Varroa mite

Varroa mite (Varroa destructor) is an external parasite of honey bees that feed and reproduce on larvae and pupae, causing malformation and weakening of honey bees as well as transmitting numerous viruses. Heavy varroa infestations can cause colony death.  

Varroa mite are small, oval-shaped reddish-brown mites that parasitise adult honey bees and the brood. The mites weaken and kill honey bee colonies and can also transmit honey bee viruses.  

Varroa can quickly spread when uninfected bees contact infected bees, hive products, plant material, hives and contaminated beekeeping equipment. 

Varroa mite is the most serious threat to our honey and pollination dependent industries. 

Impact on bees 

Varroa mites weaken bees, reduces their lifespan and increases the spread of viruses. If left untreated, varroa mites will kill a honey bee colony.  

Varroa mites are a vector for a number of honey bee viruses including deformed wing virus, sacbrood virus and acute bee paralysis virus. The combination of Varroa mite and deformed wing virus is a leading cause of colony collapse in other countries.  

Impact on pollination 

Honey bees, managed or feral, are the most effective pollinators of commercial crops due to their physical adaptions, high foraging activity, large colony sizes and specialised pollination techniques.  

The introduction of Varroa mite to North America, Europe and New Zealand caused a decline in numbers of feral honey bee managed colonies. In some areas, 95-100 per cent of feral honey bee hives died within three to four years of infestation.  

Impact on the economy

If varroa mite establishes in Western Australia, it is likely that 50-60% of beekeepers (mostly hobbyist and part-time commercial) will stop beekeeping due to the difficulty of managing the pest, movement restrictions and rising costs. Larger commercial operators are less likely to be impacted, but their hive numbers could still be reduced.  

It will become increasingly difficult for Western Australian honey to maintain its reputation as pure and chemical-free as varroa mite spreads.  

Pollination dependent industries who currently receive free pollination from feral and managed hives will rely more on paid pollination services. The cost of these services will likely increase over time as the cost for beekeepers to manage hives increases and resistance to treatments spread.

Varroa mites are oval-shaped, around 1.1 mm long and 1.5 mm wide (slightly larger than a poppy seed). Mites are easily identifiable to the naked eye and are a reddish-brown colour.  

Under the Australian Honey Bee Industry Biosecurity Code of Practice, all beekeepers are required to check at least one hive per apiary for external parasites, twice per year, i.e. in autumn and spring. Varroa are very difficult to detect during regular brood inspections, therefore beekeepers are required to use one of the following mite surveillance methods:  

• sugar shaking
• alcohol washing
• drone uncapping.

Sugar shaking is non-destructive to bees, while alcohol washing and drone uncapping is fatal to the tested bees. Sugar shake kits can be bought from beekeeping supply stores or made at home.