The federal government has abandoned its attempt to eradicate varroa mite (Varroa destructor), a parasite that attacks honeybees, with the response authorities saying eradication is “no longer feasible“.
The National Management Group driving the varroa mite eradication program in Australia has now entered a management phase, and is developing a new plan.
Varroa mites feed on the fat of honeybee (Apis mellifera) larvae and pupae, stopping them from using it as energy. They also harbour viruses dangerous to bees. Untreated, the mites destroy bee colonies completely.
Australia was one of the last places in the world free of varroa mites. While the mites don’t infect native bees, they can carry viruses that could damage native bee populations.
Mites were found in Townsville in 2016 and 2019, and were successfully eradicated by 2020. This latest outbreak began in Newcastle in June last year. About 14,000 hives have been destroyed in the eradication efforts.
“It was always understood that the eradication strategy had a significant risk of failure,” says Professor Saul Cunningham, director of the Fenner School of Environment and Society at the Australian National University, who was not involved in the management group.
“Varroa mite will cause significant economic damage in agriculture, and so it is vital that we focus on adaptation to life with Varroa. We can learn from overseas, where people have lived for decades with this honey bee disease, but Australia needs to adapt its own solutions because of our unique biodiversity, climate and agriculture.”
Dr Emily Remnant, a honeybee geneticist at the University of Sydney’s School of Life and Environmental Sciences, predicts an “initial period of volatility as Varroa establishes”.
“Over the next few years we will experience significant colony losses in our managed and feral bee populations as the industry transitions to management,” says Remnant.
“On a positive note, currently Australia remains free from deformed wing virus, a damaging disease spread by mites, so colony losses may not be as severe initially.
“Ultimately, it is the viruses that are spread by mites that cause the biggest colony losses, so we must continually monitor virus presence in Australian bees during the Varroa establishment period to ensure that we remain free of viral diseases.”
Remnant calls for a “coordinated, sustainable national strategy” to manage the parasite.
“Our approach must avoid over-reliance on synthetic chemicals, which rapidly leads to resistance in Varroa populations and contributes to poor bee health.”
Dr Mary Whitehouse, a senior research scientist at Macquarie University, agrees.
“Using miticides to contain the mites is a good response, but varroa is very effective at developing resistance to miticides. We will need a multi-pronged approach, which includes miticides, but also a number of other methods,” says Whitehouse.
“We are working with the bee-keeping industry and researchers from New Zealand and the United States to identify a range of non-chemical varroa mite control methods that could be effective in Australia. But when and how these control methods are used will affect their ability to control the mites.”
It’s believed that Varroa destructor gained a foothold in the feral or wild bee population, which means that eradication of the parasite would have been very difficult.
Dr Kit Prendergast, a native bee ecologist at Curtin University, says the impending Varroa should be taken as a signal to focus on native bee populations.
“One of the big issues here is feral honeybees. These populations have been harming native wildlife for decades, and it is only now that people are beginning to realise the risks feral honeybees pose, albeit for pest control by being a reservoir of diseases to managed honeybees,” says Prendergast.
“What frustrates me most as a scientist and bee conservation biologist is the lack of monitoring. Due to the heavy investment into honeybees, we don’t know the status of most native bee populations and their flower hosts – how viable is it to propose native bees can compensate for honeybee declines for pollination of various crops? How are native bee populations doing in areas where honeybee populations have declined? How are they affected by chemical control measures targeted at honeybees?
“Our indigenous bees have been neglected for far too long, and it’s time we started protecting them – including from feral colonies of honeybees.”