- Ontario repository of herbicide resistant weeds
- Testing services for suspected herbicide resistant weeds
- Ontario counties with confirmed herbicide resistant weed populations
- Testing services for suspected herbicide resistant weeds
- Ontario expertise in herbicide resistance
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RESISTANT WEED TESTING RESULTS SINCE 1998
An online repository of all herbicide resistant weed testing results since 1998 can be found here. Users will be able to search for herbicide resistant weed species and create distribution maps.
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TESTING SERVICES FOR HERBICIDE RESISTANT WEEDS
There are two testing solutions available in Ontario. The plant bio-assay service offered by the Tardif lab at the University of Guelph requires that mature seed is collected in the fall and submitted. Plants are then grown from that seed and sprayed at various doses of the herbicide(s) suspected. Results are provided typically by March, the service is provided at no cost to Ontario farmers. The molecular testing service, requires plant tissue that is roughly “quarter sized”, so a single leaf is often adequate. Results can be obtained within a couple of weeks, but it is a fee based service. Fortunately, there is a funded surveillance project that will process samples at no cost. A sampling protocol for this project can be downloaded here. - Free plant bioassay testing by the University of Guelph
- Molecular testing by TurnKey Genomics (private lab)
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RESISTANT WEED SPECIES BY COUNTY
In Ontario there are 22 different weed species that are resistant to one or more herbicide groups. The table below contains all records of confirmed herbicide resistant weed species in Ontario since 1981 (as of February, 2021)
Weed species confirmed resistant to a herbicide group by county in Ontario since 1981
Last updated Feb 2021County Weed Species Herbicide Group Example Herbicide(s) Brant Lamb's-quarter Group 5 Aatrex, Sencor Brant Green pigweed Group 5 Aatrex, Sencor Brant Goosefoot Group 5 Aatrex, Sencor Brant Common ragweed Group 5 Aatrex, Sencor Brant Canada fleabane Group 9 glyphosate Brant Canada fleabane Group 2 Classic, FirstRate Bruce Waterhemp Group 2 Pursuit, Pinnacle Bruce Redroot pigweed Group 2 Pursuit, Classic Bruce Lamb's-quarter Group 5 Aatrex, Sencor Bruce Green pigweed Group 2 Pursuit, Classic Bruce Green pigweed Group 5 Aatrex, Sencor Bruce Eastern black nightshade Group 2 Pursuit Bruce Common ragweed Group 2 Pursuit, Classic Bruce Common ragweed Group 5 Aatrex, Sencor Bruce Canada fleabane Group 9 glyphosate Carleton Eastern black nightshade Group 2 Pursuit Carleton Common ragweed Group 2 Pursuit, Classic Chatham-Kent Waterhemp Group 9 glyphosate Chatham-Kent Redroot pigweed Group 2 Pursuit, Classic Chatham-Kent Redroot pigweed Group 5 Aatrex, Sencor Chatham-Kent Redroot pigweed Group 6 Basagran, Pardner Chatham-Kent Redroot pigweed Group 7 Lorox Chatham-Kent Large crabgrass Group 1 Assure II Chatham-Kent Lamb's-quarter Group 2 Pursuit, Pinnacle Chatham-Kent Lamb's-quarter Group 5 Aatrex, Sencor Chatham-Kent Green pigweed Group 2 Pursuit, Classic Chatham-Kent Green pigweed Group 6 Basagran, Pardner Chatham-Kent