Honey guide
Varroa Mite and British Beehives
Varroa is the most important parasite in British beekeeping. Here is how it spreads, why it is dangerous, and how UK beekeepers actually manage it.
By Honey Honey Honey · Published 3 June 2026
What is Varroa destructor and when did it arrive in Britain?
Varroa destructor is an ectoparasitic mite that lives on and reproduces inside the brood of honey bees. Originally a parasite of the Asian honey bee Apis cerana, it transferred to the western honey bee Apis mellifera — the species kept by British beekeepers — and spread globally through the movement of bee colonies during the twentieth century. It arrived in Britain in the early 1990s, first confirmed in southern England, and spread to virtually every managed colony in the country within a decade.
The mite is visible to the naked eye as a reddish-brown, oval speck approximately 1.5mm across. Adult females feed on developing bees inside sealed brood cells, where they also reproduce. Adult phoretic mites — those riding on adult bees rather than inside brood — can be seen on the bodies of bees during inspection, particularly under the abdomen or between body segments.
Before Varroa, British beekeeping operated without this parasitic pressure, and many practices now standard — seasonal monitoring, licensed treatments, autumn mite counts — did not exist. The pre-Varroa era is within the memory of older beekeepers but is not a realistic baseline to return to. The mite is permanently established in the British environment and is present in feral as well as managed colonies.
Its arrival transformed British beekeeping more than any other single event in modern times. It made treatment literacy a basic competency for all beekeepers, changed the economics of the activity, and drove significant investment in monitoring and control research.
How does the Varroa mite reproduce inside a hive?
A mated female Varroa mite enters a brood cell just before it is capped — typically a worker cell eight days after the egg is laid, or a drone cell ten days after the egg. She hides in the brood food beneath the developing larva. Once the cell is capped, she lays her first egg within approximately 60 hours. The first egg produces a male; subsequent eggs at roughly 30-hour intervals produce females.
The male mates with his sisters inside the sealed cell. On average, one to two mated daughter mites emerge from a worker cell alongside the adult bee; drone cells, capped for longer, may produce up to three mated daughters. The mother mite and her mated daughters ride out on the emerging bee as phoretic mites, then seek new brood cells to enter and repeat the cycle.
The reproduction rate means that a low mite population at the start of the active season can grow exponentially through the summer brood period. A colony with ten mites in April may have hundreds or thousands by August if not treated, because each mite can produce two new reproductive females per worker-bee cycle, and the colony is producing new brood continuously.
Drone brood is disproportionately attractive to mites because it is capped for longer — giving more time for reproduction — and drone cells are often produced at the colony periphery where mite detection is harder. This is why some management strategies involve drone brood removal as a way of trapping mites and reducing overall infestation.
Why does Varroa kill colonies rather than just weakening them?
Varroa kills colonies mainly by acting as a vector for viruses rather than through direct feeding damage alone. The mite punctures bee pupae and adults to feed on the fat body — the main nutrient store that fuels immune function, winter survival, and glandular activity. This direct damage impairs individual bees. But the more destructive effect is that Varroa transmits deformed wing virus and several other bee viruses between individuals and between generations of brood.
Deformed wing virus (DWV) was present in bee populations before Varroa but at low levels. Varroa amplifies DWV transmission dramatically by injecting it directly into developing pupae during feeding, bypassing surface immunity and allowing the virus to replicate in the fat body. Bees emerging from Varroa-infested cells have significantly elevated DWV titres and frequently show deformed wings, shortened abdomens, or impaired cognitive function even when wings appear normal.
The winter bee population is the most vulnerable. Winter bees reared in August and September in a high-Varroa colony are fat-body-depleted and virus-loaded before they even begin winter. They die earlier, thermoregulate less effectively, and fail to carry the colony to spring. This is why the classic Varroa-collapse pattern is a colony that looks acceptable in September but is dead or nearly dead by November.
Without treatment, the average untreated colony in Britain collapses within two to three years of initial Varroa infestation, depending on starting mite load and local reinfestation pressure from neighbouring colonies.
How do beekeepers monitor Varroa levels in a British hive?
The three main monitoring methods used by British beekeepers are the alcohol wash, the sugar roll, and the sticky board natural mite drop count. Each measures mite levels differently and has different precision.
The alcohol wash is the most accurate method. A sample of approximately 300 worker bees is collected from the brood area of the hive and placed in a jar with alcohol or soapy water. The sample is agitated, which detaches mites from the bees. The liquid is filtered and mites counted. The proportion of mites to bees gives an infestation rate, which is compared against treatment thresholds. A rate above 3% during the active season, or more than 1,000 mites on a sticky board wash in early autumn, are commonly cited action thresholds.
The sugar roll achieves the same mite separation using icing sugar instead of alcohol, allowing the bees to be released unharmed after counting. It is less precise than the alcohol wash because mites adhere less consistently to sugar than to alcohol, but it is preferred by beekeepers who object to sacrificing a sample of bees.
Sticky boards placed beneath a mesh floor collect mites that fall naturally from the colony. Counting the 24- or 48-hour mite drop gives an indication of infestation level but is less precise than wash methods because natural mite drop rates vary with season, colony size, and brood pattern. It is more useful for trend monitoring than for precise threshold decisions.
What licensed Varroa treatments are available to UK beekeepers?
