Getting the buzz on the value of bees
Key text
This topic is sponsored by the Department of Agriculture, Fisheries and Forestry.
Australian agriculture has been getting a free ride from honeybees for nearly 200 years. Their pollination services are worth several billion dollars a year, but Australia's honeybees are under increasing threat, including from a mite known as Varroa destructor.
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(Credit: Paul Zborowski, Close Up Photo Library.)
In many parts of the world the honeybee has been losing its buzz. Unusually high bee mortality has been reported in most of Western Europe. In the United States, the number of honey-producing colonies has declined from about 5.5 million in 1950 to 2.5 million in 2007, and there have been sudden colony losses in Japan, China and elsewhere.
Australia’s honeybees have so far been spared. But scientists and beekeepers are worried that some of the destructive agents suspected of causing the world’s big bee bust have already arrived on Australia’s shores and will soon devastate the bee industry here.
The importance of bees
Worldwide there are more than 20,000 bee species, not all of which have been described by science. But of these there are only seven known species of honeybees – bees that produce and store honey and build long-lasting nests (hives) made of wax. All honeybees belong to the genus Apis and are known collectively as the Apini tribe.
Whilst Australia does not have any native Apis honeybees it does have over 1,600 species of other native bees (Box 1). This diverse set of flying insects has evolved to exploit, and to work symbiotically with, the continent’s huge diversity of plant species, many of which are prolific producers of pollen and nectar. The bees that produce most of Australia’s honey are European honeybees (Apis mellifera), also known as commercial or western honeybees. These were first brought to Australia in the 1800s to pollinate crops and to supply settlers with honey. Within a few decades those early bees had swarmed across most of the country, making themselves at home both in the wild (where they are known as feral bees) and in artificial hives managed by beekeepers.
Honeybees may be most famous for the honey they serve up, but they do many other useful things as well. For example, they produce beeswax, which is used for the manufacture of candles and furniture polish and in food and skin-care products; propolis – a food product, thought to improve heart health and strengthen the immune system; and royal jelly – which has an anecdotal reputation as a health-food product that is thought to lower cholesterol, reduce inflammation, speed the healing of wounds and act as an antibiotic and anti-ageing agent. (The scientific evidence for some of these qualities is still being evaluated, but honey's antimicrobial properties are well established and it seems that Australian native myrtle tree honey may have some of the best such properties in the world – see Further Reading). Most importantly of all, bees play a major role in one of the most fundamental ecological processes – the pollination of plants.
Pollination is the process by which the male sex cells of a plant (the pollen) is transferred to the female sex organ (the ovule) of the same or another plant, resulting in fertilisation and hence sexual reproduction. It is an essential service – without pollination, life on the planet would be very different and probably much less diverse. The most common form of non-animal pollination is pollination by the wind (anemophily). However 90% of pollination requires animals, and the animal most commonly involved is the honeybee.
It is estimated that about one-third of global food production requires animal pollination and that 80-90% of this role is carried out by honeybees, so this tiny tribe is very valuable indeed. In Australia, two-thirds of all horticultural and agricultural crops need honeybees for optimal pollination. Many fruits, such as apples, raspberries and peaches, are more productive, produce better, more attractive fruit and even store better and for longer when they are serviced by honeybees. Lucerne, which is an important crop for feeding livestock such as cattle, is also much more productive when sufficient numbers of honeybees are available to promote pollination. Almond blossoms rely completely on honeybees for pollination – so, no bees, no almonds. It has been estimated that the value of honeybee-reliant agriculture in Australia is as high as $6 billion per year and rising.
| Avocado, Almonds, Onions, Sunflower | 100 % |
| Cucumber, Mango, Apples, Asparagus, Cherries, Kiwifruit, Rock melons, Pumpkins | 90 % |
| Apricots, Watermelons, other melons, Plums | 70 % |
| Peach, Nectarine Pear Orange, Canola Cotton Grapes, Tomatoes |
60 % 50 % 30 % 20 % 10 % |
This data has been compiled from various sources referenced in Further Reading.
