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What is it?
Varroa mites are external parasites of bees. The mites, which are about the size of a pinhead, use specialised mouthparts to attack developing bee larvae or adult bees, resulting in deformed bees, reduced lifespan and ultimately the destruction of the colony or hive. These mites are the most important pest of honeybees around the world. There are two species of Varroa that are a potential threat- Varroa destructor and Varroa jacobsoni. Varroa destructor attacks honey bees Apis cerana and A. mellifera, the bumblebee Bombus pennsylvanicus, the scarab beetle Palpada vinetorum and the flower fly Phanaeus vindex. V. jacobsoni is an external parasite that attacks Asian honeybees.
Where is it found?
Varroa mites were originally a relatively harmless parasite of the Asian honeybee. In recent decades they have adjusted to living on domestic European honeybees and have become established in most beekeeping regions of the world. Varroa is not present in Australia, but experts are predicting that Varroa mites will enter Australia at some time in the future because in recent years, Varroa has established in our near neighbours - New Zealand and Papua New Guinea - and movement by transport or natural spread may occur.
What are its effects?
Varroa mites spread naturally between bee colonies by travelling on the bees. Modern beekeeping practices of moving hives and equipment between apiary sites have the potential to spread mites quickly over long distances.
One or sometimes more female mites enter a brood cell in the bee hive laying about five or six eggs each. Newly hatched (nymph) mites feed on the growing bee larva.
Once mites reach maturity they mate, the males die; the females attach themselves to adult bees and feed by sucking their blood. A heavily infested colony may have mites on a third or more of adult bees or brood.
Attack by varroa mite weakens bees, shortens their lives, or causes death from virus infections that would otherwise cause little harm. In severely attacked colonies bees may have stunted wings, missing legs or other deformities. Unless urgent action is taken, the vitality of bees in the colony declines until all are dead.
Varroa mites can remain undetected for up to two years, by which time it is too late to prevent spread to other hives.
What’s the risk to Australia?
The most obvious threat is to Australia’s bee and honey industries. The Varroa mite would decimate Australia’s feral bee population and cause a rapid increase in demand for pollination services. It is estimated that Varroa mite could cost Australian plant industries between $21.3 million and $50.3 million per year over thirty years (Source: CSIRO Submission no. 33, p. 10, to the House of Representatives Standing Committee Inquiry into the Future Development of the Australian Honeybee Industry). Apart from reduced honey production, apiarists would need to repeatedly treat their hives to ensure their survival.
However, the major part of the cost of Varroa would probably be felt not by the honeybee industry but by other industries with crops that rely on honeybees for pollination, including almonds, avocadoes, cotton, stone fruits, pome fruit, melons and pumpkins.
Varroa mites were discovered in New Zealand in 2000 and have already had a major economic impact, with significant control costs and losses of bees, hives, honey production, crop yields and export revenue.
What is being done about the Varroa mite?
Live bees can’t be imported into Australia without strict quarantine measures. Visitors must declare all bee and honey products for inspection, and some States also have their own quarantine restrictions on the movement of honey and bee products in Australia.
The nationally agreed, co-ordinated approach being taken by the Australian Government, Australian Honey Bee Industry Industry Council, Pollination Australia, Horticulture Australia Ltd, Plant Health Australia, Animal Health Australia, Rural Industries Research Development Corporation and the CSIRO are seeking to ensure that the negative impacts of Varroa mite on Australia’s bee, pollination and agricultural industries will be minimised should an incursion occur. These partners have identified 11 projects that will enhance Australia’s preparedness, response and recovery to key biosecurity threats to honey bees and pollination, particularly Varroa mite.
In addition, the policy approaches being developed particularly for Varroa mite, will provide the basis for national action on other exotic pests and diseases that affect honey bees and pollination.
25 Sep 2009