ARS | Publication request: SELECTIVE CONTROL OF JOINTED GOATGRASS WITH IMAZAMOX IN HERBICIDE RESISTANTWHEAT

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 17, 1998
Publication Date: N/A

Interpretive Summary: In the western United States, jointed goatgrass is a winter annual grass weed that infests winter wheat-producing areas. It is an economic problem because it reduces wheat yield and land value, increases dockage penalties, and forces growers to produce spring crops which are not as profitable as winter wheat. Jointed goatgrass can not be controlled selectively in wheat. A possible approach to managing jointed goatgrass is by the development of a herbicide resistant winter wheat variety that is resistant to several times the normal use rate of a graminicide. Recently an imidazolinone-resistant (IR) wheat variety was released for field testing the selective control of jointed goatgrass and injury of the crop. For 2 years at two locations in the Pacific Northwest (PNW) imazamox applied to winter wheat effectively controlled jointed goatgrass, greatly reduced the dockage penalty for contaminated grain, increased grain yield, and did not severely injure wheat. This new strategy will expand growers' options for managing jointed goatgrass. However, they need to be cautious. The use of herbicide resistant crops is only another tool for weed management and growers must integrate this strategy into their best management practices already utilized on their farms.

Technical Abstract: Jointed goatgrass (JGG) is a serious problem for winter wheat producers throughout the western U.S. Interference from this weed can severely reduce grain yield and contaminate harvested grain resulting in dockage losses. There are currently no selective herbicides for control of JGG in wheat. Management of JGG requires rotating to spring-seeded crops or maintenance of extensive fallow periods so that infested fields remain out of winter cereal production for three to five years. In most parts of the dryland Pacific Northwest (PNW), this has proven to be an unprofitable option. An imidazolinone-resistant (IR) wheat mutant in the winter wheat variety 'Fidel' has been identified, characterized, and seed increased for field testing. 'Fidel' is classed as hard red wheat. The objectives of this research were to evaluate imazamox, (AC299,263) an imidazolinone herbicide, for selective control of JGG in IR 'Fidel' wheat and assess injury to winter wheat under PNW dryland environments.