Herbicide Resistant Weed Testing Results
- by: Mike Cowbrough, OMAFRAFriday May 1st, 2009
Controlling six common annual species in Ontario fields just got tougher since the University of Guelph's Department of Plant Agriculture confirmed 43 herbicide resistant weed populations from the 2008 growing season. These testing results represent a 90% confirmation level of "suspected" herbicide resistant weed populations sent in by growers and agronomists. The tables below summarizes testing results and provides alternative herbicides that will be effective on these particular resistant weeds in non-GMO soybeans. To view alternative options for field corn and cereals, go to Ontario's herbicide selector at www.weedpro75.com
Table 1. Herbicide options for Non-GMO soybeans to control specific herbicide resistant broadleaf weed populations.
Broadleaf Weed
Resistant to:
Other Strategies (Timing)
Pigweed species
Herbicide Resistance: group 2
(i.e. Pinnacle, Pursuit)
1. Boundary (PRE); Reflex/Blazer (POST)
2. Frontier Max (PRE); Reflex/Blazer (POST)
3. Valtera (PRE); Reflex (POST)
Pigweed species
Herbicide Resistance: group 2 + 5
(i.e. Pinnacle, Sencor)
1. Dual II Magnum (PRE); Reflex/Blazer (POST)
2. Frontier Max (PRE); Reflex/Blazer (POST)
3. Valtera (PRE); Reflex (POST)
Common Ragweed
Herbicide Resistance: group 2
(i.e. FirstRate, Pursuit)
1. Boundary (PRE); Reflex/Blazer (POST)
2. Frontier Max (PRE); Reflex/Blazer (POST)
3. Lorox (PRE); Reflex (POST)
Common Ragweed
Herbicide Resistance: group 7
(i.e. Lorox)
1. Boundary (PRE); FirstRate (POST)
2. Cleansweep (POST)
3. Conquest (PRE)
4. Broadstrike Dual Magnum
Lamb's-quarter
Herbicide Resistance: group 2
(i.e. Pinnacle, Pursuit)
1. Boundary (PRE); Basagran (POST)
2. Valtera (PRE); Basagran (POST)
3. Frontier Max (PRE); Basagran (POST)
Lamb's-quarter
Herbicide Resistance: group 5
(i.e. Sencor)
1. Pinnacle (POST)
2. Cleansweep (POST)
3. Valtera (PRE)
Lamb's-quarter
Herbicide Resistance: group 2 + 5
(i.e. Pinnacle, Pursuit, Sencor)
1. Valtera (PRE); Basagran (POST)
Eastern Black Nightshade
Herbicide Resistance: group 2
(i.e. Pursuit)
1. Valtera (PRE)
2. Boundary (PRE); Reflex/Blazer (POST)
3. Frontier (PRE); Reflex/Blazer (POST)
4. Lorox L (PRE); Reflex/Blazer (POST)
Table 2. Herbicide options for Non-GMO soybeans to control specific herbicide resistant grassy weed populations.
Grassy Weed
Resistant to:
Other Strategies (Timing)
Green Foxtail
Herbicide Resistance: group 2
(i.e. Pursuit)
1. Dual II Magnum (PRE)
2. Frontier Max (PRE)
3. Assure II (POST)
4. Poast Ultra (POST
5. Excel Super (POST)
6. Select (POST)
Giant Foxtail
Herbicide Resistance: group 2
(i.e. Pursuit)
1. Dual II Magnum (PRE)
2. Frontier Max (PRE)
3. Assure II (POST)
4. Poast Ultra (POST
5. Excel Super (POST)
6. Select (POST)
For more information on herbicide resistant weeds in Ontario visit:
www.plant.uoguelph.ca/resistant-weeds
Special thanks go to: Dr. Francois Tardif, Peter Smith and Dr. Peter Sikkema, University of Guelph
Associated Weeds: | Eastern black nightshade | Giant foxtail | Green foxtail | Lamb's-quarters | Pigweed, Green | Pigweed, Redroot | Ragweed, common |