Australia’s honeybees are among the most disease-free in the world and are therefore in considerable international demand for their pollination services, especially in those countries that have suffered from sudden colony losses. For example, the value of Australian exports of honeybees to the United States in 2010, mainly for the Californian almond-flowering season, was about $7.5 million. The export of ‘controlled queen bees’ – to reduce swarming and help maintain hive productivity – is also a valuable exercise.
from a flower.) (Credit: Ryszard Maleszka,
Australian National University.)
The residents in a honeybee hive
A typical honeybee hive contains 60 000 – 80 000 individuals of three different kinds: workers (also called foragers once they begin to leave the hive), drones and a single queen. The queen has a much larger abdomen than other bees and she can sting repeatedly without dying. She very rarely leaves the hive; her primary role is to lay eggs – up to 2000 per day – and she is fed and cared for by the worker bees. One of the rare occasions on which she leaves the hive is early in her life when she embarks on a mating flight in search of male bees (drones). After mating she is able to store and selectively release sperm from her spermatheca (a spherical organ in her abdomen approximately 1mm in diameter) to fertilise her eggs for the rest of her life. Unfertilized eggs ultimately produce male drones and fertilised eggs produce either female workers or queens – an issue that is determined solely by the diet on which the larvae are fed (for more information see Box 2).
Worker bees live up to their name, working as cleaners, nurses, guards, foragers, providers, undertakers, air-traffic controllers and engineers. At various stages of their lives they muck out the hive, feed drones and other workers, groom and feed the queen, collect and store pollen and nectar, produce wax and honey, construct honey-comb (used to raise the young and store honey and pollen), dispose of dead bees, and keep the temperature of the hive at around 32 - 35 degrees C.
Compared with worker bees, male drone bees are slackers. They need to be fed by the workers, do not sting and do very little other than impregnate swarming queens with their sperm mid-flight. When they have done their job, or as winter approaches, drones are expelled from the hive and left to die.
Social network
Bees’ brains are about one million times smaller than those of humans, but they are still capable of very complex behaviour. For example, they communicate with each other using what is known as the ‘waggle dance’. When a worker honeybee returns to the hive from a foraging expedition, she performs a ritualised series of moves designed to communicate to other workers the location and value of the resource she has just visited. To do this, she swings her body from side to side about 14 times per second while vibrating her wings, usually without moving her legs. After waggling forward (the ‘waggle run’) for a given length of time she circles back to restart the sequence. Scientists believe that the length of the waggle run indicates the distance to the resource, the intensity of the waggle signifies the value of the resource, and the alignment of the run shows the direction in which the bees should fly (relative to the sun) to find the resource. Followers of the dance appear to interpret it by touching the dancer with their antennae; once they have gathered sufficient information they buzz off to find the resource. (See Useful Sites for a short film about the waggle dance.)
Describes how insects are helping to influence the development of new robots.
Another way in which honeybees communicate is through the release and sensing of pheromones – secreted chemicals that affect the behaviour of others. For example, worker bee larvae emit pheromones that hinder the formation of ovaries in juvenile workers and stimulate them to produce certain proteins in their saliva that is fed to the larvae. Alarm pheromones (composed of isopentyl acetate and other chemicals) are used to inform guard bees of emerging threats to the hive and places other bees on high alert.
The queen also emits pheromones that inhibit the production of juvenile hormones in young workers, which slows their development into worker bees and also prevents them from developing eggs. These queen pheromones are transferred throughout the hive through body contact and help bees to identify each other and to know that their queen is still in residence. If some worker bees don’t receive enough queen pheromones (e.g. if there are too many bees in the hive, or if the queen has died) they start building queen larvae cells in order to produce a new queen. These queen cells may be destroyed by other worker bees that have come into contact with enough queen pheromone. Whether a new queen cell is built ultimately depends on which group (the builders or destroyers) work fastest. In this way the bees carry out a type of ‘election’ to determine whether a new queen is needed for their hive.
Australian Scientists -
Professor Adrian Horridge
Adrian Horridge describes his early work at ANU with Mandyam Srinivasan that involved investigating how bees measure speed through their visual flow.
The combination of behavioural complexity and relative simple biology interests scientists in a range of fields. For example, bees have been used extensively in vision and navigation experiments, and this knowledge is now being used to develop new flying control systems and in robotics.
