Posts Tagged ‘ pollinate ’

Issue 97: Floral arms race seduces insects

November/December – 2007
Author: Anne Gaskett

During National Science Week, ANNE GASKETT reported compelling evidence that native Australian orchids use their colour, shape and fragrance to seduce male insects. Her ground-breaking research has important implications for the control of agricultural pests.

Australian orchids are engaged in an arms race, using sensory overload to seduce male insects. Macquarie University PhD student Anne Gaskett has discovered just how they do it. Her work is important to the conservation of orchids and the control of economically important agricultural pests.

Gaskett has been analysing the smells, colours and shapes of flowers from an insect’s perspective. She has found that orchids mimic female insects so well that male insects cannot resist mating with them and accidentally ferrying pollen from plant to plant.

“I have accumulated the first compelling evidence of an ongoing and escalating arms race between orchids and their unwitting insect pollinators,” Gaskett explains.

“Over generations the insects learn to avoid having sex with orchids, and this means only the most persuasive orchids reproduce, which drives the acceleration of orchid subterfuge.”

The Australian bush is rife with such sexual deception, Gaskett says, as native orchids lure pollinators with false promises of romance.

Gaskett has been studying the hardworking orchid dupe wasp (Lissopimpla excelsa), which is fooled into copulating with not just one, but five native tongue orchid species (Cryptostylis) in urban and regional Australia. All the tongue orchid species mimic the female dupe wasp, but to the human eye they look quite different.

By using modern technology to study the physics of the colours of the orchids and the female insects, Gaskett has revealed that they are identical when viewed by male insects. The flowers are also shaped to mimic female insect bodies.

To the human eyes the female wasp looks orange and black and the orchids are pink, maroon and orange-red. However, receptors in human and wasp eyes are very different. Unlike humans, wasps see ultraviolet light. When Gaskett used a spectrometer to study the wavelengths of light reflected from orchids and female wasps, she was amazed to find they were virtually identical.

“The smell is the most important thing for attracting the insect,” she said. “But the colours say this is the source of that alluring fragrance.”

Gaskett is now looking at the impact of the chemical components of orchid perfumes directly on wasp antennae, to understand what makes these fragrances irresistible.

“The key to the orchids’ success is bombarding young male wasps with an extremely compelling sensory overload of irresistible sex signals,” Gaskett explains.

Studying these intimate interactions addresses big questions about nature and evolution and highlights the millions of other unknown interactions crucial for a sustainable and healthy environment.

“These insects might be fools for love, but their role as orchid pollinators makes them indispensable.”

Gaskett’s next step will be to analyse the seductive orchid bouquets to discover which elements mimic the female wasp pheromones.

So what led Anne Gasket down this research path?
“I’ve always enjoyed getting out and investigating nature,” said Gaskett. “In the past, I’ve focused on animals, studying projects such as Antarctic fish diet around Macquarie Island, and spider mating and sex pheromones.

“When I was designing my PhD research I wanted to expand into botany and learn lab techniques useful for applied research in the future. I wanted a topic that would involve local community groups and enthusiasts plus travel and fieldwork opportunities, and avoid nocturnal animals – I didn’t want to be up all night!

“Studying orchids suited all these requirements and since Australia has most of the world’s sexually deceptive orchids, I thought I was well placed to use local native plants to discover interesting results with some global impact,” she said.

To study the orchids’ scents, Gaskett borrowed techniques from agricultural studies for identifying pest insects, usually very specific sex pheromones.

“If you can identify and make synthetic versions of the pheromones, you can use it as bait to trap male insects so they can’t reproduce or get into the crops,” she said.

The identification procedure is called gas chromatography – electro-antennography. It involves sampling the scent of an orchid, or a female of a pest species, and using gas chromatography to break the scent down into its separate components.

“You attach an antenna from the orchid-visiting insect or pest species so that as the scent is separated, it also blows across the antenna. You can detect when the antenna’s chemoreceptors fire and, therefore, which components are attractive to the insect,” Gaskett explains.

“I’ve used this project as an opportunity to promote and improve my skills with these techniques so the future might see me working in a much more applied capacity.”

Gaskett was one of 16 early-career scientists presenting their research to the public for the first time thanks to Fresh Science, a national program sponsored by the Federal and Victorian Governments. Her work has been funded for three years by a 2005 American Orchid Society Fellowship.

For further information contact:
Anne Gaskett
Ph: 0401 009 328
Email:
agaskett@mq.edu.au

About Fresh Science
Fresh Science is a national competition that identifies new and interesting research being done by early-career scientists around the country. Their stories are released to the media before, during and after National Science Week, which was held in August.

Sixteen scientists were selected from more than 80 nominations. They were flown to Melbourne for a day of media training after which they presented their work to the media, school students, the general public, scientists, government and industry over the course of three days.

Described by some as a boot camp in science communication, previous Fresh Scientists have attracted national and international interest resulting in hundreds of media stories, including national television news. Details of previous winners, their press releases and media coverage can be seen on the Fresh Science website.

