Herbicide mixtures are more effective than rotations in slowing the evolution of herbicide resistance, according to a new report in Weed Technology.
Herbicide rotation is now the most common form of herbicide-resistance management practice among farmers in Canada. Although herbicide mixture is common, there are obstacles to it becoming as common as rotation. The authors of this report conducted a 4-year study to determine which method more readily slows herbicide-resistance evolution.
From 2004 to 2007, two sites of field pennycress co-occurring with wheat in Saskatchewan were treated with an acetolactate synthase (ALS) inhibitor and bromoxynil/MCPA. Treatments consisted of either a mixture of the two compounds or a rotation of them.
For the rotation treatment, the level of resistance of recruited seedlings had increased from 29% to 85% by the end of 4 years. For the mixture treatment, the level of resistance by the end of 4 years was similar to that of the nontreated control.
As a result of the study, the researchers say the herbicide industry needs to research and develop a broader range of herbicide mixtures to support what farmer surveys and modeling simulations already indicate: mixtures are the superior method for slowing evolution of resistance to herbicides.
Click here to read the entire study, Selecting for Weed Resistance: Herbicide Rotation and Mixture (Vol. 23(3):363-370, 2009).