More weeds now resistant to glyphosate in Australia

Weed scientists are alarmed by a growing resistance in weed populations to one of the farming industry's most powerful herbicides.

Queensland researchers have confirmed the first-ever case of glyphosate resistance in a broadleaf weed in Australia.

Infestations of glyphosate resistant "flax-leaf fleabane" have been found in Northern NSW and southern Queensland, representing the fifth weed to develop resistance in the past decade.

Four of them have been confirmed in the past three years.

Fleabane is one of the biggest weed problems for no-till farmers. One plant can produce more than 100,000 seeds, which can travel 1.8 kilometres and germinate on, or close to, the soil surface, almost all year round.

Data shows resistant fleabane plants can withstand eight times the normal rate of the chemical without dying.

Principal research fellow in weed management with University of Queensland, Dr Steve Walker, is urging farmers to use glyphosate more judiciously.

"They need to look at alternatives to glyphosate. The most effective way of treating weeds on fallow country is to use the 'double-knock' tactic," he said
"There are still weeds that glyphosate will work on, so you'll still probably use glyphosate mixed with 2,4-D, and then come in a week or so later with a paraquat treatment, provided you get the weeds while they're young."

Dr Walker says his team expects other weed species may have already developed, or will develop, resistance and we just don't know about it yet.

"There could be other weed species, particularly grasses, that will develop glyphosate resistance. I suspect they may be there and it's just a matter of knowing where they are and getting samples and getting them tested.

"We've relied on glyphosate for fallow weed control for the last 20 years, and it's been pivotal to allowing us to move towards much more sustainable cropping systems.

"There hasn't been a replacement for glyphosate come onto the market, so it's worth spending a bit more money so we continue having this valuable resource into the future."

Source: abc.net.au