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Managing Herbicide Resistant Weeds in Clearfield Wheat Systems

A recent article in Weed Technology by Drs. Rainbolt, Thill (Idaho), Yenish(WSU), and Ball (OSU) discusses the possibility of developing herbicide resistant weeds in a Clearfield system. They also published their findings in Extension bulletin PNW 572. The scientists used a computer model to demonstrate how agronomic practices and weed biology affect the rate of appearance of herbicide resistant downy brome, jointed goat grass, and wild oat in Pacific Northwest wheat-based cropping systems. The model also suggests herbicide rotation strategies for systems that include Clearfield wheat. Continuous use of Clearfield wheat and Beyond (imazamox) herbicide resulted in resistant downy brome in 5 years, resistant jointed goat grass in 7 years, and resistant wild oat in 10 years. The best strategy to prevent this is to reduce the soil seed bank with a Clearfield wheat-fallow rotation or rotations that contain non-group 2 (ALS inhibitor) herbicides (refer to PNW Bulletin 437, Herbicide-Resistant Weeds and Their Management for herbicide group numbers). However, the authors stress this is a computer simulation; results have not been tested in the field.

PNW 572, and PNW 437, are available in an easily printable format (pdf) at:


These publications are also available for purchase from the state extension publication offices: Idaho (208)885-7982; Oregon (541)737-2513; Washington (509)335-2857. Some shipping and handling fees and sales tax may apply.


Contact us: Hans Kok, (208)885-5971 | Accessibility | Copyright | Policies | WebStats | STEEP Acknowledgement
Hans Kok, WSU/UI Extension Conservation Tillage Specialist, UI Ag Science 231, PO Box 442339, Moscow, ID 83844 USA
Redesigned by Leila Styer, CAHE Computer Resource Unit; Maintained by Debbie Marsh, Dept. of Crop & Soil Sciences, WSU