Tropilaelaps is a genus of mite native to Asian honey bees. For many years it remained confined to Asia; but Tropilaelaps mercedesae has adapted to the western honey bee, and from 2024 established populations were reported in the European part of Russia and in Georgia. It is moving westwards.

For the beekeeper the meaning is simple but uncomfortable: the habits built around Varroa do not transfer cleanly to this mite.

How to recognise it

• Shape: Long and narrow, roughly 1 mm by 0.5 mm. Varroa is broader than it is long
• Colour: Light orange-brown. Varroa is darker, reddish brown
• Movement: The most distinctive feature. Tropilaelaps runs quickly across the comb, almost darting. Varroa moves slowly and heavily
• Where it is found: Almost entirely in the brood. On adult bees it is seen rarely and only briefly

That last point matters: we look for Varroa on adults, but Tropilaelaps must be looked for in the brood. A beekeeper who checks adults out of habit may see nothing while the colony is heavily infested.

Differences from Varroa

• It reproduces faster. More offspring per cell and a short development cycle
• It cannot feed on adult bees. Its mouthparts cannot pierce the adult exoskeleton; it survives only a few days without brood
• The phoretic phase is short. It leaves one brood cell and quickly enters another
• It uses drone and worker brood alike. Drone brood removal alone is not a sufficient measure

How protective a broodless period is in a temperate climate is not yet settled. In a study in Georgia, mites carried by a natural swarm survived and reproduced in the new colony, whereas those carried only by returning foragers died within four to six days.

The damage it does

• Adults with deformed wings and shortened lives
• Irregular, patchy brood pattern
• Opened or abandoned brood cells
• Transmission of viruses, above all Deformed Wing Virus
• Colony collapse within months if untreated

Monitoring

Brood uncapping — the most reliable method

Opening part of the sealed worker brood and looking is the principal method. Around a hundred cells is a reasonable start. Because the mites move fast, their scurrying is conspicuous once the comb is opened.

Sugar roll — presence or absence only

With Varroa a sugar roll gives a numerical result. With Tropilaelaps it does not: because the mite is rarely on adults, the test answers only whether it is present. It does not measure the level of infestation.

A beekeeper unaware of this may look at a clean sugar roll and believe the colony is healthy.

Control

• Formic acid is regarded as effective because it penetrates sealed brood
• Oxalic acid works less well, because the mite is in the brood rather than on adults
• Brood interruption is a powerful tool
• Drone brood removal is less effective than against Varroa

Licensed products and recommended protocols differ by region. Check the current official advice before treating.

Reporting obligation

Tropilaelaps is notifiable in many countries. Where it is suspected, report it to the competent authority rather than acting alone; early reporting is the most effective way of limiting spread.

What to do now

• Open brood. Make a habit of uncapping part of the sealed worker brood during inspections
• Watch for a fast-running mite. If something small darts across the comb, it is not Varroa
• Record colony movements. When an invasive pest arrives, these records make tracing possible