|WOOLF, THOMAS - Idaho State Department Of Agriculture|
|WERSAL, RYAN - Lonza Corporation|
Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2016
Publication Date: 1/1/2017
Citation: Madsen, J.D., Woolf, T.E., Wersal, R.M. 2017. Flowering rush control on drawn-down sediment: Mesocosm and field evaluations. Journal of Aquatic Plant Management. 55:42-45.
Interpretive Summary: Flowering rush is an invasive aquatic plant that is difficult to control. We evaluated chemical and non-chemical management techniques in both mesocosm tank studies and field studies. Mesocosm studies found that bare-ground treatments of fluridone and triclopyr reduced the rhizome biomass of flowering rush by 24 weeks after treatment. A study of field plots did not find any control techniques that successfully reduced rhizome biomass by 16 weeks after treatment, but data collected on the labor required for management found that herbicide treatments required 38 seconds per plot, compared to 12 to 30 minutes per plot for digging, hand removal, and benthic barrier installation.
Technical Abstract: Flowering rush (Butomus umbellatus L.) is an invasive aquatic plant found in lakes and reservoirs across the northern portion of the United States and southern Canada. Little has been published on field trials assessing the efficacy of management activities, whether using herbicides or non-chemical management techniques. While some success has been documented for submersed herbicide treatments, no published accounts of treatments on bareground areas resulting from operational reservoir drawdown are available. We tested seven chemicals [acetic acid (45 and 90 kg ae ha-1), aminopyralid (0.06 and 0.12 kg ae ha-1), flumioxazin (1.31 and 2.63 kg ai ha-1), fluridone (1.12 and 2.24 kg ai ha-1), imazamox (0.28 and 0.56 kg ae ha-1), imazapyr (0.84 and 1.68 kg ae ha-1), penoxsulam (0.05 and 0.10 kg ai ha-1), and triclopyr (3.36 and 6.73 kg ae ha-1)] for bareground treatments in a mesocosm trial. We also five chemicals [acetic acid2 (45 kg ae ha-1), fluridone5 (2.24 kg ai ha-1), imazamox6 (0.56 kg ai ha-1), imazapyr7 (1.68 kg ai ha-1), and triclopyr9 (6.73 kg ae ha-1)] along with hand pulling, digging, and benthic barrier in a replicated plot study on the Clark Fork river delta, Pend Oreille Lake, Idaho. Our goal was to find management techniques that would reduce belowground biomass. In the mesocosm study, fluridone and triclopyr treatments reduced belowground biomass by 24 weeks after treatment. In the field trial, no treatments reduced belowground biomass relative to untreated plots by 16 weeks after treatment. The lack of efficacy may be due to high statistical variability. Data was also collected on the time to implement management techniques. Herbicide treatments averaged 38 s per plot, while non-chemical techniques required 12 – 30 m per plot.