturally resistant bees.

The arrival of RNA-based treatments represents the most significant advance in Varroa control technology in decades. Combined with improvements in organic treatment formulations, fungal biopesticides in development, and growing populations of naturally resistant bees, there are genuine reasons for optimism.

However, no single solution will solve the Varroa problem. Success requires an integrated approach: regular monitoring, properly timed treatments using rotating modes of action, coordination with neighbouring beekeepers, and selection for resistant genetics. The beekeepers who thrive will be those who stay informed, adapt to new developments, and implement best practices consistently.

For the latest guidance, consult the FIBKA guidelines at https://irishbeekeeping.ie/fibka-guidelines-on-varroa-destructor/ and the UK National Bee Unit’s resources at www.nationalbeeunit.com.

— Article update published February 2026 —