Tropilaelaps Mites

There are currently four species of Tropilaelaps mites. Of these only two (Tropilaelaps clareae and Tropilaelaps mercedesae) are considered serious mite threats to the Western honey bee Apis mellifera(Anderson and Morgan, 2007). T. clareae and is already an economically important pest throughout Asia with the newly characterised T. mercedesae was widely spread, and was found on Apis mellifera in regions well outside its native range. In coming years both could spread into temperate regions. Both are considered emerging threats to world apiculture. The potential effects of climate change and the risks this represents for establishment of these pests in the UK are being studied at the National Bee Unit. Tropilaelaps spp. are statutorily notifiable under EU legislation.

Healthy tracheal system in honeybee. Courtesy The Animal and Plant Health Agency (APHA), Crown Copyright

Diseased tracheal system in honeybee. Courtesy The Animal and Plant Health Agency (APHA), Crown Copyright

Geographical Range

The known geographic range of Tropilalaelaps has spread significantly over the last 40 years. The main factor currently limiting survival and spread of exotic mites in the UK is their dependency on a continuous, year-round food supply of immature bees within infected colonies. Under existing climatic conditions, cold winters prevent A. mellifera from producing brood, so any introduced Tropilaelaps will starve. However, even slightly milder UK winters, as anticipated with global warming will support uninterrupted brood production. It is already known that in many parts of the UK there is brood present all year round, including in more northern areas of the country. This direct relationship between climate/host/parasite makes the Tropilaelaps/honey bee model particularly relevant to climate change scenarios.

Life cycle

Acarine eggs in tracheal tube. Courtesy The Animal and Plant Health Agency (APHA), Crown Copyright

The females of T. clareae are light-reddish brown and about 1.0 mm long x 0.6 mm wide, and the males are almost as large as the females (about one-third the size of a Varroa mite). The life cycle and parasitism of A. mellifera is similar to that of Varroa destructor. T. clareae readily infests colonies of A. mellifera in Asia, particularly where colonies produce brood continuously. Adult female mites enter cells containing larvae where reproduction takes place within sealed brood cells. The mother mite lays three to four eggs on mature bee larvae 48 hours after cell capping. Development requires approximately 6 days, and the adults (including the mother mite) emerge with the hatching adult bee then search for new hosts. Mites move rapidly across the brood combs and are therefore easier to spot than Varroa, although they are much smaller. T. clareae has a shorter reproductive cycle than V. destructor, so when both mites are present in the same colony, T. clareaepopulations build up more rapidly. Unlike Varroa, Tropilaelaps only parasitise brood.

Current Status

Currently Tropilaelaps spp have not been found in the UK or the rest of Europe.The National Bee Unit Inspectorate carries out surveillance for these pests each year in apiaries considered “At risk”, for example around ports or freight depots. Beekeepers are strongly encouraged to regularly monitor their hives for their presence, and diagnoses are carried out by the NBU laboratory staff. Any suspect mites should be immediately sent to the Laboratory for investigation.

Further reading

Detailed information about Tropilaelaps mites can also be found in our advisory leaflet ‘Tropilaelaps. Parasitic mites of honey bees‘;
Tropilaelaps spp. can be found on theContingency Planpages of BeeBase;
For more information on this pest please see theOIE Chapteron Tropilaelaps mites;
Please follow the link to download our proposed action in the event of an introduction of Tropilaelaps into England or Wales:Tropilaelaps Risk Analysis.

Adapted from BeeBase, National Bee Unit, Animal Health and Plant Agency (APHA) under the terms of the Open Government Licence (OGL). Crown Copyright.