Weed resistance could mean herbicide is futile
- 13 May 2010 by Bob Holmes
- Magazine issue 2760. Subscribe and save
- For similar stories, visit the Food and Drink and Evolution Topic Guides
THE world's most popular herbicide is losing its knockout punch. More and more weeds are evolving resistance to glyphosate - originally marketed by Monsanto as Roundup - but the problem could have been forestalled by farming practices enriched by a better understanding of evolution.
This is a serious problem. "Glyphosate is as important to world food production as penicillin is to human health," says Stephen Powles, a plant scientist at the University of Western Australia in Perth.
In 1996, Monsanto began selling crop varieties genetically modified to contain a gene for glyphosate resistance. This enabled farmers to spray glyphosate - lethal to plants yet non-toxic to animals - on their fields to kill weeds without damaging the crops, even during the growing season.
Today nearly 100 million hectares worldwide are planted with glyphosate-resistant crops. In much of the south-eastern US, as well as Brazil and Argentina, farmers grow glyphosate-resistant corn, soybeans and cotton year after year and have come to rely almost exclusively on this herbicide. This has encouraged at least nine species of weed to evolve their own glyphosate resistance, to the point where some farmers can no longer control weed infestations.
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