Invasive Species Council

Hot Issues
- bumblebees reach mainland Australia
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Bumblebees are in the limelight following the recent capture of individuals in Brisbane and Melbourne and yet another proposal by tomato growers to introduce them as pollinators.

The following articles, reprinted from Feral Herald 1:4, July 2003, examine the worrying trends...
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on this page...

Bumblebees Buzzing

Why not Bumblebees?

Parrots & Bees

Bumblebees in Horticulture

Native Bees or Bumblebees for Crop Pollination?

Review of the Horticulture Australia Tasmanian impact assessment.

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Bumblebees Buzzing
by Anne Dollin

On 8th May 2003 a bumblebee (Bombus terrestris) was found by chance on Fisherman's Island, the major port in Brisbane. It was a worker, caught foraging on flowers. Worker bees are unlikely to survive a sea voyage. So this discovery unfortunately suggests that a queen bee arrived some time ago and has already built a nest and bred some workers on the island.

A single bumblebee nest may produce hundreds of new queens which may disperse up to 30 km, and in Brisbane's warm climate queens may be produced throughout the year. Even if Brisbane's summer temperatures adversely affect the population, the chances are high that bumblebees could spread from Fisherman's Island into the parks and gardens of Brisbane.

The crucial task of eradicating colonies has been given to the Queensland Department of Primary Industries. The DPI's official Bombus terrestris Pest Survey Procedure calls for inspection of 'all areas where foraging is likely to occur within a 2 km radius of the interception site', and of mainland areas adjoining Fisherman's Island. Worker bumblebees regularly forage 500 to 1750m from their nest. So it is vital that this proposed surveillance is carried out. The DPI is issuing a public alert, asking that sightings be reported to the DPI call Centre on 13 25 23.

and in Melbourne...
On 20th May 2003 a bumblebee (B. terrestris) was caught on the Appleton Dock wharf in Melbourne. In this case the bee was a queen and it was found on the back of a wharfie unloading a ship from New Zealand. A thorough search by AQIS failed to find any other bees in the cargo.

Victoria is already taking precautions against bumblebees because the introduction of B. terrestris is listed as a potentially threatening process under the Victorian Flora and Fauna Guarantee Act. The Victorian Department of Primary Industries has produced a useful Agnote entitled Keep Victoria Bumblebee Free, giving descriptions and photographs of the bees (available from the DPI Web Site). Several thousand copies are being distributed in the area surrounding Appleton Dock and a further 10,000 copies have been sent to Tasmania for distribution to airports, seaports and government service centres. The public is asked to report any sightings to the Customer Service Centre on 136 186.

A further 8.5 hours of survey work around Appleton Dock failed to find any further bumblebees. So, hopefully this bumblebee that was found had not yet established a nest. However, the discoveries of bumblebees both in Melbourne and in Brisbane within one month highlights the level of vigilance which will be required to keep the Australian mainland bumblebee free!

Anne Dollin manages the Australian Native Bee Research Centre and the Aussie Bee web site.

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Parrots & Bees
Andrew Hingston & Stephen Mallick

The swift parrot (Lathamus discolor) is listed as nationally endangered, because fewer than 2500 adults remain in the wild. The processes traditionally considered as the principal threats to the swift parrot are destruction of foraging and nesting habitat, and collisions with human-made structures. Because swift parrots are dependent largely on the nectar and pollen of Eucalyptus globulus and E. ovata for food while breeding, we considered the possibility that introduced social bees that also consume these resources can also be regarded as threats to the swift parrot. We found that honeybees (Apis mellifera) and bumblebees (Bombus terrestris) usually consumed most nectar from these flowers, and that flowers were virtually devoid of nectar when these bees were active.

Thus, introduced social bees have the same net effect as the destruction of foraging habitat, and must also be considered as threats to the swift parrot. Because honeybees do not forage in large numbers at temperatures below 15¡C, early mornings and cold days have provided a window of opportunity for swift parrots in the absence of competing honeybees. However, the recent introduction of the bumblebee appears to be closing this window because it is able to forage at much lower temperatures than honeybees.

This is the abstract from:
Hingston, A. B. and Mallick, S. A. (2003), Are introduced social bees a threat to the endangered swift parrot? In: Proceedings of the Birds Australia Members' Day and Annual General Meeting. Birds Australia, Geography Department, University of Tasmania.

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Bumblebees in Horticulture
by Tim Low

Apart from the problem of bumblebee stowaways, there are the plans by horticulturists to import bumblebees to mainland Australia to pollinate greenhouse tomatoes. Environment Australia keeps rejecting their proposals on environmental grounds, but the applications keep coming.

In 2002, Horticulture Australia funded a massive study (costing $239,266) to assess the impact of bumblebees in Tasmania. Although this study found that bumblebees dramatically increased seed output in two weed species, horticultural associations are putting a positive spin on the findings.

In the next two articles, Anne Dollin looks at the potential of native bees as greenhouse crop pollinators, and Andrew Hingston critiques the Horticulture Australia study.

At a conference later this month the Australian Hydroponics and Greenhouse Association will decide whether to submit an application to import bumblebees. We hope they will pursue the promising option of native bees instead.

