Largest Eurasian Milfoil Control Project in PNW Continues to Yield Results

This view is representative of the conditions Aquatechnex biologists faced on the Pend Oreille System

This view is representative of the conditions Aquatechnex biologists faced on the Pend Oreille System

In 2006, the Idaho State Legislature recognized the threat Eurasian Milfoil posed to the water resources of the State.  Many of the larger lake systems in the Panhandle were heavily impacted by this invasive aquatic weed.  The Lake Pend Oreille and Pend Oreille River System were by far the most severely impacted system in the state.  The Bonner County Public Works Department’s Weed Superintendent moved to develop a program to take advantage of the funding that was made available by the State.

Aquatechnex biologists were selected to implement Eurasian Milfoil Management Program.  The team targeted over 4,000 acres of this noxious aquatic weed with four aquatic herbicide formulations.

Sonar Aquatic Herbicide was the backbone of this program.  Our team had successfully eradicated Eurasian Milfoil from a number of smaller lake systems by dosing the lake water volume at low levels and maintaining that dose for 6-8 weeks.  In a lake system as large as Pend Oreille the economics of that approach did not make sense.

We had also begun to work with a number of controlled release granular delivery systems SePRO scientists had developed to maintain the required lower exposure over time in a localized area of a large lake.  We designed a program that involved three treatments at two week intervals to target Eurasian Milfoil.

Each year since, our team has mapped the results of this major treatment as part of our ongoing work on the lake.  As of 2012, the vast majority of acreage treated remained milfoil free or showed very low levels of re-invading milfoil plants.  The initial cost of this treatment on a per acre basis was approximately $700.00.  Given the six seasons of invasive weed control delivered, the cost of delivering this control over time comes to $116.50 per acre per year.

This project is outlined in the attached Land and Water Magazine Article. MassiveEurasianlores

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