Mites are the largest problem group in beekeeping today. The single greatest cause of colony losses is in this group.

Three mites

• Varroa destructor: The commonest and most destructive. Found almost everywhere
• Tropilaelaps: Invasive; of Asian origin, its range is expanding
• Tracheal mite: Lives in the breathing tubes; its economic importance has declined in many regions

What they share: a host shift

The original host of Varroa and Tropilaelaps is the Asian honey bee. That species evolved alongside the mites over millions of years and developed defensive behaviours: grooming, hygienic behaviour, a short brood period.

The western honey bee has no such history. That is why the mites are destructive in this species.

Varroa and Tropilaelaps compared

• Shape: Varroa is broader than long; Tropilaelaps is long and narrow
• Movement: Varroa is slow; Tropilaelaps runs quickly across the comb
• Location: Varroa is found on adults too; Tropilaelaps almost entirely in brood
• Monitoring: A sugar roll gives a numerical result for Varroa but only presence or absence for Tropilaelaps

That last point is critical: a clean sugar roll is not proof that Tropilaelaps is absent.

The real damage: virus transmission

The most destructive effect of the mite is not its feeding but its transmission of viruses. Deformed Wing Virus is injected directly into the bee.

Colony collapse can therefore occur without the mite count being especially high.

The basis of control

• Measure. Regular monitoring by sugar or alcohol wash
• Try the non-chemical option first. Brood interruption, drone brood removal, trap comb
• Use a licensed product if needed. Rotate the active substance
• Measure the result. If the expected drop does not occur, resistance may be involved

Timing

The critical moment of the year is late summer; the winter bees are reared then and the mite feeds on precisely their fat body.

The mite level in August largely determines how many colonies are alive in March.

Reporting

Tropilaelaps is notifiable in many countries. If a suspect mite is seen, preserve the specimen in alcohol and report it to the competent authority.