Quotes from the Bumblebee Study funded by Horticulture Australia:
"Given a low number of establishing queens and, therefore, low genetic diversity, bumblebees in Tasmania have been extremely invasive." (page 29)

"Many quirky changes to seed set of various plants were recorded by the public, e.g. an increase in the seed set of orange nasturtiums over yellow nasturtiums, cross-pollination of snapdragons by bumblebees producing a new colour variety, efficient pollination of rhododendrons by bumblebees resulting in early flower droop, and an increase in seed set of some beans crops and blueberries, but a dramatic reduction in yield of one broad bean crop due to nectar robbing." (page 3)

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Native Bees or Bumblebees for Crop Pollination?
by Anne Dollin

Australian horticulturalists are campaigning to import European bumblebees to mainland Australia for greenhouse crop pollination. Bumblebees are often used overseas to pollinate greenhouse crops such as tomatoes, greatly improving productivity. However, Australia has no native species of bumblebee and applications to import bumblebees so far have been rejected by AQIS on environmental grounds.

To grow large, round tomatoes, the flowers must be well pollinated. Outdoor crops are pollinated by wind currents but inside a greenhouse the flower trusses must be individually vibrated. In Australia this is currently done with an electric wand - a costly and labour intensive process. So growers are keen to acquire exotic bumblebees which can do this for them.

Practical Hydroponics and Greenhouses magazine (Issue 69) suggested that there is a good chance that bumblebees will be illegally imported by impatient tomato growers. Such attempts, however, may be doomed to failure. The feral bumblebees in Tasmania are all descended from a single fertilised queen. They are so inbred that breeding of these stocks may not be commercially viable. The Tasmanian bees also carry an extremely high infestation of the pollen mite, Kuzinia laevis, which would adversely affect commercial breeding. So bringing a couple of Tasmanian bumblebees to the mainland will not solve the tomato grower's dilemma.

Melissa Bell of the University of Western Sydney Ð Hawkesbury, in collaboration with the Australian Native Bee Research Centre, is researching the potential of native blue banded bees (Amegilla) for greenhouse tomato pollination. The research is still in progress but already Melissa has shown that these bees adapt well to the confined conditions of the greenhouse and will nest in compact mud bricks. Furthermore in a recent tomato pollination trial, blue banded bees were as effective as the electric wand in increasing fruit weight and improving fruit roundness.

Other native bee species have also shown potential for the pollination of greenhouse crops. Pablo Occhiuzzi of the University of Western Sydney - Hawkesbury found that Australian stingless bees (Trigona) thrived in greenhouse conditions and improved fruit weight and yield in a capsicum crop. Katja Hogendoorn of Flinders University found that green carpenter bees (Xylocopa) effectively pollinated a tomato crop in a flight cage.

Further research is urgently needed to allow commercial development of these species. Nevertheless the use of Australian native bees by the greenhouse crop industry could save our vulnerable environment from the impact of yet another exotic invader.

For further information about research into Australian native bees, visit the Aussie Bee web site

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Potential ecological impacts of the Eurasian bumblebee Bombus terrestris in Australia: assessing the assessment.
by Andrew B. Hingston
School of Geography & Environmental Studies, University of Tasmania,
GPO Box 252-78, Hobart 7001, Tasmania.

This is a shortened version of:
full paper (36 Kb Word 5 document)

Since 1988 the Eurasian bumblebee (Bombus terrestris) has been used in many countries to pollinate greenhouse crops, particularly tomatoes. Within four years of the development of the international bumblebee breeding industry, feral bumblebees were discovered in Tasmania. How they entered is not known, but their importation was not sanctioned by government.

After their establishment in 1992, the Tasmanian Greenhouse Tomato and Vegetable Growers Association applied in 1995 for permission to import more bumblebees to widen the genetic base. In 1997 Gosford Integrated Pest Management Services applied to import bumblebees to the mainland, and in 1999 the Australian Hydroponics and Greenhouse Association (AHGA) also applied to import bumblebees. Although these applications were rejected because of ecological concerns, some horticulturists continue to lobby for bumblebees (e.g. Goodwin & Steiner 1999; Cooke 2001; Carruthers 2003). However, the AHGA has vowed to reapply only if further research shows that bumblebees are ecologically benign.

To obtain a clearer picture of the impact of bumblebees in Tasmania, Horticulture Australia Ltd (HAL) agreed to provide $239,266 for a three-year environmental impact study (EIS) conducted by the Tasmanian Museum and Art Gallery (Hergstrom et al. 2002). That EIS was published late last year, and has been embraced by the vice-president of the AHGA as evidence that bumblebees have little impact (Carruthers 2003). Carruthers wrote a recent article in the magazine he edits and concluded that 'the environmental impact study into bumblebees in Tasmania is evidence that bumblebees will not dramatically change the current status of native and agricultural ecosystems'. In the editorial he stated that there were 'no compelling reasons why bumblebees should not be allowed import into mainland Australia'. However, his view is not supported by the EIS, nor by papers published in scientific journals.

