Bees more deadly than spiders in Australia
ASK HALF A DOZEN Australians to nominate the country’s deadliest creatures and they’ll probably rattle off an impressive catalogue of snakes, spiders and sharks with frightening capabilities to kill humans. The blue-ringed octopus, stonefish and box jellyfish are also likely to get a look in. But who’d expect to see the European honey bee on the list?
And yet this diligent little insect – first brought here in 1822 – kills one or two Australians a year. On average, sharks annually claim fewer lives and the national tally of deaths from spider bites is also lower.
For most of us, a bee sting causes only localised pain and swelling. The insects produce venom, known as apitoxin, in abdominal glands and store it in special sacs. Although the toxin is poisonous to humans, each sting injects no more than 0.1 mg. It’s estimated it would take at least 500 jabs to kill the average adult human and this has never been known to occur in Australia. However, up to 3 per cent of the population is thought to be allergic to honey bee venom. Within minutes of being stung, allergic individuals will develop symptoms of anaphylactic shock, during which airways can be obstructed and blood pressure plummets.
Despite the potential danger, no-one is celebrating the anticipated arrival in Australia of a tiny invader that’s expected to decimate the nation’s European honey bee population. Identified, described and assigned the Latin name of Varroa destructor in 2000 by CSIRO scientist and international mite expert Dr Denis Anderson, the parasite is blamed for many billions of dollars of lost agricultural production worldwide since the 1980s. Although mites are common bee parasites, none is as debilitating to the European honey bee as V. destructor, which Denis and his co-workers believe is a mutation of a Korean mite strain that first appeared during the 1960s and began spreading worldwide two decades later.
It’s now causing havoc for agriculture on every populated continent except Australia and recently became established in Papua New Guinea and New Zealand. “There is no longer a question of if it arrives here but when,” Denis says.
Protecting our native bees
WITH TWO-THIRDS OF Australia’s food crops relying to some extent on pollination by European honey bees, the insect is estimated to be worth a massive $1.7 billion a year to the national economy. Crops that will be hit particularly hard range from melons, stone fruit, apples and pears to lucerne, cotton and canola. Some, such as almonds, are 100 per cent dependent on honey bee pollination, and rely on the deliberate placement of hives near groves. Growers presently pay a $50 fee per hive for the thousands that are strategically placed in South Australia and Victoria each August. Such severe declines in Australia’s managed bee population are predicted due to V. destructor that the cost of this service per hive will quadruple.
But recent studies have also hinted at wider ecological impacts. The European insect’s consumption of nectar from eucalypt flowers, for example, has been implicated in the demise of the nationally endangered swift parrot. Likewise, declines of bird species in the Adelaide Hills have been linked to competition from colonising feral bees for nectar and tree-hollows.
The European honey bee may also have affected the distribution and numbers of local bees, although the introduced species has been here so long its impact on native insects is difficult to prove. The V. destructor crisis may provide an opportunity for our own mite-resistant native species to shine.
“[Native] stingless bees can be excellent pollinators of tropical and subtropical crops such as macadamias, coffee and mangos,” says CSIRO’s Dr Tim Heard, a native bee expert. “With the domestication of stingless bees that is taking place, commercial use of these to pollinate crops may be possible in coming decades.”
Native bees good a hive building
THE JAPANESE HAVE SHOWN keen interest in the hive-building species of native bees because they’re stingless, making them attractive pollinators for high-density glasshouse production. And the nuclei for hives of at least one colonial species are already available from Queensland suppliers for east-coast delivery by post. At the University of Adelaide work is underway to breed blue-banded bees, a solitary species that occurs in most Australian gardens, as pollinators of greenhouse crops such as tomatoes.
So far, 1647 native Australian bee species have been identified and named, but hundreds more are probably yet to be discovered. They’ve never had the chance to enjoy the smorgasbord of crop flowers now available here without competition from European honey bees. Subsequently, no-one’s sure how our native species will respond to the changing conditions. But there’s every chance these native pollinators will turn around and do a terrific job.
Source: Australian Geographic Oct – Dec 2008