One more weed has become resistant to herbicides.
Cleavers, a serious weed for prairie farmers, has become resistant to group two herbicides, said Linda Hall, Alberta Agriculture’s weed specialist.
Hall confirmed the resistance in a farm near Ponoka, Alta.
“Because it is cleavers it is a major problem. Cleavers is a very damaging weed where canola is grown,” said Hall.
Cleavers seed cannot be separated from canola because it is similar in size and shape. The weed causes thousands of dollars of loss by cutting yields and lowering grades.
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“Where there is cleavers, and they grow canola, it is very, very bad news,” said Hall.
She was called by an industry rep to look at a field last summer in which cleavers had not been controlled by a herbicide called Unity.
After the cleavers did not show ill effects from the first spray, the producer sprayed the crop with a second herbicide.
“When I got there all I could see was cleavers around the edge of the field and dead cleavers in the barley field where it had been controlled.”
Seed and plant samples were taken from the edge of the field and tested in a lab over the winter.
Nothing will destroy
“What we found is that this cleavers population is resistant to every group two herbicide we’ve tried to control it with including Amber, Refine, Extra and Pursuit.
“I sprayed them at everything from half the label rate to eight times the label rate. Very high levels of resistance is what we found.”
It’s not entirely surprising that cleavers has become resistant to group two herbicides, said Hall. Many weeds that have become resistant to herbicides are resistant to herbicides from group two.
Herbicides are divided into 26 groups based on how they work. Farmers are instructed to rotate herbicides they use in each field to inhibit herbicide resistance.
In parts of the world, some weeds have become resistant to group two herbicides as little as five years after they were introduced.
“Grouping is a simple but effective tool in helping control resistance,” said Len Juras, weed control specialist with Saskatchewan agriculture.
Herbicide resistant cleavers has not yet been found in Saskatchewan or Manitoba. But once one patch of herbicide-resistant weeds is found it is only a matter of time before others pop up across the Prairies.
Hall is in the process of analyzing cleavers seed samples from across Alberta to screen for herbicide resistance. The results should be ready by the beginning of April.
The fact many good cleaver-control herbicides are classed in the group two family is a concern to many farmers, she said.
