Managing Varroa Mites: A Complete Guide for Beginner Beekeepers

Introduction

If you’re new to beekeeping, one of the first challenges you’ll encounter is managing Varroa destructor, a parasitic mite that threatens the health and survival of honey bee colonies. Since its arrival in the UK in 1992, Varroa has become the single most serious problem facing beekeepers. Left unmanaged, it can destroy a colony within just a few years.

This comprehensive guide explains what Varroa mites are, how to identify and monitor infestations, and the most effective ways to control them using an integrated, practical approach suitable for new beekeepers.

What Is Varroa Destructor?

Varroa destructor is a small external parasite that feeds on the bodies of honey bees. Although barely visible to the naked eye, its impact on colonies is immense. Originally found on the Asian honey bee (Apis cerana), Varroa jumped to the European honey bee (Apis mellifera) during the 20th century. The European species has few natural defences against the mite, making control essential for every beekeeper.

A female Varroa mite appears as a reddish-brown oval about 1.6 mm long. Males and immature females are smaller and found only inside sealed brood cells.

Why Varroa Is a Problem

Varroa mites harm bees in two major ways:

1. Feeding Damage – The mites puncture the bee’s body and feed on its fat tissues, weakening both adults and developing brood.
2. Virus Transmission – They act as carriers for deadly bee viruses, especially Deformed Wing Virus (DWV), which causes wing deformities and premature death.

An untreated infestation often leads to Parasitic Mite Syndrome – a fatal combination of viral disease, weakened brood, and colony collapse. Even strong colonies can collapse within weeks once mite levels exceed a critical threshold.

Where Varroa Is Found

Today, Varroa mites are found across nearly all of the UK, except for the Isle of Man, the Isles of Scilly, and a few remote Scottish islands. Because of this, every beekeeper must assume their colonies are at risk and should routinely monitor and manage Varroa.

Recognising Varroa in Your Hive

The early signs of Varroa can be subtle, so close inspection is key. Look for:

• Tiny reddish-brown mites on adult bees or brood.
• Bees with deformed wings or shortened abdomens.
• Irregular brood patterns (“pepperpot” appearance).
• Bald brood where cappings have been nibbled away.
• A sudden decline in adult bee population.

If you see several of these symptoms, your colony may be heavily infested and require immediate action.

Understanding Varroa Biology

To manage Varroa effectively, it helps to understand its life cycle:

1. A mature female mite enters a bee brood cell just before it’s capped.
2. Once sealed inside, she begins feeding and laying eggs on the developing bee.
3. The first egg hatches into a male, followed by several females.
4. Mating occurs inside the cell before the bee emerges.
5. The mature females leave with the emerging bee to find new cells.

This entire cycle lasts about 10 days in worker brood and slightly longer in drone brood – which Varroa prefer, as it gives them more time to reproduce. Mite numbers can increase 10- to 800-fold over a single season if left unchecked.

Monitoring Varroa: Know Before You Treat

Monitoring helps you track infestation levels and decide when to treat. It should be done at least four times per season – in early spring, after the spring flow, post-harvest, and late autumn.

1. Natural Mite Drop (Sticky Board Method)

Place a sticky board or oiled tray beneath an open mesh floor for seven days, then count the fallen mites.

• Multiply daily mite drop by:
  • 30 (May–Aug),
  • 100 (Mar, Apr, Sep, Oct),
  • or 400 (Nov–Feb).
    If estimates exceed 1,000 mites per colony, treatment is essential.

Pros: Non-intrusive, simple to perform
Cons: Takes several days, approximate results

2. Drone Brood Uncapping

Remove and inspect 100–300 capped drone cells with an uncapping fork.
If more than 5–10% of pupae have mites, treat immediately.

Pros: Fast and accurate during drone season
Cons: Destroys brood, limited to spring–early summer

3. Alcohol Wash or Sugar Roll

Collect ~300 bees from a brood frame. In the alcohol wash, mites are dislodged and counted; in the sugar roll, powdered sugar shakes them free without killing bees.
If more than 5 mites per 100 bees (5%) are found, the colony needs treatment.

Pros: Accurate, quantitative
Cons: Alcohol wash kills sample bees; sugar roll less reliable in damp weather

Controlling Varroa: Integrated Pest Management (IPM)

Because Varroa can’t be eradicated, the goal is to keep mite populations below harmful levels using an Integrated Pest Management (IPM) approach. IPM combines regular monitoring, hygienic husbandry, and judicious use of approved treatments.

1. Good Beekeeping Practices

• Use open mesh floors to let fallen mites drop through.
• Avoid transferring infested combs between colonies.
• Replace old brood combs regularly to reduce mite hiding places.
• Requeen from resistant or hygienic stock when possible.

