CAMROSE, Alta. – For the first time, weeds resistant to two groups of herbicides have been found outside Manitoba, said Alberta Agriculture’s weed specialist.
A Camrose farmer discovered in his field a patch of wild oats resistant to two types of herbicides, said Linda Hall.
“The thing that is different about this particular wild oat is that it is resistant both to group one, Assure, and to a group two, Assert,” said Hall.
There have been reports of grassy-type weeds becoming resistant to one group of herbicides in Alberta, but this is the first reported case of a weed resistant to two herbicide groups, said Hall.
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“We don’t know the reason that this is cross resistant or multiple resistant. It is a concern because it leaves very few herbicide options for the producer,” Hall said.
Group one herbicides work by inhibiting fatty acid production in weeds. Group two herbicides work by inhibiting the production of certain amino acids.
While it’s always a surprise to find the first weeds resistant to two herbicides, it was only a matter of time before resistant weeds were found, said Hall.
“Certainly it is a trend worldwide. It is certainly something we have been anticipating.
“I think we’re going to see more and more of these cases where there is resistance in more than one herbicide.”
Herbicide resistance develops when a farmer uses the same herbicide, or herbicides within the same group year after year. While the herbicides kill the majority of weeds, there are always a few naturally resistant weeds. These weeds grow and flourish.
Small patches easily controlled
Hall said if farmers catch the weeds while they are in a small patch, the new resistant weeds can be controlled. Once they’ve spread across the field it’s a more difficult problem.
“For that farmer, he has drastically reduced his herbicide options for wild oats. Now we don’t know if his wild oat is resistant to all group one herbicides and all the group two herbicides because we have not done the tests. But certainly it calls into question whether he’ll be able to use any of the herbicides in those groups,” she said.
Hall said more farmers are going to find similar problems, since reports suggest producers aren’t varying the herbicides they use.
“We need to get the message out to do preventative measures. Farmers need to continue to rotate their herbicides and use alternate control methods to keep their weed numbers down.”
Alberta Agriculture in conjunction with the Environmental Centre in Vegreville, Alta., will begin a program this year to look for more resistant weeds. They also plan to launch an education program to remind farmers to rotate herbicides.
