Credit: Weed CRC

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SYDNEY, 23 August 2006: Australians may lose the battle against the uncontrollable spread of weeds cropping up on farmlands around the country, according to scientists from the Weeds Cooperative Research Centre (CRC).

The increasing resistance of weeds to our most potent methods of control is raising a concerning question: what if there arises a weed that resists all our chemicals and runs out of control?

"We can't afford to let it happen," said Chris Preston, program leader for the Weeds CRC.

Farmers commonly use herbicides to thwart weeds because it they represent the most efficient and affordable method for weed control.

However, thirty-three different species of weeds are resistant to herbicides commonly used in Australian farmlands, according to Preston.

"If there were no herbicides, grain farmers would probably have to revert to cultivation as a means of weed control. This would be a serious environmental disaster and would almost certainly lead to dramatic declines in production as a result of the degradation of the soil," he said.

But when farmers persistently use herbicides to manage weeds for short-term riddance, the weeds begin to build up a resistance.

Currently, more than 70 per cent of grain farmers in South Australia are battling resistant weeds. The same problem is faced in Western Australia, but is speculated to be less serious in the rest of Australia.

This is a long-term problem, according to Preston, because when a weed becomes resistant, it stays resistant forever.

"There has been a bit of an attitude that this can be dealt with next year. We have been arguing that farmers should get involved in population management rather than weed control," he said.

Therefore, the only way to deal with the problem is to manage it.

"It's fair to say that the options for weed control are shrinking, as more weeds develop resistance to the most common herbicides, but with good management this process can be stretched out considerably - and meanwhile new methods are under development," Preston said.

The most significant weeds of Australian cropping systems, such as annual ryegrass, wild oats, wild radish, and brome grass are now becoming resistant, according to Preston.

Of particular interest to Preston, is the resistance in annual ryegrass to glyphosate. "Most people will know this herbicide by its trade name of Roundup," he said.

He said they want the farmers to be able use it into the future.

"The challenge is to develop robust crop production systems where herbicide resistance will not cause the failure of the system. We need to help farmers manage their weed control better so they can remain profitable and on the land," he said.

Currently, weeds cost agricultural industries more than A$3.5 billion per year in costs of control and lost production.

And the consequences will be seen through increased food prices, declining international food trade, intensified dust storms, and uncontrolled surface water run-off.

Looking back at the past 20 years of weed history, he said more and more farmers will be forced to battle herbicide resistance.

"While a number of agricultural weeds were introduced accidentally in the 19th century, many of Australia's worst weeds were introduced deliberately, often for amenity use," he said.