2. Husbandry Methods (Non-chemical Control)

These techniques exploit the mite’s reliance on brood for reproduction.

Drone Brood Removal:
Varroa prefer drone cells. Encourage bees to build drone comb, then remove and destroy it once capped. This can reduce mite numbers by up to 50%.

Comb Trapping (Queen Caging):
Confine the queen to a single frame for 9 days, rotate to a new frame twice more, then remove and destroy the infested brood combs. Combining this with an oxalic acid treatment after the final brood break can achieve very high control levels. Richard Noel from Bees in Brittany uses queen trapping.

Artificial Swarm:
Splitting colonies as part of swarm control can interrupt the brood cycle and temporarily halt mite reproduction.

While effective, these methods are time-sensitive and should be used primarily in spring and early summer.

3. Using Varroacides (Medicinal Control)

Approved varroacides are veterinary medicines tested for safety and efficacy. Always use UK-authorised products according to label instructions.

Common authorised treatments include:

Important legal points:

• Use only approved varroacides. “Homemade” formulations are illegal.
• Keep records of all treatments (product name, date, dose, batch number) for at least 5 years.
• Never treat during a honey flow unless the label allows it.
• Dispose of used materials safely – never down drains or in recycling.

Preventing Resistance

Mites can become resistant to synthetic treatments if they’re overused. To reduce this risk:

• Rotate products with different active ingredients.
• Combine chemical treatments with physical or biological methods.
• Never use expired or off-label products without veterinary advice.

At present, no resistance has been confirmed for thymol, formic acid, or oxalic acid, making these good long-term options.Living With Varroa: Long-Term Strategy

Even well-managed colonies will never be entirely mite-free. The key to success is monitoring, prevention, and strategic treatment. Over time, you’ll learn to integrate Varroa control naturally into your beekeeping calendar.

Key habits to develop:

• Stay updated via BeeBase, where you can register your colonies and access guidance from the National Bee Unit.
• Record all monitoring and treatment results.
• Check colonies more frequently after nearby collapses (mite invasion can spike).
• Aim to start each spring with the lowest possible mite levels.

Understanding Bald Brood and Uncapping Behaviour

Bald brood describes areas of sealed worker brood where the wax cappings have been removed, leaving patches of exposed, developing pupae. Traditionally, this was viewed as a sign of wax moth damage or poor brood hygiene, but modern research shows that bald brood can also indicate hygienic behaviour by the bees themselves. When honey bees detect diseased, parasitized, or otherwise unhealthy brood – often due to Varroa mite infestation beneath the cappings – they may uncap or even remove the affected pupae to prevent the spread of pathogens and mites. This process, known as Varroa-sensitive hygiene (VSH), is a valuable natural defence trait. Colonies displaying regular, symmetrical bald brood patches without extensive brood loss are often demonstrating this hygienic response rather than a problem. However, irregular or extensive bald brood, particularly in lines across the comb, can still result from wax moth tunnelling or other mechanical disturbances. Understanding the difference helps beekeepers recognise when their bees are actively managing Varroa rather than suffering from pest damage – and such colonies are worth selecting from in breeding programmes for long-term, sustainable mite resistance.

A Sustainable Beekeeping Perspective

While managing Varroa is vital, the long-term solution lies not in endless chemical treatments but in nurturing locally adapted, resilient bee populations. Research from across Europe shows that colonies derived from local genetic stock survive longer and adapt better to regional conditions than imported bees. Isolated studies in Gotland and other regions have even demonstrated natural co-adaptation between bees and Varroa when selection is allowed to operate without continual chemical intervention. This principle underpins Darwinian or sustainable beekeeping, where beekeepers work with natural selection rather than against it. By selecting queens from colonies that thrive untreated and overwinter successfully, we help build true Varroa tolerance over time. As Dr. Dorian Pritchard noted, progress in bee improvement comes from steady selection within a consistent gene pool, not from repeated cross-breeding or importation. Sustainable beekeeping, therefore, means committing to your local bees – particularly the native dark honey bee (Apis mellifera mellifera), whose unique adaptations to our northern climate are irreplaceable. Supporting these populations not only strengthens colony health and self-sufficiency but also protects our ecological heritage. As Willie Robson wisely observed, “Honeybees are not machines” – they need good husbandry, healthy nutrition, and the freedom to express their natural resilience.

https://www.nationalbeeunit.com/assets/PDFs/3_Resources_for_beekeepers/Advisory_leaflets/APHA_Managing_Varroa_2020_ELECTRONIC_ONLY-1.pdf