[ASC-media] Media release: beating root rot

CRCA Media crcamedia at starclass.com.au
Mon Aug 9 21:09:50 EST 2004


August 10, 2004


Clean boots and hairy vetch are two weapons that cotton farmers can use in the fight against the pest black root rot, according to research by the Australian Cotton Cooperative Research Centre.

Black root rot (Thielaviopsis basicola) affects cotton crops across Australia, and can lead to a twenty to thirty per cent loss of yield, says plant pathologist Stephen Allen.

"There's no single easy solution to black root rot," says Dr Allen. "The CRC has devised a Best Management Practice manual to help farmers develop an integrated control program. One of the best remedies is quite simple: come clean, go clean."

Dr Allen says that in controlled tests farm vehicles, implements, and even farmers' boots have been implicated in spreading the fungus.

"When I first identified black root rot in Australian cotton in 1990, we had no idea where it was coming from - it could even have been a native strain of the fungus, which appears in various forms in cotton growing areas around the world," he says. "Now we have established that the particular strains that we are dealing with are unique to cotton, and are being spread from farm to farm.

"Unfortunately we are also dealing with pathogen-friendly farming systems," says Dr Allen. "Our transport infrastructure, movement of crop residues, and above all our irrigation networks make an ideal environment for the spread of the fungus through the cotton-growing districts."

Dr Allen says that delaying planting may have a good effect, but depends on favourable weather later in the season. Fungicides have little impact, and no fungus-resistant strains of cotton have so far been developed or discovered.

However Dr Allen says that two areas of research are showing promise, now that scientists from the Cotton CRC have definitely established that the fungus is being spread from farm to farm.

"We are developing a two-pronged strategy," he says. "We're getting very promising results from biofumigation, and the pathologists are testing treatments which induce resistance - that is, chemicals which have no direct effect on the fungus, except to stimulate the cotton's own natural resistance to attack."

Dr Allen says that biofumigation has many benefits; by planting a legume green manure crop such as hairy vetch, the farmer fumigates the soil as the vetch plants produce naturally toxic ammonia on breakdown. Vetch has the added benefit of being a nitrogen-fixing plant, so that when the field is cultivated and planted with cotton, it is both free of fungus infestation and is naturally rich in vital nitrogen.

"Biofumigation with vetch means less dependence on chemical fungicides - which so far have been ineffective anyway - and less dependence on expensive chemical fertilisers," says Dr Allen.

According to Dr Allen, there is considerable interest from overseas in Australia's cotton growing strategies, especially in methods of combating black root rot.

"The cotton-growing industry is in some ways a model for Australian agriculture," says Dr Allen, "in particular in the recognition that growers give to scientific research. Our researchers are welcomed and valued by growers, and we in turn rely on growers for help with many of our field studies."

This research project supports Australia's National Research Priority No. 1, an Environmentally Sustainable Australia.

More information:
Dr Stephen Allen, Cotton CRC, 02-6799 1530
Kym Orman, Cotton CRC, 02 6799 1522
Prof Julian Cribb, CRCA media, 0418 634 245

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