Grains Research and Development

Date: 01.11.2001

Crop detectives comb world for friendly killers by Ross Andrews

Above: Bio-control on wild radish: attack of a fungus brought back from Tunisia by Dr John Scott. Left: Dr John Scott,  Officer-in-Charge of the CSIRO European Laboratory, Montpellier, inspecting the impact of bio-controls on wild radish and canola plants.

A LONG, thin 'crop protection fortress ' of science circles the world, helping defend Australia's grain industry from thousands of invasive weeds, pests and diseases.

You find one of its far outposts in a technology park near Montpellier in the south of France. There, in an Australian laboratory, John Scott and his eightmember CSIRO research team work as members of the world's biggest biocontrol collaboration. This draws together elite teams from three continents and includes many Australian-based scientists in CSIRO and the CRC for Australian Weed Management.

Science of bug wars

Bio-control uses the natural enemies of invasive weeds and pests to control their spread in the environment, reducing their impact on the productivity of livestock and crops - where they cost farmers billions of dollars a year.

For example, wild radish is common in most parts of the Australian grain belt, costing farmers about $10/ha - or a quarter of all spraying costs. Over 4 million hectares of infestations are sprayed each year.

Of all countries, Australia is most at risk, as our agriculture is based on crops from every other arable continent, and we generally grow our crops "naked" - without their natural insect and fungal defensive systems ... left behind in their original environments.

In a project to redress this against wild radish, Dr Scott and the CSIRO team in France receive support from Australia's graingrowers and the Federal Government through the Grains Research and Development Corporation (GRDC) and the CRC for Australian Weed Management.

They work like detectives, piecing together biological and geographic clues. "What's this weed related to?" they ask. "Where did it come from?" "What's killing it in its home environment?"

Deadly solutions to many of Australia's worst crop invaders 'are in the sights of the Australian team in France. Solutions have been and are being found for:

  • wild radish (which costs the grain industry $40 million in herbicide a year)
  • skeleton weed
  • doublegee (three-cornered jack)
  • Mediterranean snails, and
  • green vegetable bug (which attacks sorghum).

Virtual bug wars

The CSIRO team in France also fights the crop-invader battles of the future, doing this in miniature, at the laboratory scale - long before the invaders reach Australia.

The team sets out the best strategies for protection against the world's worst cropping pests, such as Russian wheat aphid, which exploded out of its native territory in southern Russia and eastern Turkey two decades ago, to infest 15 countries in about 10 years - cutting yields in South Africa and parts of the US by as much as 90 per cent.

If it arrives, it could devastate Australia's wheat and barley crops in areas subject to drought and moisture stress.

Just as detectives may have a l-in-5 chance of convicting a criminal in a complex crime, Dr Scott rates the chances of successfully introducing a bio-control agent at 18 per cent from the start to finish of each case. Progress, however, has tended to be measured in decades.

Genetic aids like DNA fingerprinting, which are increasingly common in Australian crop science, are considerably increasing the speed and accuracy of research teams.

Speeding up research work can be remarkably simple, as Montpellier technician Janine Vitou found. She was studying the fertility of particular wild radish plants - laboriously opening their rock-hard pods by hand, with wirestrippers.

Instead, she took the wild radish pods to a breast screening clinic in Montpellier. This immediately produced 'photo' images of the insides of hundreds of podsand their seeds, for a cost equivalent to AU$7.

The French screening clinic now saves days of labour by technicians, giving them a god-like ability to see instantly which plants have infertile, stressed, empty or aborted seeds - or have been eaten - all vital clues to speed the search for the most powerful hostile agents against Australia's wild radish scourge.

Going back to ground zero

With their DNA fingerprinting technology Dr Scott said his team works as "phylogeographic detectives". They have to find the point of origin of each crop pest and weed, not just that of their near relatives (which are affected differently by hostile agents).

DNA fingerprinting of pests at Montpellier is by Jean-Francois Martin, who collaborates with two other molecular scientists, who work next door in the US Department of Agriculture'S Agricultural Research Service laboratories.

