A novel way of controlling herbicide-resistant weeds has emerged from Down Under, but whether it will take off in Canada is still up in the air.
“We know that herbicide resistance is a problem here, but it’s also a really big problem in Australia,” said Breanne Tidemann, a graduate student at the University of Alberta.
“They’ve gone to something called harvest weed seed control to manage the seeds at harvest time.”
Australian farmers have resorted to chaff carts, direct baling, and narrow windrow burning to control weed seeds from annual ryegrass and wild radish, which is resistant to 11 herbicide modes of action. But the most promising tool is the Harrington seed destructor — a tow-behind machine that collects weeds and grinds their seeds at harvest, cutting weed emergence the following year by half in Australian trials.
And researchers at Agriculture and Agri-Food Canada have gotten their hands on one of these units.
“But before we can start testing it, we need to know what weed seeds are still on the plant at harvest time and where on the plant they are produced,” said Tidemann. “Are they at a height where we can go through with a combine and collect the majority of those seeds?”
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Weeds that drop their seeds early or produce seeds too low on the plant likely won’t work with the Harrington seed destructor. Researchers in Lacombe are testing two different crops — wheat and faba beans — at two seeding rates to see if canopy density has an impact on how tall weeds grow and at what height they produce seeds.
“If we have a more open canopy and we’ve got more light penetration, is that changing where the weed seeds are growing in terms of height and where they’re producing their seeds in terms of height?”
The double seeding rate in faba beans has produced plants that are “substantially taller” than those at the recommended seeding rate, creating more competition for faba plants and weeds alike.
“We’re thinking that, if there’s that type of competition, the weeds will also stretch more and… have a difference in where they’re producing their seeds.”
During harvest, researchers will collect volunteer canola, wild oat, and cleaver plants at different cutting heights to see what proportion of seeds are produced at each height, as well as how many seeds remain on the plants. This will help them identify which weeds Canadian growers should target with the Harrington seed destructor.
Wild oats, for instance, will “likely not” work, said Tidemann, because of the timing of their seed production, but the machine shows promise for cleavers.
“If you go through at harvest time, usually the seeds end up sticking to you, so they’re still on the plant,” she said.
While the Harrington seed destructor has had an uptake in Australia, Canadian producers have so far balked at its $120,000 price tag. But as herbicide resistance grows in Canada, producers may need to do things they don’t want to do, said Neil Harker, research scientist with Agriculture and Agri-Food Canada.
“A lot of guys say they don’t want to pull one of these behind their combine,” said Harker. “But in Australia, there are a lot of guys pulling them behind their combine because they have to.”
“They don’t have any other choice,” added Tidemann.