Prospects for Disrupting Rhizome Apical Dominance Prior to Chemical Treatment of Phalaris arundinacea

Reed canarygrass (Phalaris arundinacea) is a widely distributed invasive species that dominates many natural areas and restoration sites. Cost-effective suppression and restoration strategies need to be developed for plant communities affected by this species. Pretreatments designed to disrupt rhizome apical dominance may augment herbicide performance by making reed canarygrass rhizomes more susceptible to herbicide applications. I tested whether coupling pretreatment disking or kinetin application to herbicide application would enhance chemical control relative to only solitary herbicide application. I also evaluated the relative performance of two grass-selective herbicides, sethoxydim and fluazifop. All treatments suppressed reed canarygrass and indirectly led to improvements in existing native species abundance compared to the untreated control. In terms of reed canarygrass suppression, non–reed canarygrass aboveground biomass, and species diversity (Shannon’s diversity), fluazifop performed as well as sethoxydim. Reed canarygrass biomass was consistently lower in plots where either disking or kinetin pretreatments were coupled with herbicide application than in plots receiving only herbicide treatment, though the degree of additional suppression varied with choice of herbicide. When sethoxydim was used for follow-up herbicide applications, disking reduced reed canarygrass biomass more than the kinetin pretreatment, but when fluazifop was used, kinetin pretreatments and disking were similar in their suppressive effect. Results of this study suggest that coupling these pretreatments with herbicide application can improve grassselective herbicide performance on reed canarygrass.