Tropilaelaps: an Exotic Threat to UK Honey Bees

Tropilaelaps: An Exotic Threat to UK Honey Bees Gay Marris*, Mike Brown*, Selwyn Wilkins*, Andrew GS Cuthbertson**, Dominic Eyre*** (*National Bee Unit, Fera, **Entomologist, Crop & Food Security, Fera, ***Plant Health Entomologist, Fera) Forewarned is forearmed: we take a close look at a potential threat to our honey bees TROPILAELAPS MITES are parasites of honey bee brood. Four species have been documented (T. clareae, T. koenigerum, T. thaii and T. mercedesae), all of which use the giant Asian honey bee, Apis dorsata, Tropilaelaps as their natural host. However, it is mite on A. dorsata pupa now known that two of these, T. clareae and T. mercedesae, also utilise the Western honey bee, Apis t i n U mellifera. e e B l a n o The effects of infestation i t g a n N i r e Parasitisation causes abnormal brood a h W T e y r i b development and death of both brood a s l o C t o and bees, leading to colonies d h n P declining, absconding or even a Apis dorsata, the natural host of Tropilaelaps species collapsing altogether. In severe infestations up to 50% of brood dies and there is a noticeable smell of Western honey bees appear to be Geographical range comparatively more susceptible to the decaying remains in affected hives. The natural geographical range of effects of parasitism by Tropilaelaps Adult bees damaged during than A. dorsata because they lack the Tropilaelaps is currently largely development have reduced life-spans, behavioural defences of Asian honey confined to tropical/sub-tropical zones, lower body weights, and wing and leg bees which are able to remove heavily where these mites are responsible for deformities. infested workers from their colony. very significant economic losses. However, their geographic range has Adult Tropilaelaps mite Also, unlike A. mellifera, A. dorsata spread dramatically within the past 40 (scale: body length 1 mm) can bite and injure Tropilaelaps mites. years, with a marked northward and Apis dorsata colony in Thailand westward expansion. Species relevant to the UK, because they have been known to parasitise A. mellifera, are currently present in Indonesia, the Philippines, Myanmar, China, India, Laos, Malaysia, Papua New Guinea, Sri Lanka, South Korea, Thailand and Vietnam. At the time of writing, Tropilaelaps mites have not been found in the UK or the rest of Europe, but if they were introduced through imports of bees and became established, they have the potential to cause major economic damage and losses to beekeeping and, as a consequence, to agriculture and the environment through disruption to pollination services. Bee Craft June 2011 Page 15 Could Tropilaelaps survive in nymphal stages before becoming the UK? adults. Yes, although the brood requirements Tropilaelaps’ mouthparts cannot pierce of Tropilaelaps are the limiting factors the relatively tough body walls of adult in its establishment in the UK. In areas bees, so they depend on softer brood of the UK that are warmer, for example for food. All stages of mites feed on in the south and east, where there is the haemolymph (blood) of developing brood in colonies all year round, the bees, depriving hosts of the Deformed nourishment required for growth. A. dorsata pupa from mite will survive, even in very small a colony infested with Tropilaelaps mites areas of brood. As long as bees rear When the adult bee emerges, the next some brood, the mites can survive generation of adult mites (and their Could Tropilaelaps reach the and, as the amount of brood reduces, mother) exit the cell to search for fresh UK? many adults enter single brood cells hosts. Pregnant females will die within two days, so must deposit their eggs Yes. There is a significant risk that but do not breed. quickly in a new cell. Within the hive, Tropilaelaps mites could be introduced Tropilaelaps is unlikely to survive Tropilaelaps move readily from bee to into the UK. The primary pathway where there is a complete interruption bee. through which the mites could be to brood rearing during the winter. This life cycle is similar to that of carried is by movement of honey bees, Tropilaelaps is a notifiable ie, queens and package bees Varroa destructor, but Tropilaelaps (workers), for the purposes of pest in the UK develop faster and intervals between international trade. EU legislation now Tropilaelaps are notifiable pests under successive reproductive cycles are very prohibits (with the exception of New EC legislation, so beekeepers are short. Consequently, when both types Zealand) imports of package bees or obliged to report any suspected of mite are present in the same colonies from Third Countries. presence to the NBU (England and colony, Tropilaelaps populations build up far more rapidly. Import regulations are our main Wales) or the relevant agriculture defence against the introduction of department (Scotland and Northern Distinguishing between Varroa and Tropilaelaps (and