Glyphosate: victim of success

Harry Strek, leader of Bayer CropSciences integrated weed management and weed resistance biology team in Germany, said a global rise in resistance to glyphosate caused by overuse of the herbicide had thrown a challenge out to chemical manufacturers to find the "next big thing" in weed control.

Dr Strek spoke at a pesticide chemistry conference in Melbourne recently.

Speaking after the conference, he told The Weekly Times that chemical companies needed to invest in research to find broad spectrum herbicides with new modes of action to attack and kill weeds.

"Glyphosate was the herbicide of the century," he said.

"Our industry has not introduced a new significant mode of action (in weed control) in 20 years.

"We need new herbicides and they need to be cheap."

Glyphosate resistance in some weeds has become a problem in many countries.

Resistance has been exacerbated by the uptake of Roundup Ready crops around the world as growers come to rely on a single herbicide for weed control.

Some scientists are predicting half of the worlds agricultural weed species will become resistant to glyphosate by 2018.

Research by the University of Western Australia has found Australia has one of the worlds highest levels of weed resistance per hectare of agricultural land.

Dr Strek said the US had huge problems with resistance to glyphosate, largely related to the use of Roundup Ready corn and soyabean crops.

"Overuse of one herbicide will select for plants which have mutations," he said.

"We estimate 15 to 30 continuous herbicide applications will eventually lead to resistance.

"So it is important to mix the herbicide modes of action.

"Farmers should use another (mode of) chemistry every other year or every third year (for weed control)."

Dr Strek suggested farmers use other pre-emergent or post-emergent herbicides in rotation with glyphosate, even though the other chemicals might not be as effective.

"And if possible, rotate the types of crops," he said.

"Basically, avoid the over-reliance on one mode of action because weeds can develop resistance to any herbicide if it is overused."

Source: The Weekly Times