Green pigweed Group 5 Aatrex, Sencor Chatham-Kent Giant Ragweed Group 9 glyphosate Chatham-Kent Giant Ragweed Group 2 Pursuit, Classic Chatham-Kent Eastern black nightshade Group 22 Reglone, Gramoxone Chatham-Kent Common ragweed Group 2 Pursuit, Classic Chatham-Kent Canada fleabane Group 9 glyphosate Chatham-Kent Canada fleabane Group 2 Classic, FirstRate Dufferin Lamb's-quarter Group 5 Aatrex, Sencor Dufferin Green pigweed Group 5 Aatrex, Sencor Dufferin Canada fleabane Group 9 glyphosate Durham Lamb's-quarter Group 5 Aatrex, Sencor Durham Green pigweed Group 5 Aatrex, Sencor Durham Canada fleabane Group 9 glyphosate Elgin Redroot pigweed Group 2 Pursuit, Classic Elgin Lamb's-quarter Group 2 Pursuit, Pinnacle Elgin Lamb's-quarter Group 5 Aatrex, Sencor Elgin Green pigweed Group 2 Pursuit, Classic Elgin Green pigweed Group 5 Aatrex, Sencor Elgin Green pigweed Group 5 Aatrex, Sencor Elgin Giant foxtail Group 2 Accent, Pursuit Elgin Eastern black nightshade Group 2 Pursuit Elgin Common ragweed Group 2 Pursuit, Classic Elgin Canada fleabane Group 9 glyphosate Elgin Canada fleabane Group 2 Classic, FirstRate Essex Waterhemp Group 5 Aatrex, Sencor Essex Waterhemp Group 9 glyphosate Essex Waterhemp Group 2 Classic, Pinnacle, Pursuit Essex Waterhemp Group 14 Reflex, Blazer Essex Smooth pigweed Group 6 Basagran, Pardner Essex Redroot pigweed Group 2 Pursuit, Classic Essex Redroot pigweed Group 6 Basagran, Pardner Essex Lamb's-quarter Group 2 Pursuit, Pinnacle Essex Lamb's-quarter Group 5 Aatrex, Sencor Essex Green pigweed Group 2 Pursuit, Classic Essex Green pigweed Group 6 Basagran, Pardner Essex Green pigweed Group 5 Aatrex, Sencor Essex Giant Ragweed Group 9 glyphosate Essex Giant Ragweed Group 2 Pursuit, Classic Essex Giant foxtail Group 2 Accent, Pursuit Essex Field peppergrass Group 22 Reglone, Gramoxone Essex Common ragweed Group 2 Pursuit, Classic Essex Common ragweed Group 9 glyphosate Essex Common ragweed Group 5 Aatrex, Sencor Essex Canada fleabane Group 22 Reglone, Gramoxone Essex Canada fleabane Group 2 Classic, FirstRate Frontenac Lamb's-quarter Group 5 Aatrex, Sencor Frontenac Green pigweed Group 5 Aatrex, Sencor Frontenac Canada fleabane Group 9 glyphosate Frontenac Canada fleabane Group 2 Classic, FirstRate Grey Witchgrass Group 5 Aatrex, Sencor Grey Lamb's-quarter Group 5 Aatrex, Sencor Grey Green pigweed Group 5 Aatrex, Sencor Haldimand Witchgrass Group 5 Aatrex, Sencor Haldimand Redroot pigweed Group 2 Pursuit, Classic Haldimand Lamb's-quarter Group 5 Aatrex, Sencor Haldimand Green pigweed Group 2 Pursuit, Classic Haldimand Green pigweed Group 5 Aatrex, Sencor Haldimand Common ragweed Group 2 Pursuit, Classic Haldimand Common ragweed Group 5 Aatrex, Sencor Haldimand Canada fleabane Group 9 glyphosate Haldimand Canada fleabane Group 2 Classic, FirstRate Haliburton Lamb's-quarter Group 5 Aatrex, Sencor Haliburton Green pigweed Group 5 Aatrex, Sencor Halton Wild Carrot Group 4 dicamba, 2,4-D Halton Lamb's-quarter Group 5 Aatrex, Sencor Halton Green pigweed Group 5 Aatrex, Sencor Halton Canada fleabane Group 9 glyphosate Halton Canada fleabane Group 2 Classic, FirstRate Hamilton Redroot pigweed Group 2 Pursuit, Classic Hamilton Lamb's-quarter Group 5 Aatrex, Sencor Hamilton Green pigweed Group 2 Pursuit, Classic Hamilton