In other work, scientists at Macquarie University and the Australian National University used honeybees to investigate the short-term effect of cocaine on the brain by administering low doses of the narcotic to honeybees and observed the effect on the bees’ waggle dance (it made them waggle more vigorously, thereby overstating the value of the resource). Australian National University researchers are also using honeybees to investigate the exciting new world of epigenetics – how diet and lifestyle affect the wellbeing of subsequent generations (Box 2). Research such as this could increase understanding of brain function in humans as well as in bees and lead to a better understanding of the impacts of certain chemicals.
Describes DNA Methylation and other ways in which gene expression can be prevented or controlled.
Hard times ahead?
Despite their many impressive skills and tight social cohesion, European honeybees are under threat. In many parts of the world, entire colonies have been dying, a syndrome known as ‘colony collapse disorder’. The cause or causes of this phenomenon are not fully understood, but there are several possibilities. Honeybees are stalked by a range of mites, viruses and other diseases, and their vulnerability may be increased by over-work, the cumulative effects of pesticides, and even climate change.
Australia’s honeybees are already afflicted by several imported maladies. Two bacterial diseases, American and European foulbrood, are found in honeybee colonies in every Australian state (except Western Australia, which is free of European foulbrood) and have the potential to cause significant numbers of deaths. Losses can be minimised, however, by good hive management and (in the case of European foulbrood) the use of low doses of antibiotics.
The small hive beetle (Aethina tumida) is another major pest. It was first observed in Australia in 2002 and has spread widely in the east, especially in New South Wales and Queensland. A prolific breeder, the small hive beetle can cause colony collapse, but it can also be controlled by good hive management. For example, poison-containing traps can be placed in a hive that allow the beetle to enter (but not escape) while excluding honeybees, which are significantly larger.
While some bee-botherers are already in Australia, strict quarantine regulations and good luck have combined to exclude others. For example, several other species of honeybee, which would compete with the European honeybee for nesting sites and nectar and pollen resources, and could introduce new diseases, have not yet made it to Australian shores. These include the African honeybee (Apis mellifera scutelata), the giant honeybee (Apis dorsata), the Cape honeybee (Apis mellifera capensis) and bumble bees (Bombus species, which are already found in Tasmania).
On the other hand, the Asian honeybee (Apis cerana) has recently arrived in northern Queensland to the dismay of Australian beekeepers, environmentalists and agriculturalists. It is of concern because it is known to rob European honeybee hives to the point of collapse, is more aggressive, frequently swarms and may carry diseases to which Australian honey bees have no resistance. It could also have negative effects in the tropical forests of the region, potentially competing with native bees for the pollination of indigenous plants. Asian honeybees are a natural host to a range of nasties, including the Varroa mite. Although the Asian honeybees detected in northern Queensland are so far free of Varroa mites, their widespread establishment would make it even harder to detect any incoming Asian honeybees that might harbour the mites.
attached. (Credit: United States Department of Agriculture.
Photo by Scott Bauer.)
(Credit: CSIRO Entomology.)
The Varroa menace
Several honeybee pathogens have not yet been found in Australia, including the Tropilaelaps mite (Tropilaelaps mercedesae and T. clareae), which are hosted by giant Asian honeybees, and the tracheal mite (Acarapis woodi), which causes a condition in bees known as acarapisosis or acarine disease. But perhaps the most dangerous of all the honeybee’s enemies is the destructor mite – Varroa destructor – and its cousin, V. jacobsoni.
Both these mites were found originally on the Asian honeybee, but both have also recently taken a liking to the European honeybee. On the Asian honeybee they only trouble drones, so their impact on a hive is relatively limited. But on the European honeybee both species are able to parasitise worker bees as well, greatly increasing the harm they can do to colonies.
Until 2000 it was thought that the Asian honeybee was infested only with V. jacobsoni and two other minor species (V. underwoodi and V. rindereri), but two Australian scientists, Denis Anderson and John Trueman, demonstrated that another species was present on Asian honeybees and named it V. destructor. This is the largest of all the Varroa species and probably jumped host from the Asian to the European honeybee sometime in the 1900s, when the trans-Siberian railway brought the two species of honeybee into contact for the first time in several thousand years. The jump by V. jacobsoni to the European honeybee has so far occured only in Papua New Guinea and was first observed in 2008.
