Varroa mite
The single biggest threat to a kept honeybee colony worldwide — a tiny external parasite that both weakens bees directly and spreads other bee viruses while it feeds.
- Cause
- Varroa destructor (external mite)
- Breeds in
- Sealed brood cells
- Also spreads
- Deformed wing virus
- Control
- Miticide + brood break
Overview
Varroa destructor is a reddish-brown external mite, just visible to the eye, that attaches to adult honeybees and feeds on their fat body, and reproduces inside sealed brood cells where it feeds on developing larvae and pupae. A colony can look normal for a long time while mite numbers quietly build up in the background, which is why regular checking matters more than waiting for obvious signs.
Damage comes two ways: directly, mite feeding weakens and shortens the life of both developing and adult bees; indirectly, and often more seriously, varroa transmits and amplifies honeybee viruses (particularly deformed wing virus) as it moves between bees and brood cells. This combination is what makes an unmanaged infestation capable of collapsing a colony within a season or two, especially heading into a dearth period or winter.
Because varroa reproduces inside the sealed brood, a period with less capped brood — such as during requeening or a deliberate brood break — interrupts its breeding cycle and is a genuinely useful, low-cost control tool alongside approved miticides used on a set schedule.
This is a general guide, not a substitute for a veterinarian. Always call a vet for diagnosis, dosage and treatment of a sick animal.
Signs to look for
- Newly emerged bees with visibly deformed, shrunken or crumpled wings — a hallmark of heavy varroa-transmitted deformed wing virus.
- Visible reddish-brown mites on the bodies of adult bees, especially between the abdominal segments — check by close inspection or a sugar-shake/alcohol-wash sample.
- A gradual, unexplained weakening of the colony: fewer bees than expected for the season, a spotty or patchy brood pattern, and slower buildup.
- Bees crawling near the hive entrance unable to fly, and in heavy infestations, colony collapse over weeks to a couple of months.
- Higher mite counts typically show up when uncapping drone brood, since varroa preferentially breeds in drone cells.
Checking mite levels
- Do a sugar-shake or alcohol-wash mite count on a sample of a few hundred bees every few weeks during the active season — this gives an actual number to act on rather than a guess.
- Inspect uncapped drone brood periodically, since mites concentrate there before spreading to worker brood.
- Watch for deformed-wing bees at the hive entrance as an early, visible warning sign between formal counts.
- Check more frequently heading into a dearth period or before winter, when mite pressure has the most impact on colony survival.
Treatment
- Use an approved miticide (strip, vapour or other registered treatment) on the schedule recommended for it — under- or over-treating both reduce effectiveness and risk resistance building up in the mite population.
- Time a brood break — during planned requeening, or by deliberately caging the queen for a period — to coincide with a miticide treatment; less capped brood means fewer mites have anywhere to hide from the treatment.
- Rotate between different classes of miticide across seasons rather than using the same one continuously, to slow the mites developing resistance.
- Treat promptly once counts cross a concerning threshold rather than waiting for visible colony weakness — by the time deformed-wing bees are obvious, the infestation is already well established.
Reducing reinfestation risk
- Space hives out where practical — crowded apiaries let mites drift between colonies on foraging or robbing bees more easily.
- Requeen periodically with stock bred for some hygienic or grooming behaviour where available, which helps colonies remove mite-infested brood themselves.
- Avoid combining a heavily infested colony with a healthy one without treating first — combining just moves the problem, and the mite load, into the surviving colony.
- Keep a consistent monitoring and treatment calendar across the whole apiary, since an untreated neighbouring colony can reinfest a treated one.
Animals affected
Open an enterprise page for its full feeding, breed and vaccination-calendar guide.
Frequently asked questions
Can I just let a strong colony fight off varroa on its own?
A strong colony can tolerate a low mite level for a while, but varroa reproduces inside the brood faster than most colonies can outgrow it, and the viruses it spreads do real damage even at moderate mite counts. Regular monitoring and treatment on a schedule, rather than waiting for visible weakness, is what actually keeps colonies alive season after season.
Is honey from a treated hive safe to eat?
Yes, when an approved miticide is used exactly as directed, including any specified timing relative to honey supers being on the hive. Follow the product label’s instructions on when to apply and remove strips or treatments relative to honey flow, and do not use unapproved chemicals as a shortcut.
Why do I see more deformed wings after a dearth period or in autumn?
Mite numbers build up across the season on the back of brood-rearing, so by late season or a nectar dearth, mite loads — and the deformed wing virus they carry — are often at their highest relative to a shrinking bee population, making the damage most visible exactly when the colony can least afford it. This is why a pre-winter or pre-dearth mite check and treatment matters so much.
Does a brood break alone get rid of varroa without any miticide?
A brood break reduces the mite population significantly by removing their breeding sites for a period, but it rarely eliminates an infestation on its own, especially if mite numbers were already high beforehand. It works best as a way to make a miticide treatment more effective — fewer mites are hiding in capped brood when you treat — not as a standalone replacement for treatment.
Signs, prevention and treatment follow ICAR, DAHD and state veterinary-university practice; vaccine schedules are the commonly notified ones and may vary by region or outbreak status. Always confirm with a veterinarian before treating an animal. editorial policy.