Green pigweed Group 5 Aatrex, Sencor Hamilton Common ragweed Group 5 Aatrex, Sencor Hamilton Canada fleabane Group 9 glyphosate Hamilton Canada fleabane Group 2 Classic, FirstRate Hastings Lamb's-quarter Group 5 Aatrex, Sencor Hastings Canada fleabane Group 9 glyphosate Huron Redroot pigweed Group 2 Pursuit, Classic Huron Redroot pigweed Group 7 Lorox Huron Lamb's-quarter Group 5 Aatrex, Sencor Huron Green pigweed Group 2 Pursuit, Classic Huron Green pigweed Group 5 Aatrex, Sencor Huron Green pigweed Group 5 Aatrex, Sencor Huron Green foxtail Group 2 Accent, Pursuit Huron Eastern black nightshade Group 2 Pursuit Huron Common ragweed Group 2 Pursuit, Classic Huron Canada fleabane Group 9 glyphosate Huron Canada fleabane Group 2 Classic, FirstRate Kawartha Lakes Lamb's-quarter Group 5 Aatrex, Sencor Kawartha Lakes Green pigweed Group 5 Aatrex, Sencor Kawartha Lakes Green foxtail Group 2 Accent, Pursuit Lambton Waterhemp Group 5 Aatrex, Sencor Lambton Waterhemp Group 9 glyphosate Lambton Waterhemp Group 2 Classic, Pinnacle, Pursuit Lambton Waterhemp Group 14 Reflex, Blazer Lambton Redroot pigweed Group 2 Pursuit, Classic Lambton Lamb's-quarter Group 2 Pursuit, Pinnacle Lambton Lamb's-quarter Group 5 Aatrex, Sencor Lambton Green pigweed Group 2 Pursuit, Classic Lambton Green pigweed Group 5 Aatrex, Sencor Lambton Green foxtail Group 2 Accent, Pursuit Lambton Giant Ragweed Group 9 glyphosate Lambton Giant Ragweed Group 2 Pursuit, Classic Lambton Giant foxtail Group 2 Accent, Pursuit Lambton Common ragweed Group 2 Pursuit, Classic Lambton Cocklebur Group 2 Pursuit, Classic Lambton Canada fleabane Group 9 glyphosate Lambton Canada fleabane Group 2 Classic, FirstRate Lanark Lamb's-quarter Group 5 Aatrex, Sencor Lanark Green pigweed Group 5 Aatrex, Sencor Leeds and Grenville Witchgrass Group 5 Aatrex, Sencor Leeds and Grenville Lamb's-quarter Group 5 Aatrex, Sencor Leeds and Grenville Green pigweed Group 5 Aatrex, Sencor Lennox and Addington Redroot pigweed Group 2 Pursuit, Classic Lennox and Addington Lamb's-quarter Group 5 Aatrex, Sencor Lennox and Addington Green pigweed Group 2 Pursuit, Classic Lennox and Addington Green pigweed Group 5 Aatrex, Sencor Lennox and Addington Giant Ragweed Group 9 glyphosate Lennox and Addington Common ragweed Group 5 Aatrex, Sencor Lennox and Addington Canada fleabane Group 9 glyphosate Lennox and Addington Canada fleabane Group 2 Classic, FirstRate Middlesex Redroot pigweed Group 2 Pursuit, Classic Middlesex Redroot pigweed Group 7 Lorox Middlesex Lamb's-quarter Group 2 Pursuit, Pinnacle Middlesex Lamb's-quarter Group 5 Aatrex, Sencor Middlesex Green pigweed Group 2 Pursuit, Classic Middlesex Green pigweed Group 7 Lorox Middlesex Green pigweed Group 7 Linuron Middlesex Green pigweed Group 5 Aatrex, Sencor Middlesex Eastern black nightshade Group 2 Pursuit Middlesex Common ragweed Group 2 Pursuit, Classic Middlesex Canada fleabane Group 9 glyphosate Niagara Lamb's-quarter Group 5 Aatrex, Sencor Niagara Green pigweed Group 5 Aatrex, Sencor Niagara Green pigweed Group 5 Aatrex, Sencor Niagara Common ragweed Group 2 Pursuit, Classic Niagara Common ragweed Group 5 Aatrex, Sencor Niagara Canada fleabane Group 9 glyphosate Niagara Canada fleabane Group 2 Classic, FirstRate Norfolk Witchgrass Group 5 