A new weed is taking root in Manitoba, posing a triple threat to producers who find it on their farms.
Last fall, researchers pulled eight samples of wild oats resistant to herbicides from Groups 1, 2 and 25 from fields in the northwest region.
“I think it’s very, very serious for the producers who are dealing with it,” said weed specialist Dave Kelner.
“It really eliminates probably 95 percent of the herbicide options that these producers would have been used to having at their disposal.”
Herbicide resistance is nothing new for Manitoba farmers, who have found stubborn patches of green foxtail, wild mustard, hemp nettle, chickweed and kochia in the past.
Read Also
Farm Credit Canada partners with major Toronto innovation hub
A FCC parntership with MaRS Discovery District aims to solve technology problems in food supply chains.
Chemicals involved
Wild oats resistant to Group 1 type herbicides are widespread. In 1995, researchers found wild oats that could not be killed by either Group 1 or Group 2 chemicals.
Doubly resistant wild oats have also been found in Saskatchewan and Alberta.
In 1994, four samples of the triply resistant weed were found in the Swan River Valley. Last August, Kelner and other weed specialists found 14 more.
University of Manitoba researchers tested them for resistance to Poast and Puma/Triumph Plus (Group 1), Assert (Group 2) and Mataven (Group 25).
All samples were resistant to at least one of the groups, and more than half were resistant to all three.
Kelner said wheat growers who face the triple resistance spectre have two chemical options left: Avadex and Fortress.
“The other two are soil-applied products, which really aren’t the products of choice,” he said.
“A lot of producers like to use the post-emergent types, the ones that you spray after the crop is up.”
Avenge would be another option for multiple resistant weeds, but it will not be available for at least a year. Manufacturer Cyanamid is looking for another factory to make the herbicide.
Kelner said the triple resistant wild oats have not yet been found in Saskatchewan and Alberta. However, wild oats resistant to Groups 1 and 2 herbicides have popped up.
Farmers are aware of resistance and understand how to avoid it. But Kelner said sales of Group 1 herbicides show farmers aren’t necessarily putting their knowledge into practice.
Last year, Group 1 herbicides took 70 percent of the grassy weed herbicide market in Manitoba, and set a new sales record. Had farmers been rotating herbicides, the products should have accounted for about a third of the total market.
“The fact that record was broken shows that herbicide rotation, which is really one of the main methods that a producer would use to manage resistance, … hasn’t been adopted to the extent that it should be,” Kelner said.
Final resort
“I think when push comes to crunch in June, they often end up resorting to the Group 1 products because of their flexibility and convenience and performance.”
Farmers using Assert and Mataven this year should realize wild oats may resist the chemicals.
Kelner said there are several instances in which farmers should contact provincial agricultural workers or chemical dealers:
- If a patch of wild oats is roughly circular, dense and doesn’t look like a spot missed during chemical spraying.
- If spraying conditions were ideal and the product was applied at the right time and rate and the weeds persist.
- If other weeds within the wild oat patch were killed.
Kelner said he hopes to do a more extensive survey across the province for the triple resistant weeds this summer.
