Assessing Benthic Barriers vs. Aggressive Cutting as Effective Yellow Flag Iris (Iris pseudacorus) Control Mechanisms

An experiment was initiated to study the effects of rubber benthic barriers vs. aggressive cutting on the invasive aquatic emergent plant, yellow flag iris. Treatments were compared against a control at two locations within British Columbia, Canada (Vaseux Lake and Dutch Lake). Yellow flag iris response was significantly different between the two sites, but biologically the results were identical: the benthic barrier killed yellow flag iris rhizomes within 70 d of treatment. Over the extent of the research, at Vaseux Lake the effect of aggressive cutting was no different from the control, while aggressive cutting was statistically no different than the benthic barrier at Dutch Lake. Vegetation regrowth approximately 200 d after the benthic barriers were removed was not detected at either location. These results indicate that rubber benthic barriers may be an effective treatment for yellow flag iris and maybe suitable for other, similar species. Nomenclature: Yellow flag iris, Iris pseudacorus L. IRPS. Management Implications: Rubber matting (benthic barriers) appeared to work well on the emergent aquatic invasive plant yellow flag iris. In less than 3 mo, rhizomes that were treated with the benthic barrier had very few living cells. Additionally, no regrowth from rhizomes was documented the following growing season, further indication of the successful effects of the barriers. Aggressive cutting is also used as a yellow flag iris treatment. Our research found that depending on the site, aggressive cutting may be no different than the untreated control; or it may be no different than the benthic barrier. More research is required to understand how environmental parameters may affect aggressive cutting of yellow flag iris. The abundant exposed soil following benthic barrier treatment, the presence of cattails, and the limited number of yellow flag iris germinants indicates that treated sites have a period of time posttreatment when restoration with desirable species could be implemented.