Varroa mite

​​​​​​​​​Varroa mite (Varroa jacobsoni and V. destructor) is considered to be the most serious pest affecting honey bees worldwide. Until recently, Australia was the last major beekeeping country free of this pest. In June 2022, varroa was detected in surveillance hives in Newcastle, New South Wales (NSW). This resulted in an eradication response that lasted 15 months. On 19 September 2023, the National Management Group (NMG) confirmed that the eradication of varroa mite was no longer feasible based on technical grounds. As a result, NSW is now operating under an interim strategy to slow the spread of varroa while a transition to management plan is being developed. ​

Description​

  • ​​​​Varroa mites are external parasites of European honey bees
  • Adult females are tiny (about 1.1 mm long and 1.7 mm wide), reddish-brown and shaped like a scallop shell.
  • Adult males are smaller and yellowish-white in colour. 
  • Both sexes have eight legs.
  • The eggs are 0.5 mm long, milky-coloured and at first, rounded.​
cllose up of European honey bee with varroa mite on back
Above: European honey bee with varroa mite on its back (image: Scott Bauer, USDA Agricultural Research Service)

Detection

Varroa can be detected using three main methods: an alcohol or soapy water wash, a sugar shake, or through drone uncapping. 

For more information about each of these detection methods follow the links below:

Beekeepers are encouraged to inspect their hives regularly for signs of varroa. The Australian Honey Bee Industry Biosecurity Code of Practice requires that beekeepers perform a check for external mites at least twice per year.

Surveillance reporting​ 

​Please use the diary entry function in BeeTAS​ to report your external mite checks, even if you do not find any suspect mites. It is important that you report your hive checks, even if varroa has not been sighted, to help provide further reassurance that the mite has not entered Tasmania.

​For further instructions on creating a diary entry in BeeTAS to report a mite check, refer to the BeeTAS User Guide.

If varroa is suspected...

Varroa mites are a notifiable pest, which means if you suspect you have found signs of varroa mite in your hives, you must report it immediately by calling the Exotic Plant Pest Hotline 1800 084 881

It is important that beekeepers follow these steps when varroa is suspected in an apiary to reduce the risk of spread:

  1. Collect a specimen of the suspect varroa mite and place it in a small jar of methylated spirits. Keep the jar in a cool, safe place away from sunlight. Do not mail or forward any samples until advised to do so by a department apiary officer. Never take live specimens away from the apiary as this may spread varroa.
  2. Reassemble the opened hive to its normal position.
  3. Mark the hive with a waterproof felt pen (or similar) so it can be easily identified later. Mark the lid and all boxes of the hive with the same identification number.
  4. Thoroughly wash hands, gloves (and gauntlets), hive tool, smoker and any other equipment to ensure varroa is not carried from the apiary.
  5. Place protective clothes, gloves, veil, bee brush and hat in plastic bag and leave them at the apiary site until advised by a Biosecurity Tasmania Officer.
  6. Before leaving the apiary, inspect your vehicle to make sure there are no bees trapped inside or on the radiator. Check the tray of the truck, ute or trailer as well. Boxes of combs and other hive material must be left at the apiary to avoid moving bees from the apiary.
  7. Call the Exotic Plant Pest Hotline 1800 084 881 or Biosecurity Tasmania 03 6165 3777.​​

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Impacts of varroa

Tasmania is currently free of varroa. If varroa were to enter and establish in Tasmania, the impacts to commercial beekeepers, recreational beekeepers, home gardeners, and pollination dependent horticultural and agricultural industries would be significant. The establishment of varroa in Tasmania would also have a devastating impact on wild honey bee colonies throughout the state with the potential to reduce wild populations by around 95% as has been observed in other countries. This would practically eliminate the free pollination services provided to horticultural/agricultural industries and home gardeners from wild honey bees. 

To prevent the entry of varroa into Tasmania, restrictions on the import of bees, apiary products and used apiary equipment have been in place since the detection in NSW in June 2022. These import restrictions will be reviewed once the transition to management plan has been finalised. See more information on the General Biosecurity Direction​.​

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​​Life cycle

Varroa mites only produce offspring when the honey bee brood is present in hives.

A ​mated female varroa mite will enter a brood cell (drone cells preferred) containing mature larvae just before the cell is capped by hive bees. The female varroa then moves to the base of the cell and submerges herself in the larval food. When the cell is capped, the submerged varroa begins feeding.

Varroa destructor on bee pupa 

Above: Varroa destructor mite on a bee pupa. Image: Gilles San Martin - Wikimedia Commons

​Individual females lay up to six eggs, starting about 60 to 70 hours after the cell was capped and thereafter at intervals of about 30 hours. The first egg laid is male and the others are female. Eggs are laid on the base and walls of the cell, and sometimes on the developing bee.

Female varroa mites take around 8 to 10 days to develop from an egg to an adult. The long interval between the laying of individual eggs means that mites can be at different stages of development in the one cell. Protonymphs hatch from the eggs about 12 hours after being laid. A larger duetonymph stage occurs before the final adult stage.

The single male varroa mates with its sisters while they are in the brood cell.

When the new adult bee emerges from its cell, the young female mites and mother mite also leave the cell, often on the emerging bee.


​How varroa spreads

The mites are very mobile and readily transfer between adult bees.

Varroa spreads between colonies and apiaries when hive components, infested brood and adult bees are interchanged during normal apiary management practices. Beekeepers can spread varroa by moving hives, used beekeeping equipment and queen bees. 

Foraging and drifting bees and swarms can also spread varroa. Mites can move from a forager bee to a flower, and then hitch a ride on another bee or insect visiting the same flower.​

Varroa is not spread in honey.

Further information

Contact

Senior Biosecurity Officer (Apiary Biosecurity)

Julie Lupia
Biosecurity Operations Branch,
Biosecurity Tasmania,
13 St. Johns Avenue,
New Town, TAS, 7008.
Mobile: 0467 805 968