From initial observations it appears that V. jacobsoni in Papua New Guinea can cause the same amount of damage to European honeybees as V. destructor. However, as it has not yet spread as far as V. destructor, its global impact is much less. In contrast, two strains of V. destructor appear to have spread widely: one originated in Japan and has spread to parts of Asian and the Americas; the other arose in Korea and has now spread globally, except to Australia. Genetic evidence suggests that both types developed from single female mothers who were able to survive and thrive on the European honeybee.
The Varroa mite attaches itself to the honeybee and feeds on its ‘blood’ (known as haemolymph); it can also infect the bee with bacteria and viruses, further weakening it and eventually causing its premature death. V. destructor has been responsible for the demise of billions of European honeybees and is almost certainly a contributing factor to colony collapse disorder. Its introduction to Australia would likely cause a dramatic reduction in the country’s feral bee population and have major implications for the honey industry and agriculture. (For more information about Varroa, see Box 4.)
honey bee (Apis cerana). (Credit: Paul Zborowski, Close Up Photo Library.)
The role of sentinels
A number of efforts are being made to ward off the threat to Australian agriculture and the Australian beekeeping industry. The National Sentinel Hive Program, for example, was established in 2000 to help detect incursions into Australia by the Asian honeybee, the Varroa and Tropilaelaps mites, and other potential pests such as the African honeybee. It involves the placement and monitoring of empty hives at strategic locations, especially ‘high-risk’ sea ports where these pests are most likely to make landfall in Australia. This program is complemented by the recently established Bee Force project, which is testing a volunteer-based, early-detection approach at the Port of Melbourne that, if successful, could be expanded nationwide.
protecting our bees
Describes how Melbourne’s ‘Bee Force project’ is helping to keep Australia free of the Varroa mite and other invaders.
Despite such initiatives, most experts agree that it is only a matter of time before the Varroa mite (and other threats) arrives in Australia. Colonies of the Asian honeybee were discovered in 2007 in Cairns, although on this occasion they did not appear to carry Varroa mites. The new arrivals were the same genotype as those from New Guinea and are therefore likely to have originated from there. Work is now under way to contain this outbreak, although it has yet to be determined whether this is possible.
The spread of the Asian honeybee throughout Australia would make it more difficult to detect new incursions that do harbour Varroa – because it will be difficult to visually distinguish between the newly arrived bees and those in the existing Australia-based population. If the newly arrived bees originated New Guinea (a high probability given that other arrivals that have been intercepted at eastern Australian seaports since 1995 originated in that region), they could carry V. jacobsoni, as equally deadly to the European honeybee as V. destructor.
The impact of Varroa
Scientists predict the following outcomes once the destructor mite becomes established in Australia:
- The virtual disappearance of feral honeybees.
- A decrease in the number of hived honeybees, as colonies collapse due to infestation.
- An increase in the cost of beekeeping and therefore the cost of honey.
- The replacement of free pollination – currently performed by feral honeybees – by paid pollination.
- An increase in the cost of managed pollination, increasing the cost of agricultural production and therefore the price of food.
There seems little doubt that the eventual arrival of Varroa in Australia will change life for honeybees forever. It could mean the end of agriculture’s free lunch, as feral bees die off, and a very difficult and costly period for the beekeeping industry. Yet it will not spell the complete end of the European honeybee. In managed hives, it is possible to reduce the impact of Varroa through the use of insecticides and improved management techniques (although these will increase the costs of production and affect the quality of bee products). It may also be possible to increase the role of native bees in certain types of agricultural pollination (Box 1, Box 3) and to breed European honeybees that are tolerant or partially resistant to infestation (Box 4). The key to avoiding disaster is to better understand the bee, its enemies and the ecology of pollination. Inevitably, science will play a crucial role in ensuring that the great pollinator and its native cousins win their battle against destruction.
Boxes
1. Native Bees
2. Epigenetics
3. Ensuring sufficient pollinators
4. Fighting the Varroa mite
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Created July 2011, edited August 2012.