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Title: Interactions between the root pathogen Rhizoctonia solani AG-8 and acetolacetate synthase-inhibiting herbicides in barley

Author
item LEE, HYEJIN - Washington State University
item ULLRICH, STEVEN - Washington State University
item BURKE, IAN - Washington State University
item YENISH, JOSEPH - Washington State University
item Paulitz, Timothy

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2011
Publication Date: 2/3/2012
Citation: Lee, H., Ullrich, S.E., Burke, I.C., Yenish, J., Paulitz, T.C. 2012. Interactions between the root pathogen Rhizoctonia solani AG-8 and acetolacetate synthase-inhibiting herbicides in barley. Pest Management Science. 68(6):845-852.

Interpretive Summary: The widespread acceptance of reduced-tillage farming in cereal cropping systems in the Pacific Northwest (PNW) of the U.S. has resulted in increased use of herbicides for weed control. However, soil residual levels of widely used imidazalone herbicides limit the cultivation barley, which is more sensitive than wheat. In addition, increased severity of the root rot disease caused by Rhizoctonia solani is associated with reduction in tillage. Many crops exhibit altered disease responses after application of registered herbicides. In this study, the injury symptoms in barley caused by sublethal levels of two Group 2 herbicides, imazamox or propoxycarbazone-sodium were assessed in combination with the root rot pathogen, Rhizoctonia solani AG-8. Both herbicides and pathogen had negative impacts on plant growth parameters and interactions between pathogen and herbicide were detected. The results suggested sublethal levels of herbicides and R. solani could alter severity of injury symptoms, possibly due to the herbicide predisposing the plant to the pathogen.

Technical Abstract: The widespread acceptance of reduced-tillage farming in cereal cropping systems in the Pacific Northwest (PNW) of the U.S. has resulted in increased use of herbicides for weed control. However, soil residual levels of widely used imidazalone herbicides limit the cultivation barley, which is more sensitive than wheat. In addition, increased severity of the root rot disease caused by Rhizoctonia solani is associated with reduction in tillage. Many crops exhibit altered disease responses after application of registered herbicides. In this study, the injury symptoms in barley caused by sublethal levels of two Group 2 herbicides, imazamox or propoxycarbazone-sodium were assessed, in factorial combinations with a range of inoculum levels of the root rot pathogen, Rhizoctonia solani AG-8. Both herbicides and pathogen had negative impacts on plant growth parameters such as root and shoot dry weight, shoot height and 1st leaf length, and interactions between pathogen and herbicide were detected. The results suggested sublethal levels of herbicides and R. solani could alter severity of injury symptoms, possibly due to the herbicide predisposing the plant to the pathogen.