Glyphosate-resistant weed confirmed

Eight populations of flax-leaf fleabane (Conyza bonariensis) have been confirmed resistant to glyphosate in northern NSW and southern Queensland.

This is the fifth weed species to be confirmed resistant to glyphosate in Australia in the past 10 years, with four being found in the past three years, and is the first glyphosate resistant broadleaf weed found in Australia.

This should ring alarm bells with no-till farmers and road managers whose heavy reliance on glyphosate as their herbicide-of-choice continues unabated.

Steve Walker of the University of Queensland, whose DEEDI team made the discovery, says growers must be even more vigilant in their spring and summer weed control because these weed seedlings can withstand up to eight times the normal rate of glyphosate. In other words, the glyphosate just won't work, he says.

This species has also developed resistance to glyphosate in South Africa, the US, Brazil, Spain, Colombia and Israel.

Fleabane has become one of the major weeds of no-till farming in Australia through its ability to germinate on or close to the soil surface across a wide part of the year. Fleabane is also a major weed of road shoulders and verges.

In summer it quickly exhibits moisture stress, yet can survive long periods of high temperatures and regrow following rain.

Fleabane can produce more than 100,000 seeds per plant, which are easily spread by wind and water. Fleabane seed has been measured travelling up to 1800 metres from the parent plant; thus resistant plants can easily spread from other areas.

Source: sj.farmonline