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Prospects for Disrupting Rhizome Apical Dominance Prior to Chemical Treatment of Phalaris Arundinacea Craig A

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Prospects for Disrupting Rhizome Apical Dominance Prior to Chemical Treatment of Phalaris Arundinacea Craig A RESEARCH REPORT Prospects for Disrupting Rhizome Apical Dominance Prior to Chemical Treatment of Phalaris arundinacea Craig A. Annen ABSTRACT 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 com- pared 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 suppres- sive effect. Results of this study suggest that coupling these pretreatments with herbicide application can improve grass- selective herbicide performance on reed canarygrass. Keywords: apical dominance, fluazifop, kinetin,UW Press reed canarygrass / Ecological (Phalaris Restorationarundinacea), sethoxydim eed canarygrass (Phalaris arun- 11 different plant community types bank and/or rhizome bud bank (Reyes Rdinacea) is a widely distributed (Curtis 1959). Reed canarygrass inva- 2004, Annen 2008). For this reason, perennial grass that invades and sions displace native plant species and I propose adopting the term “sup- dominates natural areas and restora- alter restoration trajectories and vege- pression” rather than “control” when tion sites that have been disturbed tation succession patterns (Apfelbaum discussing herbicide effects on reed by sedimentation (Werner and Zedler and Sams 1987, Maurer et al. 2003, canarygrass to take into account the 2002), nutrient enrichment (Wetzel Annen et al. 2008). Long-term, sus- fact that these effects often do not and van der Valk 1998, Green and tained control of this species continues persist beyond one or two growing Galatowitsch 2001), hydrological to be a difficult management objec- seasons (and also to prevent confu- instability or modification (Galatow- tive to achieve, particularly at sites sion when the term “control” is used itsch et al. 2000, Bonilla-Warford and where the disturbances that contribute in experimental design terminology). Zedler 2002, Miller and Zedler 2003), to reed canarygrass invasions cannot Post-application regrowth in reed or any combination of these factors be remedied prior to implementing canarygrass has been documented in (Kercher and Zedler 2004). !is inva- control programs. several herbicide studies (Preuninger sive species covers more than 202,000 Herbicide application, alone or in and Umbanhowar 1994, Kilbride and ha of Wisconsin, USA (Bernthal and combination with other treatments, Paveglio 1999, Rachich and Reader Hatch 2008), where it has fidelity for is the method most commonly 1999, Reinhardt and Galatowitsch employed for reed canarygrass control. 2004, Lesica and Martin 2004, Wilcox Ecological Restoration Vol. 28, No. 3, 2010 Herbicide applications are effective 2004, Annen et al. 2005, Hovick and ISSN 1522-4740 E-ISSN 1543-4079 in the short term, but repeated treat- Reinartz 2007, Wilcox et al. 2007, ©2010 by the Board of Regents of the ments are usually required because Annen 2008), and a mechanism to University of Wisconsin System. this species can resprout from its seed explain resprouting from rhizomes was September 2010 ECOLOGICAL RESTORATION 28:3 ! 291 4-ER28.3 Annen (291-99).indd 291 6/18/10 5:35 AM Figure 1. The effects of apical dominance and pretreatments on the distribution of herbicide within a perennial grass rhizome. When apical dominance is active, lateral buds are unaffected by herbicide and will develop into new tillers that will perpetuate the clone unless retreated with additional herbicide applications. When apical dominance is disrupted prior to herbicide application, herbicides are more uniformly distributed throughout the rhizome/tiller system, resulting in enhanced suppression and reduced regrowth. Herbicide application only (apical dominance in place) Quiescent lateral buds Active apical bud Unaffected lateral buds Carbohydrate and herbicide distributions are polarized within the rhizome Regrowth of new tillers Disking (apical dominance disrupted) Disking slices rhizomes into isolated fragments Ɣ Herbicide molecule Bud-bearing rhizome fragments resprout into new tillers and follow up herbicide application affects more of the clone Direction of herbicide translocation Kinetin pretreatment (apical dominance disrupted) Reduced regrowth Carbohydrate and herbicide distributions are uniform within the rhizome Figure 1. The effects of apical dominance and pretreatments on the distribution of herbicide within a perennial grass rhizome. When apical dominance is active, lateral buds are unaffected by herbicide and will develop into new tillers that will perpetuate the clone unless retreated with additional herbicide applications. When apical dominance is disrupted prior to herbicide application, herbicides are more uniformly distributed throughout the rhizome/tiller system, resulting in enhanced suppression and reduced regrowth. postulated by Annen (2008). Herbi- UWreed Presscanarygrass / Ecological rhizomes Restorationmore sus- reed canarygrass clones. Apical domi- cide performance depends on several ceptible to the effects of herbicides nance gives rise to rhizome buds that factors, including choice of herbicide, (Hillman 1985, Harker and Vanden are physiologically, anatomically, and proper use of additives, and appli- Born 1997, Annen 2004). Coupling morphologically heterogeneous (Hill- cation timing, and further depends accessory treatments (such as tillage man 1985, Sachs 2002). As a result on how an herbicide is used in the or growth regulator pretreatment) of apical dominance, perennial grass context of the life history traits of the with herbicide application has been rhizomes possess two types of buds: target species. Life history traits such shown to improve reed canarygrass actively growing apical buds that give as perenniality and clonal expansion, suppression and reduce the magnitude rise to new tillers, and metabolically both of which are conferred by rhizome of regrowth in several recent studies inactive (dormant) lateral buds that systems, complicate control efforts. In (Kilbride and Paveglio 1999, Paveglio initiate renewed growth whenever a order to completely kill a perennial and Kilbride 2000, Hovick and Rein- disturbance affects top growth or the species such as reed canarygrass, foliar- artz 2007, Annen 2008). rhizome apex. !ese dormant lateral applied herbicides need to be translo- rhizome buds may contribute substan- cated to rhizomes in toxic quantities Rhizome Apical tially to reed canarygrass resurgence and must also be distributed through- Dominance and Reed capacity: Reyes (2004) measured an out the entire rhizome system. Regret- average of 820–900 dormant rhizome Canarygrass Control tably, systemic herbicides tend to con- buds per square meter (47%–76% of centrate only in the distal, actively Apical dominance is the inhibitory the total buds) in a well-established growing portions of perennial grass influence of the rhizome apex on lat- reed canarygrass stand. rhizomes because of apical dominance eral rhizome bud outgrowth and rhi- Apical dominance causes carbo- (Harker and Dekker 1988). Acces- zome branching. Holt (1954), Mar- hydrates and inorganic nutrients to sory treatments that disrupt rhizome quis and others (1979), and Reyes concentrate at the rhizome apex rather apical dominance and stimulate lateral (2004) presented evidence that an being uniformly distributed through- rhizome bud outgrowth may make apical dominance system operates in out the entire rhizome (Figure 1). 292 ! September 2010 ECOLOGICAL RESTORATION 28:3 4-ER28.3 Annen (291-99).indd 292 6/18/10 5:35 AM Herbicides applied to aboveground sites with remnant sod and no prior Evaluating Fluazifop as an leaves and culms likewise accumulate history of tillage), no-till methods that Alternative to Sethoxydim in rhizome apices because they are can elicit similar effects on rhizome transported along with the carbohy- suppression (such as plant growth Sethoxydim and fluazifop are two drate assimilate stream. Harker and regulator applications) are potential postemergence systemic graminicides Dekker (1988) measured the distal/ pretreatment options, but further with the same mode of action (non- basal accumulation ratio (a measure research is required before protocols competitive inhibition of lipid synthe- of the degree of uniformity of her- can be established for their use. Harker sis) but from different
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