WEED resistance to glyphosate-based herbicides is the greatest present threat to world food production, according to international authority Stephen Powles.
But there is good news for Australian farmers, particularly WA farmers, because they have learned valuable lessons from Australians who previously led the world in weed herbicide resistance, according to Professor Powles, who is a director of the Australian Herbicide Resistance Initiative at the University of WA's School of Plant Biology.
At the GRDC Grains Research Update in Perth last week the Quairading farmer described glyphosate, in agricultural use since 1974 as the main constituent in the Roundup range of herbicides, as the "world's most important herbicide", as "important to world food production as penicillin was and is to world health".
But its effectiveness and ease of use had led to it being overused and over-relied on to control weeds around the world, he said.
"Herbicide resistance is occurring all around the world, it's occurring every place that herbicides are overused.
"We (Australia) used to be number one in the world for herbicides resistance but we've lost that dubious distinction to the United States, it's now number one in the world for herbicide-resistant weed infestation."
Professor Powles said 1996 adoption of Roundup Ready or glyphosate-tolerant crops in the US was the fastest adoption of any agricultural innovation anywhere in the world.
But almost total reliance on glyphosate had seen emergence of resistant weeds which have a significant impact on the two main rotation crops, corn and soybeans.
Of the 36 million hectares planted annually to corn or soybeans, glyphosate resistance had been reported in up to 94 per cent.
In the south, cotton was added to the rotation and, from 2010, of the total 70mha corn, soybeans and cotton production areas, farmers were reporting glyphosate resistance over 34mha.
"This is the most important food producing region on the planet," Professor Powles said.
"The US is still by far the world's greatest grain exporter and what happens in that part of the world influences everything in the world.
"In the past they had up to seven modes of action and up to 43 different herbicides to combat weeds but by 1996 they were back to one, only glyphosate.
"US farmers before glyphosate-resistant weeds were spending $75 a hectare to grow corn and now with glyphosate-resistant weeds, they are spending $200.
"With soy beans the cost has grown from $75/ha to $250/ha.
"Take that with the commodity price drop that has occurred in the US and the US farmer is hurting in a way they have not previously."
Professor Powles presented a similar picture for Argentina, Brazil and Paraguay and Uruguay.
"You end up with 50mha of the world's best crop land infested with weeds resistant to glyphosate and to herbicides used earlier and that's a threat to global food production."
Professor Powles said results of a 2015 random survey of WA paddocks to test glyphosate resistance would start filtering through this winter.
The last random survey of 500 cropping fields in 2010 and a 2010-11 survey of 239 Roundup Ready canola fields indicated a ryegrass resistance developing in up to 7pc of fields.
He said this was worrying given ryegrass was Australian agriculture's second top pest weed.
But, the good news was other weeds such as wild radish, wild oats, brome, barley grass and marshmallow showed no resistance developing.
"This is unequivocally good news and if you happen to be in that 93pc you should do everything you can to keep glyphosate working," he said.
"We need to diversify away from glyphosate if we want to keep the world's greatest herbicide working in agriculture."
Seeding techniques to counter weeds included the "double knock" using different types of herbicides, delayed seeding and high seeding rates.
East-west planting was also popular because emerging crops shadowed and suppressed weeds, Professor Powles said.
The Harrington Seed Destructor (HSD) was also seen as an important tool and a local manufacturer had just been announced for integrated, in-header HSD technology, he said.
A Sydney University research team had also just proved its seed kill efficiency at 93pc for annual ryegrass and 99pc or better for wild radish, wild oats and brome.
Three companies in Germany, the US and Britain were working on sensor-controlled precision spraying systems to identify and deal with weeds in crops.
"One of them is integrated into the spray boom, it can operate at up to 12kmh and it operates independently of a light, it's not using infrared.
"When we can use chemicals to spot spray in crop, it's a paradigm shift, that's a game changer and it's due to hit the market within 12 months."