other very serious Ireland). Keeping an eye out for exotic Tropilaelaps is straightforward: Varroa bee pests and diseases) from pests, including Tropilaelaps, must be is larger, crab-shaped, wider than it is overseas to the UK and it is absolutely a routine part of colony management long and relatively slow-moving; the essential that all beekeepers abide by in the UK. Tropilaelaps mite’s body is elongate them. If you are going to import In addition to apiary inspections for and adults run rapidly across infested queens or bees, make sure that you statutory bee diseases, the NBU brood combs; they also ‘hide’ in brood do so only from countries permitted provides advice and assistance to cells rather than on adult bees. under current legislation and from beekeepers on a range of bee health Means of spread reputable producers. Do not be topics and good husbandry and it runs Tropilaelaps mites are mobile and can tempted to import bees illegally – the training courses for beekeepers on risks are just not worth it. disease recognition and control, Dorsal (top) and ventral (bottom) If you have any queries or need advice usually in conjunction with local views of Varroa destructor (left) and or further information, contact the beekeeping associations. These Tropilaelaps clareae (right) National Bee Unit (NBU), your local include how to look for and recognise Bee Inspector or take a look at the Tropilaelaps. NBU’s BeeBase website The biology of Tropilaelaps www.nationalbeeunit.com All beekeepers should be aware of the Limiting factors mites’ biology, and how to recognise Tropilaelaps mites cannot feed on them. adult bees because their mouthparts Adult Tropilaelaps mites are light are unable to pierce the body wall reddish-brown and, depending on the membrane. As a result, they are species, between 0.7 and 1.0 mm long completely dependent on the softer and approximately 0.6 mm wide. developmental stages of their host They enter cells containing mature bee species for food. larvae, where reproduction takes place All species of Tropilaelaps have an within sealed brood, particularly that absolute requirement for year-round of drones, 48 hours after cell-capping. presence of brood within infected bee Each female lays three or four eggs, colonies in order to survive and which hatch within 12 hours. Over the spread. next five days, mite larvae go through Page 16 Bee Craft June 2011 Acaricides are medicines that kill mites. These are applied either in the feed, directly on adult bees, as fumigants, contact strips or by evaporation. Many of the same acaricides used for Varroa are also likely to be effective against Tropilaelaps. Although currently there are no products specifically approved for the control of Tropilaelaps in the UK, in the event of the mite being discovered, contingency plans would be implemented and emergency approvals sought from the Defra Veterinary Medicines Directorate (VMD) to use varroacides against Tropilaelaps. Biotechnical Methods use bee husbandry to reduce the mite Migratory beekeeping, for example in heather moors, has the potential to spread population through physical means pests and diseases rapidly over long distances. It is essential to check that your alone. Many of the effective methods bees are healthybefore moving them involve trapping the mites in combs of brood, which are then removed and readily move between bees and within Tropilaelaps: parasitic mites of honey destroyed. the hive. However, to move between bees, which is freely available through colonies they depend upon adult bees the BeeBase website Tropilaelaps is considered relatively for transport through the natural (www.nationalbeeunit.com) or by post straightforward to control using processes of drifting, robbing and from the NBU. husbandry methods that simulate swarming. Mites can spread slowly Sending suspect samples to broodless periods. The inability of over long distances in this way. They Tropilaelaps to feed on adult bees, or are also spread within apiaries the National Bee Unit to survive outside sealed brood for through distribution of infested combs Suspect Tropilaelaps adults or larvae more than a few days, is a weakness and bees through beekeeping should be sent immediately to the in the mites’ life cycle, which can be management. NBU for examination. Use a sealed exploited to control it. container, such as a plastic tube or However, movement of infested In areas where the mite is present, stiff cardboard box. Please provide as colonies of A. mellifera to new areas methods such as queen caging, the many details as possible – your name by the beekeeper is the principal and use of artificial swarms and and address, the apiary name and most rapid means of spread. It is comb-trapping methods, to create location (including, where possible, essential to check that your bees are breaks in the brood, should be the Ordnance Survey map reference).

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