Rate of spread
Carruthers stated that 'It seems that bumblebee populations are spreading in Tasmania at the rate of 10km annually' and 'in the decade since its introduction into Tasmania, the bumblebee is far from ubiquitous'. However, both the EIS produced by the Tasmanian Museum and a study by other researchers showed that bumblebees had spread at around 25 km annually and were established across most of Tasmania within 10 years of their introduction (Hergstrom et al. 2002; Hingston et al. 2002).

Invasion of native vegetation
Carruthers also concluded that bumblebees were 'generally found in urban areas' in Tasmania. Similarly, the EIS concluded 'In Tasmania, constant flower abundance occurs mainly in urban and rural areas, and this was where bumblebees (and their impact) are concentrated'. However, the EIS data do not prove this contention.

Their conclusion was based on the finding that only 11% of bumblebee observations reported by the public that involved more than one bee were in native vegetation, while 46% were in urban areas and 39% in rural areas. However, their survey reflects only the frequency with which people encounter bumblebees, which depends upon the densities of humans as well as bumblebees. People may see bumblebees more often in urban and rural areas because there are more people in these areas.

Also, the EIS did not interpret the many observations of only one bee as evidence of colony establishment). While this is justified if an area was searched thoroughly, the questionnaire merely asked 'In one minute, how many bumblebees did you see in the area'. Obviously, seeing one bumblebee in one minute does not rule out the presence of a colony. A study published in Austral Ecology found evidence of bumblebees breeding in native vegetation in wet and dry zones across an area of approximately 30,000 km² in Tasmania. This included six national parks, including four of the five in the World Heritage Area, and the most remote parts of Tasmania, up to 40 km from gardens, 61 km from small towns and 93 km from large towns. Evidence of breeding was found in all of Tasmania's major native vegetation types, from sea level up to 1180 metres (Hingston et al. 2002).

Impacts on native flora and fauna
Carruthers alleged that bumblebees exhibited 'a distinct preference for introduced, rather than native plant species'. This claim was also made in the EIS, on the basis of observations made by the general public and by observers walking through a variety of vegetation types. Because of this, Carruthers concluded that bumblebees have 'little impact on native plant species'. However, the EIS did not prove this contention because both studies may have been confounded by differing abundances of introduced and native flowers in the areas surveyed, which were not recorded. Irrespective of whether bumblebees show a preference for foreign plants, they are clearly capable of impacting on a wide range of Australian plants because they have been recorded foraging on many of these in Tasmania. Bumblebees were recorded visiting the flowers of 60 species and 19 families of native Tasmanian plants near Hobart in 1996-97, often in large numbers (Hingston & McQuillan 1998a). This list continues to grow and now encompasses 139 species and 32 families (species observed by the general public being visited only once by bumblebees in the HAL-funded EIS not included).

Impacts on weeds
Bumblebees forage heavily on flowers of many introduced plants, raising the possibility that they will enhance seed production in some existing weeds and cause other previously benign plants that were poorly pollinated (sleeper weeds) to become weeds. Of this extensive list of beneficiaries of bumblebee pollination, the EIS investigated only three existing weeds and no sleeper weeds.

Of the three weeds, a dramatic increase in seed set was found in two species in the presence of bumblebees. To quote from the EIS: 'A significant increase was found in the seed set of two weed species with pea-type flowers: Greater Trefoil, Lotus uliginosis (40.2%) , and Tree Lupin, Lupinus arboreus (29.7%).' A decrease in seed set was found in a third weed, Scotch thistle (Onopordum acanthium). However, the research methodology employed was flawed, leading to potential underestimates of the role of bumblebees in increasing seed set. When comparing seed set in areas with and without bumblebees, the researchers did not take account of other variables such as flower numbers, abundances of other pollinators, levels of seed predation, environmental conditions, and the spatial arrangement of flowers. Also, the decision about whether or not bumblebees were present was based upon only 20 minutes of observations, conducted at the time of seed harvest rather than when the harvested stalks flowered.

Conclusions
Numerous articles in journals indicate that bumblebees could have serious impacts on native and agricultural ecosystems on the mainland (see reference list), and the small amount of sound data in the HAL-funded EIS is consistent with this. However, Carruthers, the vice-president of the AHGA stated 'the AHGA would be remiss not to proceed with the application to import bumblebees into mainland Australia'. This contradicts the earlier commitment from the AHGA not to introduce bumblebees unless they are benign, because they did not want to be responsible for another extensive invasion of Australia by a feral organism (Cooke 2001). The position taken by Carruthers parallels that of Reginald Mungomery almost 70 years ago, when he denied the evidence indicating that cane toads would prove harmful in Australia.

Key References
Carruthers S. (2003), Plight of the bumblebee, In: Practical Hydroponics and Greenhouses 69, 23-30.

Hergstrom K., Buttermore R., Seeman O., McCorkell B. (2002), Environmental research on the impact of bumblebees in Australia and facilitation of national communication for/against further introduction. Horticulture Australia Project No: VG99033, Horticulture Australia Ltd, Sydney, and Tasmanian Museum and Art Gallery, Hobart