A new broadleaf weed herbicide with a new mode of action is expected to be available to prairie grain farmers next spring.
Field-tested in North America since 2000, and already registered and selling in the United States, pyrasulfotole is the first herbicide in 20 years to feature a new mode of action. It will be sold under the Infinity brand name.
“From the perspective of management of weeds which have become resistant to herbicides, that’s a pretty big deal,” said David Drexler, director of research and development for Bayer CropScience Canada.
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“It’s a new tool. Weeds in Western Canada have never been exposed to this mode of action before.”
Test trials
This summer, over 200 federal research permit test trials were conducted across Canada, and the company has been notified by the government that the product is eligible for registration, he said.
The herbicide, which fits into the Group 27 category, kills weeds in a unique way. Its main action is to prevent the production of carotenoids, pigments that protect chlorophyll from destructive ultraviolet light. Deprived of the means to produce chlorophyll, a weed treated with Infinity bleaches and dies.
“Farmers will like this because within a matter of a half dozen days, the weeds turn white and everybody will be able to tell that it’s working,” said Drexler. “It’s very obvious, very fast and very straightforward.
“Spring wheat, durum and barley break this stuff down so quickly that it doesn’t even have a chance to show a symptom and almost every broadleaf weed of significant economic impact in Western Canada is cooked.”
Fifteen years ago, Bayer launched a concerted effort to devise new herbicide modes of action for cereal crops. Developing a completely new product takes years of research and costs up to $100 million to bring it from the lab to the field, he said.
Tom Wolf, a research scientist at the Saskatoon Research Centre, whose specialty is application technology, said Group 27 products have existed in other markets, but are new to Canada.
(See Herbicide attacks, page 2)
New tools are always welcome, he added, because they offer farmers an opportunity to diversify their approach to weed control.
“There has been a slowdown in the discovery of new modes of action, generally, in the herbicide world,” he said.
“We made some very important breakthroughs in the 1970s and ’80s, but since then we’ve simply added new products to those existing mode of action groups.”
The slow pace of innovation is due to the difficulty in discovering and screening hundreds of thousands of new synthetic molecules, he added.
Also, in Canada, the onus is on the manufacturer to provide not only environmental and toxicological data, but also proof of efficacy. This extra step ensures that the product is effective at the rates listed on the label.
“In the United States, they don’t review efficacy data. They say the marketplace will decide if the product controls weeds usefully or not,” he said.
Barry Mason, who farms northeast of Drumheller, Alta., said field trials with the herbicide on his land this summer showed good results.
“It looked like a good chemical for tank mixing options,” he said, “especially with the weed spectrum I’ve got around here.”
Cost a factor
Mason said that he’ll likely use it next spring, but the degree will depend on how much it costs.
Infinity seemed to do a good job on sow thistle, cleavers, hemp nettle, wild buckwheat and the “good, strong variety” of kochia that has been appearing on his fields in recent years.
Two decades is a long time to wait for new herbicides, he added.
“With direct seeding, we’ve got a whole range of weeds that we’ve never seen before because we’ve created a new environment. Especially when we start throwing in pulse crops like peas and chickpeas. I’m starting to get a wild mess now with sow thistle because there’s nothing to control it in peas.”
