Varroa mite and bees

11 October 2023
The Varroa mite has landed in Australia and is currently devastating our bees.

Honey bee with Varroa mite parasite.

The name comes from Marcus Terentius Varro, a Roman scholar and beekeeper. Varroa mites have spread through most of the honeybee populations in the world.

The Varroa is a tiny parasitic mite, about the size of a sesame seed. That’s huge compared to an adult bee – similar to a human with a parasite, somewhere between a bagel and a frisbee in size. It causes enormous harm, as it feeds on the bee’s fatty tissues.

A bee infested by a Varroa mite has a reduced ability to fly, pollinate crops and carry food back to the hive. If enough bees are infested, the bee hive can die.

But even worse, the mite can carry over a dozen viruses (included Deformed Wing Virus, or DWV). In this case, the damage to the individual bee, and the hive, can be exponentially worse. This current infestation doesn’t seem to involve the DWV – so far.

The first Varroa mites in Australia were found in sentinel hives in Newcastle in June 2022. Since then, they been found south near the Victorian Border, and north around Coffs Harbour.

The Varroa mite is an “obligate” parasite – it needs the bee to reproduce, and can survive for only a few days without the bee host. It lays its eggs in the brood cell. Its eggs have to hatch fairly quickly and develop alongside the young bees. The mite is spread by bees, hives or apiary equipment that have been in contact with infested bees in the previous 10 days.

In the first year after the Varroa mite arrived, the official policy was a combination of containment and eradication. But in September 2023, the official policy changed from “eradication” to “management”.

Under the new policy, registered beekeepers have carry out a Surveillance Event, looking for evidence of the Varroa mite, at least once every 16 weeks.

Bees benefit our human food ecosystem in many ways – such as honey. The recreational bee keeper, with a single hive, might collect honey for family and friends, while commercial bee keepers, with hundreds of hives, produce honey worth about $0.25 billion/year.

But bees can also pollinate flowering crops – a $14 billion industry that dwarfs the honey industry. For example, almond pollination (South West of NSW and North West of Victoria) is huge. Almonds have a very short flowering time - about a month. About 15% of Australia’s 700,000 bee hives get shipped in semi-trailers to Riverina/Sunraysia in August each year. They are then shifted to pollinate canola, and so the cycle goes.

The Varroa mite is here to stay.

Many recreational bee keepers will have to shut down as cost of management becomes too high. Commercial bee keepers will almost certainly survive, but costs will increase.

In 2018-2019, Australian agriculture generated $62 billion – and bees contributed to about one third of that. About 20-40% of Australian agriculture depends  on feral/wild bee pollination – but these they will probably mostly disappear, and farmers will be impacted. New Zealand went through their initial Varroa mite infestation around 2000, so many farmers now have managed hives on their property to pollinate their crops.

Australia is starting with a clean slate to deal with the Varroa mite, and has a chance to develop an integrated National Strategy. Digital technology can only help.

Dr Karl Kruszelnicki
Julius Sumner Miller Fellow