The UK has several licensed Varroa treatments available to beekeepers without prescription. Oxalic acid is the most widely used and is licensed in multiple application formats. As a liquid drizzle, it is highly effective when applied during the winter broodless period because it kills phoretic mites on adult bees — typically achieving 90%+ knockdown in a single treatment. As a vapour, it can be applied through a capped hive entrance and works with or without brood present, though efficacy is reduced when brood is sealed. Oxalic acid does not taint honey and carries no harvest interval restriction in the formats licenced for use in the UK.
Apiguard is a thymol-based gel placed on top of the frames. Thymol vapour disperses through the hive at warm temperatures and reduces mite levels through contact and ingestion. It requires temperatures above 15°C to work effectively, making it a late-summer or early-autumn treatment. It has a honey harvest restriction — supers must be removed before treatment begins. It works with brood present, which makes it useful in late summer when colonies are still actively raising young.
Apivar contains amitraz-impregnated strips that are placed between brood frames for six to ten weeks. It is effective with brood present and achieves good knockdown, but it requires strict adherence to treatment duration and the avoidance of honey supers during treatment. There is also a risk of resistance developing in mite populations where amitraz is used repeatedly, which is why rotating between treatment types or combining organic acid and thymol strategies is recommended.
Can honey bees develop natural resistance to Varroa?
Some bees show traits that reduce mite reproduction or accelerate mite removal, and selective breeding for these traits is an active area of research and practical work among some British beekeepers. The most studied trait is VSH — Varroa-sensitive hygiene — in which bees detect and remove mite-infested pupae from sealed cells before mite reproduction is completed. VSH bees at high expression can suppress mite population growth substantially.
A second trait is recapping, where bees unseal and reseal capped cells when they detect problems, including mite presence. A third is increased grooming behaviour — bees that more actively brush and bite mites from each other's bodies carry lower phoretic mite loads. All three behaviours exist in the general Apis mellifera population at low frequency and can be selected for through breeding.
In practice, developing colonies with genuinely useful mite resistance through selective breeding requires consistent selection across multiple generations, access to queens of known VSH-expressing stock, and controlled mating that is very difficult in Britain's open mating environment. A few UK breeders work with imported VSH stock or through local selection programmes, but resistant bees remain a small minority of the overall UK population.
Truly self-sustaining Varroa-resistant populations of Apis mellifera exist — notably on Gotland island in Sweden and in parts of the Arnot Forest study population in the US — but these arose through decades of natural selection on isolated feral populations, not through managed breeding in active apiaries.
What role does Varroa play in British winter colony losses?
Varroa is a direct contributor to winter losses in the UK even when the immediate cause of death appears to be starvation or cold. The mechanism is the impairment of winter bees described above: mite feeding and virus loading during August and September reduces the quality and lifespan of the bees responsible for carrying the colony through winter. A colony with high mite levels in September enters October already compromised.
National monitoring programmes including the BBKA annual spring survey consistently show that Varroa management quality correlates with winter loss rates. Beekeepers who treat at the recommended times, monitor counts before and after treatment, and use effective products report lower losses than those who treat rarely or not at all. This is not a surprising finding, but it confirms that Varroa management is one of the most controllable variables in overwintering success.
Autumn treatment timing is the single most impactful decision a beekeeper makes each season. Treating too late — after the winter bee generation is already being reared in virus-laden conditions — leaves the colony with damaged bees regardless of how good the treatment knockdown is. The window for effective pre-winter treatment is typically late July to early September, after honey supers are removed and before the critical winter bee cohort is capped.
Winter Varroa treatment with oxalic acid during the broodless period in December or January adds a further mite reduction before the spring build begins, and is standard practice in well-managed apiaries.
Is there any prospect of Varroa-free beekeeping returning to the UK?
There is no realistic prospect of eliminating Varroa from the UK bee population in the near future. The mite is present in feral colonies throughout the country and cannot be eradicated through treatment of managed hives alone. Any unmanaged colony serves as a reservoir, and reinfestation of treated hives through robbing and drifting behaviour occurs continuously in areas with moderate bee density.
Research directions that could change the long-term outlook include gene drive technologies aimed at suppressing mite reproduction, RNA interference approaches that target Varroa-specific pathways, and accelerated selective breeding programmes for VSH traits in British bees. None of these is close to widespread practical deployment, and all face regulatory, ecological, or logistical barriers in a UK context.
The Varroa-free island populations that exist in the world — the Northern Isles of Scotland including Colonsay, and a few other isolated locations — are maintained through import restrictions and geographic isolation. Colonsay's native bee population and its Varroa-free status are protected by a statutory Order restricting bee imports to the island. This is a viable model for small isolated populations but cannot scale to mainland Britain.
The practical reality for British beekeeping is that Varroa management is a permanent feature of the activity, requiring ongoing monitoring, timely treatment, and intelligent strategy rather than any expectation of resolution. The beekeepers who achieve consistently good results are those who treat Varroa as a management discipline rather than a problem to be solved once.
Frequently asked questions
- What is Varroa?
- Varroa destructor is a parasitic mite that attacks honey bees.
- Can a colony survive without treatment?
- Some can for a while, but many unmanaged colonies collapse under viral pressure.
- Do mites feed on bee blood?
- Modern research shows they feed primarily on the bee fat body rather than simple haemolymph alone.
- When do UK beekeepers treat for Varroa?
- Often after summer honey removal and sometimes again in broodless winter periods, depending on counts and system.
- Is Varroa linked to deformed wing virus?
- Yes. That viral association is one of the main reasons the mite is so damaging.