Now in its 10th year, Fresh Science is a national event, which brings together scientists, the media and the public. It is designed to:
– Enhance reporting of Australian science
– Highlight and encourage debate on the role of science in Australian society
– Provide role models for the next generation of Australian scientists.

If you are a scientist who was awarded a PhD less than five years ago, have a significant peer-reviewed scientific achievement and think you can tell an interesting story in everyday language, then check out the selection criteria on the Fresh Science website www.scienceinpublic.com for the 2008 Fresh Science competition.

Issue 88: Bumblebees for Pollination of Greenhouse Tomato Crops in Australia

May/June – 2006
Author: Steven Carruthers

STEVEN CARRUTHERS provides an update on the Australian Hydroponic & Greenhouse Association’s application to import bumblebees (Bombus terrestris) onto the mainland to pollinate greenhouse tomato crops Crops in Australia.

Following a review period of 40 business days on the Department of Environment and Heritage (DEH) website to allow the public and industry stakeholders the opportunity to comment, the Australian Hydroponic & Greenhouse Association (AHGA) plans to proceed ahead with its application to allow the import of bumblebees (Bombus terrestris) on to the Australian mainland to pollinate greenhouse tomato crops.

The industry’s application to import bumblebees follows an eight-year investigation including a three-year Environmental Impact Study (EIS) following a national workshop to identify all the issues of concern to various groups, and an independent ‘Climex’ study to identify possible impacts on the Australian mainland. The AHGA engaged one of the world’s leading bumblebee experts, Dr Don Griffiths, from the United Kingdom, whose definitive study of all the key questions posed by both sides of the argument concludes with the following statement:

“If one considers all the facts given, then the case is clearly made to permit the commercial introduction of Bombus terrestris onto mainland Australia.”

Bumblebees were accidentally introduced into Tasmania in 1992. Although they have spread throughout the island State, studies have shown that they are mainly found in urban areas rich in imported floral species, the preferred plants of bumblebees. The EIS study found no adverse impacts to warrant their exclusion from the mainland to pollinate commercial greenhouse tomato crops.

“Bumblebee technology is available to almost every country on the planet except Australia.”

Currently, growers pollinate their tomato crops three times a week using mechanical hand-held vibrators touching each plant. The industry estimates that it costs Australian growers $25,000 to manually pollinate 1 hectare (10,000sqm) of tomatoes, against $7,000 for bumblebee pollination, a saving of $18,000 per hectare. This is a 72% saving or in excess of $8 million annually industry-wide, as well as improving tomato yields, quality and shelf life. Without bumblebee technology, Australian greenhouse tomato growers say they will be unable to compete with cheap tomato imports.

“Bumblebee technology is available to almost every country on the planet except Australia,” said AHGA President, Mr Graeme Smith.

“Pressure from NZ imports, with recent approval for importation of Dutch produce, and with Chinese imports on the horizon, means that if the industry hopes to match production standards with our international competitors, all of which use bumblebees, then access to this technology is mandatory.”

Mr Smith said: “The industry is not proposing to release bumblebees into the Australian environment. They will be confined to sealed greenhouses within hives specially fitted with a queen excluder device that allows only non-breeding worker bees into the crop. The technology is currently used in the USA and Canada to prevent the eastern bumblebee species, Bombus impatiens, from establishing in the west of that continent.

“On the basis of existing knowledge and climate restrictions, in the unlikely event of escape or accident, the AHGA predicts any chance of bumblebees establishing in Australia’s harsh environment to be very limited and transient,” said Mr Smith.

“Spurious claims that bumblebees are another cane toad or fox are clearly false.”

According to the industry’s research, bumblebees prefer exotic (introduced) plant species (90%), compared to native species (only 10%); therefore, there is little likelihood of any competition for floral resources.

Mr Smith added: “Spurious claims that bumblebees are another cane toad or fox are clearly false,” and he cited many positive examples of species imported into Australia such as the leafcutter bee, European honeybee, sheep, cattle, brown trout, and even the dung beetle without which inland Australia would be a mess. While Australia has its own native dung beetle, it simply can’t cope with the tonnes of dung expelled by imported animals on a daily basis. The dung beetle is also a friend in the cities of Australia, ridding parks of tonnes of dog droppings that occur every day.

Returning to bumblebees, the AHGA proposes to import only certified pathogen and parasite-free bumblebee stock from reputable producers. Mr Smith said that any parasite or pathogen that has been associated with Bombus terrestrisis unique to bumblebees and poses no risk to Australian honeybees or native bees.

“Despite the gloom and doom scenario painted by a few individuals, no adverse effects have been shown there.” (in Tasmania)

The industry’s detailed report points to previous releases of bumblebees on the Australian mainland in the 1800’s and 1900’s that failed to colonise. Although there were no studies conducted on these releases, Australia’s harsh climate and lack of all-year-round floral resources, are thought to be contributing factors why they didn’t colonise. In their native distribution range, bumblebees are only found between latitude 60°N and 30°N, which helps explain why they have established in New Zealand and Tasmania which enjoy similar climates. Ants are also thought to be a contributing factor for the failure of previous bumblebee releases on the mainland to colonise. Unlike honeybees that build their hives above the ground, bumblebees are ground nesters, usually in damp areas.

