Herbicide resistance: dealing with a new weed problem

Non-Peer ReviewedIn recent years, resistance to commonly used herbicides has developed in several weed species in Saskatchewan. The first examples were weeds resistant to herbicides in the sulfonylurea family (e.g., Glean, Ally, and Amber) and included kochia and Russian thistle. Next came green foxtail (wild millet) resistant to dinitroaniline herbicides (e.g., Treflan, Rival, and Edge). In the past two years wild oat and green foxtail samples have been identified that are resistant to many of the newer post-emergence herbicides, including Hoe-Grass, Triumph Plus, Laser, Poast and Achieve. In all cases resistance has developed in individual fields after repeated use of the same herbicide or herbicides with the same mode of action. For some growers, the development of resistant weed biotypes significantly restricts the choice of herbicide available for their weed control program. Growers need to become aware of the modes of action of the different herbicides that are available to them, and to ensure that they use an appropriate rotation of herbicides so that resistance does not increase in their fields. In addition, the use of non-chemical weed control methods should be encouraged, so that growers avoid the repeated use of herbicides