Introduction

50
Table 10. Herbicide-Resistant Weeds in Western Canada, continued
Weed Herbicide Group Locations Confirmed
Lamb’s-quarters Group 2 SK
Group 5
Occurs in Ontario
False ragweed (Marshelder) Group 2 Occurs in North Dakota
Mustard, Ball Group 2 AB
Mustard, Wild Group 2 AB, MB, SK
Group 4
MB
Group 5
MB
Narrow-leaved hawk's-beard Group 2 AB
Persian Darnel Group 1 AB, SK
Redroot pigweed Group 2 MB, SK
Group 5
Occurs in Ontario
Russian thistle Group 2 AB, SK
Group 9
Occurs in Montana
Shepherd’s-purse Group 2 AB, SK
Smartweed, pale Group 2 MB
Spiny Annual Sow-thistle Group 2 AB, MB
Stinkweed Group 2 AB, MB, SK
Waterhemp Group 2 & Group 9 Occurs in North Dakota
Wild buckwheat Group 2 AB
Wild oat Group 1 AB, MB, SK
Group 2
AB, MB, SK
Group 8
AB, MB, SK
Multiple combinations of:
Groups 1 & 2,
Groups 1 & 8,
Groups 2 & 8,
Groups 1, 2 & 8,
Groups 1, 2, 8, 15 (MB)
AB, MB, SK
See Table 8 on page 44 for a complete list of products in each Herbicide Resistance Group.
If Weed Resistance Develops on Your Farm
It is important to identify weed resistance before it spreads across your farm. Plan on conducting a “patch watch” scouting
program this summer to identify suspicious patches before they become difficult to manage. Resistant weed patches have
been identified on fields where producers were unaware of their existence.
Your patch watch program should begin shortly after spraying and continue through July after the crop has headed out
and most weeds are visible from a distance. If you find suspicious looking patches, contact your local agricultural office or
crop protection company representative to assist you in confirming weed resistance. If resistance is suspected:
1. Map the location of the patches and mark them with stakes so you will remember their location.
2. Mow, cultivate or spot spray the patches. Resistant patches should not be allowed to produce seed.
3. Patchy areas should NOT be harvested with the rest of the field. Harvest these areas separately, and make sure
to clean all harvesting equipment before leaving the area to prevent the spread of seeds across the field or to a
neighbouring field.
4. Check patches each year to monitor their spread. Keeping your resistant weeds isolated to a manageable patch is
easier than dealing with an entire field of resistant weeds.