Varroa: the No. 1 Threat

Varroa is recognised as the most important parasite of bees worldwide. Every significant beekeeping country in the world – except Australia – has varroa. Inevitably it will appear here and major efforts will be needed to try to contain and control it. The beekeepers most likely to detect and identify it first will be recreational beekeepers. (Amateurs are concentrated along the coast near ports of entry, and have the capacity to keep a close watch on their bees.) 

What is varroa?

Varroa mites are external parasites of adult honey bees and brood. They feed and reproduce on larvae and pupae. An adult female varroa mite is oval, flat, red-brown and around 1.1 mm long and 1.5 mm wide. Varroa mites can be seen with the naked eye.

 Female adult varroa destructor on the head of a bee nymph. Photo By Gilles San Martin from Namur, Belgium [CC BY-SA 2.0, via Wikimedia Commons]

Female adult varroa destructor on the head of a bee nymph. Photo By Gilles San Martin from Namur, Belgium [CC BY-SA 2.0, via Wikimedia Commons]

What are the impacts of varroa?

Colonies with a low infestation can present as normal but as the population of mites builds the damage to the health of the bee colony become profound.

Effects on the brood include:

  • Scattered brood
  • Crippled bees that are reduced to crawling around the hive
  • Poor flight performance
  • Reduced ability for field bees to return to the hive
  • Reduced foraging ability
  • Smaller and lighter adult bees
  • Reduced life span

Effects on the colony include:

  • Abnormal brood pattern
  • Sunken cells
  • Capping chewed by bees
  • Larvae slumped in bottom and sides of cells

If the infestation is allowed to continue, ultimately the colony will die.

Overseas, the impact of varroa has been decimate the wild honey bee population. Only hived bees with a varroa treatment cycle can survive. The pollination services that wild bees provide to food producers is lost.

For a beekeeper, treating varroa is both time consuming and expensive. Typically it involves the application of miticides to the colony with the attendant risk of honey and wax contamination.

Recreational beekeepers often claim to be the guardians of the Australian coast, keen to spot the first incursion of a foreign pest or disease. Varroa is the number one threat – so now is the time to learn more. BeeAware has detailed information on this pest.

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