In the event that bumblebees do establish on the mainland, an AHGA-funded Climex study indicates that any distribution will be confined to the cooler, wetter areas and limited to Victoria, just over the NSW border, and the southwest corner of WA.

“First reported sightings of bumblebees in Tasmania, which has a much more suitable climate, were around 1992,” said Mr Smith. “Despite the gloom and doom scenario painted by a few individuals, no adverse effects have been shown there.

“Bumblebees have been present in New Zealand for over 100 years, and are popular with farmers and public alike. Over this time there have been no definitive examples of any negative effect on that country’s native flora and fauna, and reports of a negative impact in Israel and Japan are false, having been based on poor and limited research,” said Mr Smith.

“The threat to the survival of the Swift Parrot has everything to do with land clearing, wood chipping and habitat destruction.”

Mr Smith added that any threat to endangered Australian birds is pure speculation. While there has been some suggestion that bumblebees are a threat to the survival of the Swift Parrot, the EIS has shown a low bumblebee visitation rate (2%) to favoured blue gum flowers, compared to 56% for honeybees and 25% for birds.

“The threat to the survival of the Swift Parrot has everything to do with land clearing, wood chipping and habitat destruction,” he said.

Overseas experience has shown that bumblebees work long hours and have a high flower visitation rate, around 450 flowers/hr. They buzz pollinate, can tolerate the physical conditions existing within a commercial greenhouse, are housed in trouble-free hives suitable for delivery to growers, breed in sufficient numbers to provide the correct ratio of bees to open flowers (240,000 flowers/ha/week), and are available 52 weeks per year.

“Can they (blue-banded bees) be reared cost-effectively, 52 weeks a year?”

Mr Smith said that while native bee research is encouraged, the industry must be practical. Current research to develop a commercial solution using native blue-banded bees is now in its third year, and still a long way from developing economically viable commercial hives for pollination.

“Will this ever be accomplished, and if so, in what time frame 5, 10, 20 years,” questioned Mr Smith. “Can they ever hope to meet the requirements of a rapidly developing and expanding high technology industry? Can they be reared cost-effectively, 52 weeks a year? How much research money will be needed, with the possible result of no suitable alternatives at the end of it all?”

Although native bee researchers have been successful in breeding small numbers of blue-banded bees using clay and brick mortar nests in the greenhouse, it is not economical to ship mortar hives around the country. Researchers speculate that growers will maintain mortar hives within their greenhouse, which will be replenished regularly; however, the growers I have spoken to say they are simply replacing one labour cost for another and it is unlikely they will maintain permanent hives. By comparison, bumblebees are delivered in cardboard boxes which come with feeders for the life of the artificial hive – for bluebanded-bees, growers will be required to replenish feeders strategically located throughout the greenhouse. For bumblebees, all the grower is required to do is position the hive and open the cardboard entry/exit flap.

There is also a concern about the unusually large breeding area (5,000sqm) required to supply the entire hydroponic greenhouse tomato industry with fresh native bees on a monthly basis. The industry is currently going through expansion with at least another 24 ha of greenhouse production area due to come online during 2006. Presumably, this breeding area would need to expand to meet the future demand of the industry.

There are still many questions to be answered, and no certainty researchers will be able to deliver a commercially viable native bee alternative to bumblebee technology; if at all.

The AHGA believes it has a strong case for allowing the distribution of secure hives of B. terrestristo mainland greenhouses, and it hopes that the misinformation campaign against bumblebees will not prejudice the final outcome. To date, conservationists have been running a strong campaign against the application and they have succeeded in having the bumblebee listed as a ‘Key Threatening Process’ in Victoria and NSW; however, the Federal Government declined to support their application due to “insufficient evidence to support the claim”.

There have been public claims reporting that bumblebees are a pest in other countries, whereas a search of the scientific literature shows that the bumblebee is not regarded as a pest anywhere in the world. ABC Landlinealso incorrectly reported (12 February) that the Australian Quarantine InspectionService (AQIS) had already rejected an application to import bumblebees, when the application submitted by the AHGA is still with the DEH and has not yet been passed on to AQIS. These incorrect reports should be of real concern to industry for the success of its application.

Cost:benefit calculation
Bumblebees are very efficient pollinators. They can deliver up to a 28% increase in production in ideal conditions, at a cost of only 1% of production. If we assume even 10% improvement, then growers can make their own calculations:

Greenhouse size x Average Yield per m 2 x Average Gross Return per kg x 10% = improved yield by bumblebees.

Sample calculation for 4000sqm:
4,000 x 45kg/sqm x $3.00 x 10% = $54,000
Plus labour savings above – 4,000 x $1.80 = $7,200
Total saving = $61, 200

NOTE: These costings do not factor-in improved working conditions and worker safety that can flow on from the use of bumblebees.

About the author
Steven Carruthers is the Managing Editor of Practical Hydroponics & Greenhouses magazine and Vice-President of the Australian Hydroponic & Greenhouse Association. Email: casper@hydroponics.com.au  Ω

PH&G May/June 2006 / Issue 88

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