Aatrex, Sencor Norfolk Lamb's-quarter Group 5 Aatrex, Sencor Norfolk Common ragweed Group 5 Aatrex, Sencor Norfolk Common ragweed Group 5 Aatrex, Sencor Norfolk Common ragweed Group 2 Pursuit, Classic Norfolk Canada fleabane Group 9 glyphosate Norfolk Canada fleabane Group 2 Classic, FirstRate Northumberland Lamb's-quarter Group 5 Aatrex, Sencor Northumberland Green pigweed Group 5 Aatrex, Sencor Northumberland Canada fleabane Group 9 glyphosate Northumberland Canada fleabane Group 2 Classic, FirstRate Ottawa Lamb's-quarter Group 5 Aatrex, Sencor Ottawa Green pigweed Group 5 Aatrex, Sencor Ottawa Eastern black nightshade Group 2 Pursuit Ottawa Common ragweed Group 2 Pursuit, Classic Ottawa Canada fleabane Group 9 glyphosate Oxford Redroot pigweed Group 2 Pursuit, Classic Oxford Lamb's-quarter Group 5 Aatrex, Sencor Oxford Green pigweed Group 2 Pursuit, Classic Oxford Green pigweed Group 5 Aatrex, Sencor Oxford Green pigweed Group 5 Aatrex, Sencor Oxford Green foxtail Group 2 Accent, Pursuit Oxford Giant foxtail Group 2 Accent, Pursuit Oxford Eastern black nightshade Group 2 Pursuit Oxford Common ragweed Group 2 Pursuit, Classic Oxford Canada fleabane Group 9 glyphosate Oxford Canada fleabane Group 2 Classic, FirstRate Peel Lamb's-quarter Group 5 Aatrex, Sencor Peel Green pigweed Group 5 Aatrex, Sencor Peel Canada fleabane Group 9 glyphosate Peel Canada fleabane Group 2 Classic, FirstRate Perth Redroot pigweed Group 2 Pursuit, Classic Perth Lamb's-quarter Group 5 Aatrex, Sencor Perth Green pigweed Group 2 Pursuit, Classic Perth Green foxtail Group 2 Accent, Pursuit Perth Eastern black nightshade Group 2 Pursuit Perth Common ragweed Group 2 Pursuit, Classic Perth Canada fleabane Group 9 glyphosate Perth Canada fleabane Group 2 Classic, FirstRate Peterborough Lamb's-quarter Group 5 Aatrex, Sencor Peterborough Green pigweed Group 5 Aatrex, Sencor Peterborough Canada fleabane Group 9 glyphosate Peterborough Canada fleabane Group 2 Classic, FirstRate Prescott-Russell Witchgrass Group 5 Aatrex, Sencor Prescott-Russell Lamb's-quarter Group 5 Aatrex, Sencor Prescott-Russell Green pigweed Group 5 Aatrex, Sencor Prescott-Russell Common ragweed Group 2 Pursuit, Classic Prince Edward Lamb's-quarter Group 5 Aatrex, Sencor Prince Edward Canada fleabane Group 9 glyphosate Renfrew Lamb's-quarter Group 5 Aatrex, Sencor Simcoe Redroot pigweed Group 2 Pursuit, Classic Simcoe Redroot pigweed Group 5 Aatrex, Sencor Simcoe Redroot pigweed Group 7 Lorox Simcoe Lamb's-quarter Group 2 Pursuit, Pinnacle Simcoe Lamb's-quarter Group 5 Aatrex, Sencor Simcoe Green pigweed Group 2 Pursuit, Classic Simcoe Green pigweed Group 5 Aatrex, Sencor Simcoe Green pigweed Group 7 Lorox Simcoe Green pigweed Group 7 Linuron Simcoe Eastern black nightshade Group 2 Pursuit Simcoe Common ragweed Group 2 Pursuit, Classic Simcoe Canada fleabane Group 9 glyphosate Stormont, Dundas & Glengarry Wild mustard Group 5 Aatrex, Sencor Stormont, Dundas & Glengarry Redroot pigweed Group 2 Pursuit, Classic Stormont, Dundas & Glengarry Redroot pigweed Group 5 Aatrex, Sencor Stormont, Dundas & Glengarry Lamb's-quarter Group 2 Pursuit, Pinnacle Stormont, Dundas & Glengarry Lamb's-quarter Group 5 Aatrex, Sencor Stormont, Dundas & Glengarry Green pigweed Group 2 Pursuit, Classic Stormont, Dundas & Glengarry Green pigweed Group 5 Aatrex, Sencor Stormont, Dundas & Glengarry Eastern black nightshade Group 2 Pursuit Stormont, Dundas & Glengarry Common ragweed Group 2 Pursuit, Classic Stormont, Dundas & Glengarry Canada fleabane Group 9 glyphosate Stormont, Dundas & Glengarry Canada fleabane Group 2 Classic, FirstRate Victoria Green foxtail Group 2 Accent, Pursuit Waterloo Redroot pigweed Group 5 Aatrex, Sencor Waterloo Lamb's-quarter Group 5 Aatrex, Sencor Waterloo Green pigweed Group 5 Aatrex, Sencor Waterloo Canada fleabane Group 9 glyphosate Waterloo Canada fleabane Group 2 Classic, FirstRate Waterloo Barnyardgrass Group 5 Aatrex, Sencor Wellington Witchgrass Group 5 Aatrex, Sencor Wellington Redroot pigweed Group 2 Pursuit, Classic Wellington Lamb's-quarter Group 5 Aatrex, Sencor Wellington Green pigweed Group 2 Pursuit, Classic Wellington Green pigweed Group 5 Aatrex, Sencor Wellington Green foxtail Group 2 Accent, Pursuit Wellington Eastern black nightshade Group 2 Pursuit Wellington Common ragweed Group 2 Pursuit, Classic Wellington Common ragweed Group 5 Aatrex, Sencor Wellington Canada fleabane Group 9 glyphosate Wellington Canada fleabane Group 2 Classic, FirstRate York Yellow foxtail Group 5 Aatrex, Sencor York Lamb's-quarter Group 5 Aatrex, Sencor York Green pigweed Group 5 Aatrex, Sencor York Common groundsel Group 5 Aatrex, Sencor York Canada fleabane Group 9 glyphosate York Canada fleabane Group 2 Classic, FirstRate Chatham-Kent Waterhemp Group 2 Pursuit, Pinnacle, Classic Chatham-Kent Waterhemp Group 5 Aatrex, Sencor Chatham-Kent Waterhemp Group 14 Reflex, Blazer Huron Waterhemp Group 2 Pursuit, Pinnacle, Classic Huron Waterhemp Group 5 Aatrex, Sencor Huron Waterhemp Group 9 glyphosate Huron Waterhemp Group 14 Reflex, Blazer Haldimand Waterhemp Group 2 Pursuit, Pinnacle, Classic Haldimand Waterhemp Group 5 Aatrex, Sencor Haldimand Waterhemp Group 9 glyphosate Haldimand Waterhemp Group 14 Reflex, Blazer Middlesex Waterhemp Group 2 Pursuit, Pinnacle, Classic Middlesex Waterhemp Group 5 Aatrex, Sencor Middlesex Waterhemp Group 9 glyphosate Norfolk Waterhemp Group 2 Pursuit, Pinnacle, Classic Norfolk Waterhemp Group 9 glyphosate Norfolk Waterhemp Group 14 Reflex, Blazer Wellington Waterhemp Group 2 Pursuit, Pinnacle, Classic Wellington Waterhemp Group 9 glyphosate Wellington Waterhemp Group 14 Reflex, Blazer Brant Waterhemp Group 2 Pursuit, Pinnacle, Classic Brant Waterhemp Group 9 glyphosate Bruce Waterhemp Group 9 glyphosate Elgin Waterhemp Group 2 Pursuit, Pinnacle, Classic Elgin Waterhemp Group 9 glyphosate Northumberland Waterhemp Group 2 Pursuit, Pinnacle, Classic Northumberland Waterhemp Group 9 glyphosate Wentworth Waterhemp Group 2 Pursuit, Pinnacle, Classic Wentworth Waterhemp Group 9 glyphosate Essex Canada fleabane Group 9 glyphosate Wellington Wild Carrot Group 4 dicamba, 2,4-D Huron Large crabgrass Group 1 Assure II
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ONTARIO EXPERTISE IN HERBICIDE RESISTANCE
Academia (in alphabetical order):
Dr. François Tardif, University of Guelph (Main campus)
Dr. Peter Sikkema, University of Guelph (Ridgetown campus)
Extension (in alphabetical order):
Mike Cowbrough, OMAFRA Weed Specialist (Field Crops)
Kristen Obeid, OMAFRA Weed Specialist (Horticulture Crops)