EDMONTON -ÊWhen farmers pay their herbicide bill, they probably wonder if they will ever win the fight against weeds on their farm. But a new survey shows the number of weeds on the Prairies has dropped dramatically since the 1980s, says an Alberta agronomist.
In the 1980s, about 43 percent of prairie fields in a random survey had at least one area that was weed free.
In 1997, the number of fields with weed-free areas had increased to 60.8 percent. In 2001, the number of fields with weed-free areas had increased to 66.7 percent.
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“I’m really proud of our farmers. They have done a very, very good job,” said Denise Maurice, a senior agronomist with Westco.
“All these innovations have done a good job. We have made huge inroads,” said Maurice. She credits zero tillage, new herbicides and farmers’ ingenuity as reasons why weed-free areas in the prairie survey had almost doubled.
The fight against the yield-sapping weeds has not ended. As farmers change the way they farm, so changes the mix and complexity of weeds, Maurice told farmers during FarmTech, an agricultural conference.
“Some of the weeds can change cropping practices and some cropping practices can change the weeds.”
Twenty years ago, weeds were controlled by a combination of tillage and chemicals. As tillage has been reduced, farmers have relied more on chemicals. Overuse of some products has caused some weeds to develop resistance to the more common herbicides. Others have simply changed the timing of emergence to fight extinction.
“They’re adjusting and shifting with the conditions we provide them with,” Maurice said.
Besides changes in existing weeds, researchers have also noticed new weeds on the Prairies.
Japanese brome, which mimics winter wheat production, is on the increase in southern Alberta. Wild pansy or field violet has been spotted in cropland as far north as Lamont, east of Edmonton. In Manitoba, one of the emerging weeds is Virginia ground cherry with seeds the same size as soybeans, a relatively new crop in that province.
The species on the increase are American dragonhead, Canada fleabane, absinth, pasture sage and white cockle, weeds farmers hadn’t even heard of 20 years ago.
Maurice said it’s important for farmers to catch these weeds while they are still small patches in the field. The key to controlling the new weeds is to look past the easy choice glyphosate as spring or fall burnoff and try other options.
“We need to explore the whole environment,” said Maurice who suggested farmers look at different tank mixes of chemicals and different times of year to spray the weeds.
“First, monitor the problem and then choose the best solution and not just automatically use a half or one litre of glyphosate. It’s all about timing. It’s really important we don’t overgeneralize.
“I want you to save that tool (glyphosate) where it will help you the most.”
The top four weeds across the Prairies are familiar to most farmers. Wild buckwheat has become the No. 1 weed on the Prairies. Second is wild oats and herbicide-resistant wild oats, third is chickweed and its herbicide-resistant form, while fourth is Canada thistle, which has jumped from 11th spot.
