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:
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.