Varroa mite, bee mite
Varroa jacobsoni. Note, in 2000, research found that the population of Varroa jacobsoni was made up of two species, Varroa jacobsoni and Verroa destructor. The latter is the damaging species of European honeybees (see Fact Sheet no. 327).
Widespread. Asia [including Indonesia (Irian Jaya)], the Philippines, and Malaysia], Africa, North, South and Central America, the Caribbean, Europe, Oceania. It is recorded from Australia (localised and under active eradication), New Zealand, Papua New Guinea and Solomon Islands.
Asian honeybee (Apis cerana). The Asian honeybee has evolved with the mite, Varroa jacobsoni. The mite does not normally reproduce on the European honeybee (Apis mellifera) but, in 2008, a survey in Papua New Guinea found Varroa jacobsoni on male ('drone') and worker 'brood' (developing larvae and pupae).
This new strain of Varroa jacobsoni is widespread in Papua New Guinea, but it has not been found in Solomon Islands or Irian Jaya. In those two places, Varroa jacobsoni reproduces on Asian honeybees. However, in both places a very small number of mites were found that reproduce only on European honeybee male larvae.
The adult female mite is reddish-brown to dark brown, flattened, oval (like a crab), 1.0-1.8 mm long, 1.5-2 mm wide (Photo 1). Adult males are yellowish, with lightly tanned legs and spherical bodies, 0.75-0.98 mm long, 0.7-0.88 mm wide. On adult Asian honeybees, they are seen on the thorax or within abdominal folds (Photos 2&3).
One or two mated female mite enters a honeybee brood cell (where larvae and pupae develop) before it is closed, and each one lays 5-6 eggs; the nymphs hatch and feed on the bee larvae (Photo 4). The nymphs mature, mate, and the males die; the females attach themselves to the adult bees and feed on their blood (called 'haemolymph' in an insect).
Varroa jacobsoni only reproduces on male (drone) honeybee larvae as the bees can detect and remove them from worker bee larvae and worker brood cells. The mites are obligate parasites of honeybees and do not survive long away from the host.
Spread occurs easily within the hive as the mites are mobile. After hatching, they attach to an adult or infect other larvae and pupae. There are other ways, too: when bees rob the nectar from infected hives, when they enter by mistake, or when beekeepers place infested combs in non-infested hives. Long distance spread may also occur during normal habits of honey bees, i.e., swarming, robbing (taking nectar from other hives) and drifting (entering another hive by mistake).
The mites live for about 2-3 months. When the colony is not breeding and brood is absent, the mites survive fastened to adults, feeding on their haemolymph.
The Asian honeybee and the mite have evolved together, and because of this the bee has adapted to withstand varroa mite infestations. To reduce the impact of the mite, the workers remove them from the brood and brood cells. They do not normally reproduce on European honeybees, but exceptions have been found. The impact of these new strains is not yet known, but is likely to be considerable, leading to reduced honey production and pollination of food crops.
There are accepted ways of monitoring for mites, and three methods are provided. Early detection and reporting is important as it improves the chances of containing and eradicating introductions, therefore, monitoring should be done quarterly at least:
Method 1 (Uncapping drone cells)
Method 2 (Sugar shaking)
Method 3 (Sticky screens)
The two species, Varroa jacobsoni and the more damaging Varroa destructor can be separated by DNA analysis.
Multiple genetically different populations of Varroa. jacobsoni exist. In Papua New Guinea, a strain has been found that has switched hosts and reproduces on European honeybees. There are other strains (in Solomon Islands and Irian Jaya) that partially reproduce at low levels on male European honeybees. Preventing the further spread of Varroa jacobsoni, and its strains, between countries is of the utmost importance. Countries may wish to enact legislation and devise codes of conduct to minimise the risk of introduction of exotic bee pests and diseases as well as managing those that are endemic. Such a code, developed in 2016 for Australia is provided as an example: http://beeaware.org.au/wp-content/uploads/2017/05/Australian-Honey-Bee-Industry-Biosecurity-Code-of-Practice.pdf, and the Biosecurity manual for beekeepers: http://www.planthealthaustralia.com.au/wp-content/uploads/2016/02/Biosecurity-Manual-for-Beekeepers.pdf.
There are a number of control measures aimed at commercial beekeepers as well as the general public. Some of these may form part of national biosecurity legislation to contain the entry of varroa mites and the spread of endemic pests. Notes, are also provided on physical and sanitation controls and those involving chemicals in case they are needed against strains of Varroa jacobsoni that infest European honeybees.
Surveys and sampling (for purposes of biosecurity):
Public awareness to control mites:
Physical methods to control mites:
Sanitation to control mites:
There are times when it is necessary to sterilise hives and equipment. This might be when there has been a mite infestation, the hives and equipment are second-hand or before storage. EITHER:
Treatment of mites on the bees (see Fact Sheet no. 327):
AUTHOR Grahame Jackson
Information from BeeAware. Plant Health Australia. (http://beeaware.org.au/archive-pest/varroa-mites/#ad-image-0); from Biosecurity manual for beekeepers. (http://www.planthealthaustralia.com.au/wp-content/uploads/2016/02/Biosecurity-Manual-for-Beekeepers.pdf); Varroa mite detection in Townsville. Department of Agriculture and Fisheries. Queensland Government. (https://www.daf.qld.gov.au/animal-industries/bees/diseases-and-pests/asian-honey-bees/general-information-on-varroa-mites). Photo 1 Lilia De Guzman, Bugwood.org. Photos 2-4 Walker K (2005) Varroa Mite (Varroa jacobsoni). PaDIL - (http://www.padil.gov.au).
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
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