Following large-scale herbicide spraying and burning on Assateague Island, a barrier bar island located in Maryland and Virginia, the invasive common reed (Phragmites australis) was largely reduced from vast monocultures to less dense patches interspersed within maritime shrublands. To improve the control of these remnant/reemerging infestations and limit further nontarget damage, we tested three new treatments: mechanical cutting followed by dripping imazapyr onto stems, cutting followed 2 wk later by the foliar spraying of regrowth, and simple cutting with and without the removal of Phragmites litter. All herbicide treatments and cutting paired with litter removal significantly reduced Phragmites coverage (P ≤ 0.01) when compared with untreated controls. Native plant coverage was significantly greater after the cut-stem treatment than after traditional foliar spraying (P ≤ 0.01) because of the former's reduced herbicide use and more direct contact limited to Phragmites stems; native coverage was also greater after litter removal than when litter remained (P ≤ 0.001). Cutting followed by stem applications of herbicide is an effective means of treating scattered common reed stands in sensitive habitats, and litter removal after cutting can provide native vegetation with an advantage at recolonization.
Nomenclature: Imazapyr, common reed, Phragmites australis (Cav.) Trin. ex Steud.
Management Implications: Common reed (Phragmites) infestations that are interspersed throughout a shrubland of native vegetation pose a unique set of challenges. The most widespread methods for treating Phragmites involve the aerial and ground spraying of herbicide, mechanical clearing, and prescribed fire, all of which are impractical and extremely destructive to nontarget vegetation in this environment. Cutting Phragmites with a brush cutter, hand clippers, or both tools, and dripping imazapyr directly onto 5 to 25% of cut stems greatly limits the damage to nontarget vegetation relative to foliar spraying of herbicide and is equally effective at reducing Phragmites cover. Cutting followed by foliar spraying of Phragmites regrowth is as effective as treating 50% of cut stems with herbicide both in reducing Phragmites cover and limiting nontarget species damage. When accompanied by litter removal, cutting can significantly reduce Phragmites cover and greatly improve native plant regeneration in areas where herbicide cannot be applied, such as near open water or within sensitive areas containing rare or federally listed plant species. Cutting followed by stem-spraying generally requires less herbicide relative to the other methods tested, even in spite of this treatment's higher requisite herbicide concentration. The two alternative methods of applying herbicide tested herein require the same or slightly more person-hours to implement (relative to foliar-spraying of established stands), but they have an enhanced efficacy and utilize less herbicide.