A recent decision by the World Health Organization to classify glyphosate as probably carcinogenic to humans may have given the herbicide’s critics more ammunition, but weed scientists say it’s not the end of the debate.
Peter Sikkema, a University of Guelph weed scientist, said he isn’t concerned about the long-term future of the herbicide.
Sikkema, who pointed out that he isn’t a toxicologist, said the weight of science suggests glyphosate isn’t a threat to human health.
“If there are a hundred studies that show that glyphosate is safe to use and there’s one that shows it’s unsafe … I think that glyphosate is a safe molecule to use for weed management,” he said.
“I do not expect it will be removed from the market…. My intuition is that it will remain an effective weed management tool for many years in the future.”
Carol Mallory-Smith, a weed scientist at Oregon State University, said there’s little doubt that the herbicide is becoming more controversial.
“Even without this (WHO) report, there are more and more people, in the public, concerned about glyphosate.”
Campaigners who dislike industrial agriculture and biotechnology have targeted glyphosate because it is applied to genetically modified, herbicide tolerant crops, Mallory-Smith said.
The antagonism toward glyphosate is probably also connected to its dominance.
According to a U.S. Environmental Protection Agency report, glyphosate represented 51 percent of all pesticides used in America in 2007. Mallory-Smith said farmers and the agricultural community are guilty when it comes to over-using the pesticide.
“I’ve certainly spoken out about the misuse of glyphosate … and not using it in a sustainable manner,” she said.
“There are people who are very concerned about using as many pounds as have been used … and what are the (impacts) in the environment.”
Still, Mallory-Smith said restricting or regulating agricultural use of glyphosate would not work.
Sikkema agreed, noting regulations would be impossible to manage and enforce.
“I think we need to change the way we’ve used glyphosate. We’ve overused (the) technology. That’s quite well accepted,” he said. “(But) I’m not a proponent for regulations …. (saying) you can only use glyphosate once every two years on a given piece of ground, or something like that.”
Rene Van Acker, a University of Guelph professor of plant science and a weed management expert, said the WHO decision is troubling, but weeds that develop resistance to glyphosate are probably a greater threat to the herbicide’s future in agriculture.
More than 30 weed species have developed resistance to glyphosate, according to the International Survey of Herbicide Resistant Weeds.
Van Acker said farmers could carry on without glyphosate if the herbicide slowly became less effective.
“If we lost it over time because of resistant weeds … farmers would adapt over time and things would evolve,” he said. “If it was removed all of a sudden, that would be very difficult. We depend on it very highly.”
Mallory-Smith isn’t particularly worried about glyphosate’s future. Farmers would have to alter production practices if it was banned or became redundant because of weed resistance, but it wouldn’t be a full-blown catastrophe.
“We farmed long before we had glyphosate.”