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|Title:||Field evaluation of Triclopyr (Garlon 3A) for controlling Eurasian watermilfoil in the Pend Oreille River, Washington|
United States. Army. Corps of Engineers. Seattle District.
Aquatic Plant Control Research Program (U.S.)
Getsinger, Kurt D.
Madsen, John Douglas.
Netherland, Michael D.
|Keywords:||Aquatic plant control|
Pend Oreille River
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: In an effort to evaluate the selective control of the exotic weed Eurasian watermilfoil (Myriophyllum spicatum L.) and to assess the recovery of the native submersed plant community, a 6-ha river and 4-ha cove plot were treated with the herbicide triclopyr at application rates of 2.5 and 1.75 mg/𝓁. respectively, in the Pend Oreille River, Washington, in August 1991. Water-exchange half-lives within the plots were measured using rhodamine WT dye and triclopyr dissipation rates were also calculated. Triclopyr concentrations were below proposed potable water tolerance levels (0.5 mg/𝓁) within the river treatment plot by 3 days after treatment (DAT), and 675 m downstream of that plot by 1 DAT. Following the cove treatment, triclopyr residues ranged from 0.12 to 0.29 mg/𝓁 by 7 DAT, and from <0.01 to 0.06 mg/𝓁 as close as 150 m downstream from the plot. Eurasian watermilfoil biomass was reduced by 99 percent in the treated plots at 4 weeks posttreatment, remained low 1 year later (river treatment, 28 percent of pretreat levels; cove treatment, 1 percent of pretreat levels), and was still at acceptable levels of control at 2 years posttreatment (river treatment, 47 percent of pretreat levels; cove treatment 24 percent of pretreat levels). The 4-week posttreatment efficacy results verified triclopyr concentration/exposure time relationships for controlling Eurasian watermilfoil developed under laboratory conditions. Nontarget native plant biomass increased 500 to 1,000 percent by 1 year posttreatment, and remained significantly higher in the cove plot at 2 years after treatment. Native species diversity doubled following herbicide treatment, and this robust commuruty delayed the reestablishment and dominance of Eurasian watermilfoil for three growing seasons.
|Appears in Collections:||Technical Report|