Efficacy of Imazapyr and Glyphosate in the Control of Non‐Native Phragmites australis

Abstract

The cosmopolitan common reed (Phragmites australis) has been expanding into previously unoccupied wetland habitats throughout North America. This invasion by a non-native haplotype of Phragmites has become a major concern due to a reduction in plant diversity, reduction of faunal biodiversity, and changes in ecosystem structure. A randomized complete block design was used to compare the efficacy of two herbicides, glyphosate (Rodeo, Dow AgroSciences, IN, U.S.A.) and imazapyr (Habitat, BASF Corporation, NC, U.S.A.), on 1-ha Phragmites monoculture in a shallow borrow pit. Six foliar experimental treatments were applied consisting of (1) 2% glyphosate formulation, June application; (2) 2% glyphosate formulation, September application; (3) 2% imazapyr formulation, June application; (4) 2% imazapyr formulation, September application; (5) 5% imazapyr formulation, June application; and (6) 5% imazapyr, September application. Experimental plots were monitored yearly for two years after treatment. Relative importance values (RIV) were determined to assess the efficacy of herbicide treatments. We report that imazapyr foliar application is statistically superior to glyphosate in reducing Phragmites RIV, with no significant differences between the 2 and 5% formulations. Both herbicides are more effective in reducing Phragmites RIV if applied early in the growing season (June). No significant differences in non-Phragmites plant recolonization were observed between herbicide treatments over the two-year time course. These results suggest that imazapyr is superior in reducing Phragmites RIV, and that earlier applications of herbicides may be more effective on Phragmites. However, managers must note that adjacent nontarget plant species may be negatively affected by earlier treatments.

Invasive Phragmites australis management outcomes and native plant recovery are context dependent

“…This finding supports herbicide label recommendations for application in the fall, when absorbed herbicides can be translocated along with the carbohydrates Phragmites sends to rhizomes in preparation for senescence (Tu et al, ). Also, we found no significant advantage to imazapyr over glyphosate using summer applications in contrast to Derr () and Mozdzer et al (). Thus, the benefits of imazapyr may not justify its increased cost.…”

“…We addressed these questions: First, what are effective treatments for reducing Phragmites cover? We expected that our results would mirror other studies—imazapyr applications would be superior to glyphosate, and summer applications would be superior to fall applications (Derr, ; Mozdzer et al, ). Second, which treatments limit Phragmites seed production?…”

“…Managers have expressed uncertainties about the most effective type of herbicide, as well as the best timing of herbicide application for both Phragmites removal and native plant recovery (Rohal, Kettenring, Sims, Hazelton, & Ma, ). Imazapyr was more effective than glyphosate at Phragmites removal in some studies (Derr, ; Mozdzer, Hutto, Clarke, & Field, ), but there are questions about its long‐term impact on native plant recovery due to its persistence (up to 4 years) in the soil, and ability to be adsorbed by plant roots (Hazelton et al, ; Tu, Hurd, & Randall, ). Summer applications of herbicide were equally, if not more, effective than fall applications at Phragmites removal in short‐term management studies with limited monitoring (e.g., 1–2 growing seasons of treatment with post‐treatment monitoring in year of or just 1 year post‐application; Derr, ; Mozdzer et al, ).…”

Long-term monitoring of an invasion process: the case of an isolated small wetland on a Mediterranean Island, second stage: toward a complete restoration

“…Although the technical and scientific literature contains a number of cases of successful control/eradication of cattails and common reed by emplying these products (Messersmith et al 1992;Mozdzer et al 2008), they might also have undesirable effects on nontarget species (Marrs et al 1989;Gardner & Grue 1996) and a number of groups of animal, such as amphibian species results particularly vulnerable (Mann & Bidwell 1999;Relyea 2005). In addition to plant species of conservation interest, a large population of the Tyrrhenian tree frog (Hyla sarda) is also here present.…”

Application of a glyphosate-based herbicide to Phragmites australis: Impact on groundwater and near-shore lake water at a beach on Georgian Bay

“…The most effective method of eradicating Phragmites is through a spray application of herbicide that contains the active ingredient glyphosate, such as Roundup® or Rodeo® (Ailstock et al, 2001;Kay, 1995;LHCCC, 2007;Mal and Narine, 2004;Marks et al, 1994;Mozdzer et al, 2005;OMNR, 2011;Riemer, 1976). The application of herbicide is most effective during the late fall when the plant is translocating its sugars from its leaves and stems to its roots.…”