14 November 2001
Resistant weeds found in gene crops

By Andrew Swallow

WEEDS resistant to glyphosate have been identified in crops of genetically modified herbicide-tolerant maize and soya in the USA.

Resistance problems are predicted to increase, Michael Owen of Iowa State University explained to delegates at the British Crop protection Conference in Brighton om Wednesday (14 November).

But a simple change in herbicide use should offer a solution, he said.

“I dont see the shifts or establishment of resistant populations is going to be a big issue.”

Using an alternative mode of action should solve the problem. But the number of new modes of action becoming available is decreasing, he notes.

Over-use of glyphosate in GM crops is to blame for the rapid shift in resistance of common waterhemp and horseweed, he believes.

One or two applications would often be enough to give economic control of weeds in most GM herbicide tolerant crops.

But growers frequently use three or even four applications to keep fields cosmetically clean, he says.