Tropilaelaps mite (Tropilaelaps spp.), possibly a new menace on the Horizon?

Honeybees across the globe are exposed to a number of pathogens, pests and parasites. A newly emerging parasite that could create sever problems for beekeepers in the region is Tropilaelaps spp. Tropilaelaps is an ectoparasitic mite that feeds on the hemolymph of developing honeybees.

Figure  SEQ Figure \* ARABIC 1. Adult female Tropilaelaps, Credits: Pest and Diseases Image Library, Bugwood.org

Just like Varroa Destructor the origins of this parasitic mite can be found in tropical and subtropical Asia, with the primary host for Tropilaelaps being the Giant Asian honeybee, however Tropilaelaps has been found in Apis cerana and Apis florae. Distribution of this parasitic mite has been expanding over the last 50 years well beyond the Asian subcontinent and have been found as far afield as Kenya and Papua New Guinea.

We have already learned from our experiences with Varroa Destructor how effective and destructive mites can be. But what makes Tropilaelaps such a formidable predator, and how and why does it depend on honeybees to survive?

Figure SEQ Figure \* ARABIC 2. Image shows three adult Tropilaelaps infesting a honeybee larva.

Tropilaelaps are unable to penetrate the exoskeleton of the honeybee, unlike their counterparts varroa destructor. Unfortunately this in no way hampers Tropilaelaps, as the adult mite and nymph feed exclusively on honeybee brood, and must continue to do so, or they will die in two days.

The odds continue to stack up against the Western Honeybee since Tropilaelaps mite transitions from egg to adult in the space of approximately 7 days and has no preference between drone or worker brood. Due to Tropilaelaps mite’s noticeably short reproductive cycle, this mite has the potential to surpass Varroa mite infestations in Apis mellifera colonies infected by both species.

Due to the high reproductive rate of Tropilaelaps and short development time of populations, this parasite is extremely difficult to manage. In severe infestations Tropilaelaps has been known to kill up to 50% of the brood population. Brood patterns will become irregular and neglected, along with perforated cell cappings will become visible. Parasitized honeybees will suffer from several issues: reduced life span, lower body weights, shrunken or deformed wings and legs.

Research was conducted by an international team of researchers at Jiaotong-Liverpool University and Liverpool University, focused on mites as they are one of the major threats to honeybee colonies. Their work revealed that there were specific features in the Tropilaelaps mite genome that had been shaped by their interaction with honeybees, and that current chemical mechanisms to control mites are unlikely to be useful for Tropilaelaps.

Figure : Varroa on the left, compared with Tropilaelaps on the right. Credits: Zachary Huang, www.beetography.com

Tropilaelaps should be considered a potential threat to the Caribbean Honey Industry, because this mite has the potential to thrive in any tropical or subtropical regions that have honeybees. Current beekeeping management strategies for Tropilaelaps replicate treatment for Varroa Destructor which include regular requeening with hygienic queen-lines along with the use of screen bottom boards. Cultural control methods such as creating a “brood break”, by caging the queen for a period of 6 – 9 days have proven to be successful in the treatment of both Tropilaelaps and Varroa mites.

As we have learned from the past the absence of Integrated Pest Management Programs by Beekeepers in the Caribbean allowed Varroa Destructor to enter the region quickly and devastate the sector. It is critical as Caribbean Beekeepers we incorporate and document Integrated Pest Management (IPM) into our yearly work plan. See the below example of a Varroa Mite Management Plan from Cornell University, Master Beekeeping Part III: Managing Pests and Diseases, College of Agriculture Life and Sciences.

We also need to have free and open communication and report any incidences of mites within our apiaries to protect our country as well as the region from honeybee pest and diseases that will threaten our bees but also our livelihood.

Cornell University – Master Beekeeping Part III: Managing Pests and Diseases, College of Agriculture Life and Sciences.

References
Mortensen A, Burleson S, Chelliah G, Johnson K, Schmehl D, and Ellis D. 2019. Tropilaelaps mite Tropilaelaps spp. Delfinado & Baker (Arachnida: Mesostigmata: Laelapidae). EENY604 IFAS Extension, University of Florida. https://edis.ifas.ufl.edu/pdffiles/IN/IN106100.pdf (Links to an external site.) (Last accessed: 3rd December 2020).

Dong, X, Armstrong, SD, Xia D, Makepeace BL, Darby AC, Kadowaki T (2016): Supporting Data for “Draft genome of the honey bee ectoparasitic mite, Tropilaelaps mercedesae, is shaped by the parasitic life history”. GigaScience Database, http://dx.doi.org/10.5524/100266), and, as a standard, the sequence data is available in the appropriate public repositories: under accession numbers BioProject: PRJNA343868 and PRIDE: PXD004997.