Canarygrass that is resistant to some of the ACCase inhibitors ( Poast, Select, Fusilade and generics) was found in the Imperial Valley, CA. about ten years ago. An increasing number of problems with these herbicides on this weed have been reported each year. Grass resistance to this mode of action is not uncommon in this country and worldwide. Wild oat, rye grass, brome grass and other grasses have been documented to have developed some levels of resistance. While many of the herbicides using this mode of action are used on broadleaf crops, some of the grass herbicides used in grain also use this mode of action to control canarygrass. These include Dakota, Discover, Achieve, Axial and others. It is necessary to use herbicides that use a different mode of action to help avoid resistance or limit it once it has occurred. The ACCase inhibitors are the most widely used herbicides for postemergence control of both annual and perennial grasses and this can be difficult. There are some other effective herbicides that use a different mode of action such as Osprey or Simplicity. Preemergence herbicides such as Prowl (pendimethalin) that control grasses can also be effective.

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To contact Barry Tickes go to: btickes@ag.arizona.edu.

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.