Together, the US and Australian laboratories negotiate significant volume discounts in the gene-sequencing costs charged by French companies.

Significantly, for the survival of the CSIRO laboratory, some of its external income now comes from US projects such as research into a control for a pest that threatens America's fruit crops, a mealy bug that is thought to come from northern Australia.

Not so wild in Africa

Precise identification of a species (or 'hidden' species) of wild radish takes the Australian scientists to sources of origin around the western Mediterranean Sea from the Montpellier area to Tunisia.

It is common, Dr Scott said, to find that at its African source of origin a subspecies of wild radish will be "struggling to survive". A midge of the Cecidomyiidae family will gall flowers to stop them making seeds ... the flowers are also destroyed by beetles ... sawflies attack the seed pods ... and other beetles follow them to suck the seed pods dry ... Nevertheless, the wild radish still manages to set seed.

Ants then climb the plant to chop down the seeds, eating 65 per cent or more of those that fall to the ground ... soil organisms go on to finish the rest of the job. In many of its places of origin, wild radish appeared unable to replace itself in some seasons.

The CSIRO scientists collect hundreds of these hostile agents, bringing them back to Montpellier for precise identification, and to check that they don't pose a threat to Australia's commercial crops and native species.

A few dozen 'hot suspects' in the war on wild radish were eventually isolated: Dr Scott has one type of gall fly that prevents seed-setting, the larvae of a beetle that attacks seed, weevils of the root and stem, sawflies and 12 diseases.

In the next year, technicians Janine Vitou and Mireille Jourdan, the laboratory 's phytopathologist, will concentrate on the small flies and fungi that attack wild radish. Recently, Ms Vitou also worked on a GRDC-supported project to rear flies that parasitise Mediterranean snails and she hel ped researcher Dean Baker, who received a GRDC travel award to study a parasitoid of aphids at Montpellier.

Calling all killers

At their five Montpellier experimental sites, the CSIRO scientists run trials to attract the deadliest of local fungi and insects to wild radish - helping them understand how all elements of the ecosystem affect the weed.

Recently, the Montpellier wild radish detective team was boosted by leading Australian crop protection scientist Deirdre Lemerle from the CRC for Australian Weed Management and NSW Agriculture. Dr Lemerle combined a holiday with a freelance weed survey-mapping every stand of wild radish along hundreds of kilometres of French roads, along with intelligence reports on their hostile insects and fungi.

When the best bio-controls for wild radish have been found they will be transferred to Australia - probably for further high-security, quarantined research at the CSIRO's new $5 million Perth Containment Facility. Final clearances for public release will take several years and involve approvals by 21 Australian research, government and environmental organisations.

As for the spread of the bio-control agents across Australia's grainbelt, Dr Scott believed this could be extensive and rapid in the case of tiny flies and fungi that are carried by wind.

Left: Ms Mireille Jourdan, phytopathologist, researching bio-controls: rust attacks on blackberry. Shown with 'Genotype 32', the main Australian blackberry, which quickly grows to 10 times the size of normal European species. Above: Wild radish bio-control candidates: insects collected from Europe, the Middle East and Africa. Below: Rust spores forming on the blackberry 'Genotype 32'. Right: Dr John Scott, OIC of CSIRO, Montpellier, on the

Left: Ms Mireille Jourdan, phytopathologist, researching bio-controls: rust attacks on blackberry. Shown with 'Genotype 32', the main Australian blackberry, which quickly grows to 10 times the size of normal European species.

Above: Wild radish bio-control candidates: insects collected from Europe, the Middle East and Africa.

Below: Rust spores forming on the blackberry 'Genotype 32'.

Right: Dr John Scott, OIC of CSIRO, Montpellier, on the "Friendship Bridge" between CSIRO Montpellier and neighbouring US Department of Agriculture Agricultural Research Service (ARS) laboratories.

Program 3.3.3 Contact: Dr John Scott +33467593109