New maps published by OMAFRA suggest Grey County is the only county in Midwestern or Southwestern Ontario without an confirmed herbicide-resistant Canada Fleabane.
The ministry's Mike Cowbrough says they've seen a steady increase in the number of counties in the province with confirmed resistant populations.
He blames it on the use of one herbicide for weed control over several crops and not rotating crops in fields.
"Not a very diverse crop rotation, a focus on one herbicide over multiple years to control weeds, and then you're selecting for ones that are naturally more tolerant or resistant."
By rotating crops, he suggests farmers would need to change-up their herbicides as well as changing their planting and harvesting methods and schedules - all of which help avoid the selection of resistant weeds.
"Farmers know that they see different weeds growing in a winter wheat crop than they do in corn or soybeans. Sure, there's some overlap, but by-and-large you see species that typically you don't see, and that's because weeds planted in the fall by this time of the year it's got good cover and you're going to recruit different weeds to germinate."
Cowbrough says University of Guelph researchers are testing a number of samples sent in by farmers from across the province.
He expects the maps posted on-line will be updated in the next few months to include the results of those tests.
The maps can be found on the Field Crop News website.
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The Ministry's Mike Cowbrough says there's been a steady increase in the number of counties with confirmed herbicide-resistant weeds over the past few years.
[audio mp3="http://blackburnnews.com/wp-content/uploads/2016/03/COWBROUGH-Weeds-1.mp3"][/audio]
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One thing farmers can do is add different herbicides to control the weed they're having trouble with - but Cowbrough says they can also take more long-term steps.
[audio mp3="http://blackburnnews.com/wp-content/uploads/2016/03/COWBROUGH-Weeds-2.mp3"][/audio]
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Cowbrough says crop rotation is one way farmers can help reduce the chance of creating resistant weeds in their fields.
[audio mp3="http://blackburnnews.com/wp-content/uploads/2016/03/COWBROUGH-Weeds-3.mp3"][/audio]
