Hayden Lake Watershed Improvement District

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  • Living on Hayden Lake, Noxious Weeds, Recreation
  • April 24, 2019

What to Expect From the SonarOne / Fluridone Applications

Looking south one winter day from Rockaway Bay

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  • Living on Hayden Lake, Noxious Weeds, Recreation
  • April 24, 2019
AquaTechnex and the Idaho State Department of Agriculture (ISDA) are on the lake today, applying the first treatment of SonarOne in the North Arm.
Table of what to expect from Fluridone Treatments.

Over the next six-to-nine weeks, lake-watchers will see the Curlyleaf Pondweed in that part of Hayden Lake struggle to overcome the effects of the herbicide. It will even appear to grow, although the new growth will be sparse, stringy, and unhealthy-looking.  Map of Hayden Lake shows North Arm treatment area.Curlyleaf Pondweed is the first aquatic plant to emerge in the spring.Five to six weeks from now, the Curlyleaf will finally look like it’s dying. In nine weeks, we expect it to be gone. Any Eurasian Watermilfoil, which is early in its growth cycle, will die back such that ISDA anticipates few issues with it later in the season. The herbicide will affect the native species as well.

SonarOne, a Fluridone-containing herbicide is in the form of time-release pellets. If you were in the North Arm today, you might have seen the applicator spraying these across the top of the water. The pellets will sink to the lake bottom where they will slowly release the herbicide to maintain an effective concentration near the root-level of the plant.

Concentration is Key.

ISDA carefully selected the SonarOne application rate to arrive at a Fluridone concentration that will kill the Curlyleaf but will have the least impact on residents’ and visitors’ use of the water.   The desirable range is 5 to 20 parts per billion (ppb). If below 5 ppb, the herbicide might stress but not kill the plants; if above 20 ppb, drinking water restrictions would need to be imposed. The target is 12 ppb.

The application rate is somewhat higher along the shoreline and lower in the center of the North Arm.  This gradient will accommodate the way things move out there. In that dynamic system, the forces of wind, friction, and gravity move the water and all it contains toward the middle and northward along the arm. The variable application rate, working with the natural water exchange, should yield a uniform Fluridone concentration across the treatment area.

Exposure Time is Important Too.

Time is the other factor affecting the success of this treatment.  The plant absorbs Fluridone through its shoots and stems and transports the chemical throughout the plant system. In the plant cells, the Fluridone disrupts the plant’s ability to build new resources.  The plant continues to grow, using up the resources that it has in store. Provided it can’t out-grow the damage done by the herbicide, it dies. Thus, the lengthy exposure is the time that it takes the plant to use up its resources while it’s unable to produce new. A second and third application in the North Arm will maintain the herbicide concentration throughout the needed exposure time.

Minimal Water-Use Restrictions are in Place.

Even though ISDA designed the treatment plan to minimize water-use restrictions, there are a few that are worthy of attention.  According to the label, homeowners cannot use water from within the treatment area to irrigate established crops for the first seven days post-application.  After that, feel free to use lake water on your trees and yard only.  NEW plantings should not be irrigated with treated lake water until testing confirms that Fluridone levels are below 5 ppb. The label does not call for any swimming or potable/domestic water-use restrictions.

The first water-testing, called a FasTEST, will take place 2-and-a-half weeks from now. The results will reveal whether affected property owners can irrigate their seedlings with lake water for the half-week until the next herbicide application. It will also tell ISDA whether the system met their expectations for water movement and chemical concentration. ISDA and HLWID will post results within a day of testing.

Please provide feedback.

As always, ISDA welcomes your feedback. Please participate in our poll and share more feedback, questions, and thoughts in the comments below.

Are you a water-rights holder? Did you receive the notice via certified mail?
  • Add your own answer to the list by typing here.
Results
Do you live along the North Arm? Did you find the 14-day notice tacked to your door?
  • Add your own answer to the list by typing here.
Results
Did you see the notices posted at Honesuckle or Sportsman's boat launch?
  • Add your own answer to the list by typing here.
Results

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2 Responses

  1. Bob Kirkwood says:
    April 26, 2019 at 4:53 pm

    Got the certified letter. No sign on the “door” but no problem. There was a notice on our sign post off Hayden Lake drive which is OK since we have 6 “doors”. We also got a call from Jeremy V which was great. Much better notification this year. Question: this herbicide kills plants, there are watering restrictions although limited ones, but the water is drinkable? No potable water restrictions? Seems odd.

  2. Melissa Schroeder says:
    April 26, 2019 at 1:03 pm

    Thanks team for your efforts in tackling our weeds!
    We are in McCleans Bay where the weeds were thick and a nuisance for boating and swimming. We look forward to a beautiful weed free Lake to enjoy all summer.

Comments are closed.

Idaho Discovers Invasive Zebra Mussels in Aquarium Products

lake debris build-up in Mokins Bay, 2018

2021 Lake Debris Removal Sponsored by the Improvement District

Recreational Boating on Hayden Lake

Potential Ordinance Change Will Affect Narrow Waterways, Not Hayden Lake

Looking south one winter day from Rockaway Bay

Monthly Meeting Minutes Archive

A view from the dike at 2/2020 low water.

More to Explore In the Hayden Lake Watershed

Snow caps the mountains north of Hayden Lake late into April, '19.

Monthly Meetings

Looking south one winter day from Rockaway Bay

Monthly Meeting Minutes Archive

A view from the dike at 2/2020 low water.

More to Explore In the Hayden Lake Watershed

Snow caps the mountains north of Hayden Lake late into April, '19.

Monthly Meetings

  • Related Content: Living on Hayden Lake, Noxious Weeds, Recreation
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About HLWID

The mission of the Hayden Lake Watershed Improvement District is to protect and enhance the water quality and the environmental quality within the watershed.

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  • 2021 Community Meeting – Invasive Aquatic Weeds and More
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  • 2021 Lake Debris Removal Sponsored by the Improvement District
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  • Thank you, Pat Lund. Welcome new Board Member, Kristine Bartz

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Monday 4/16, 7:00 p.m.

HLWID Monthly Meeting

HLWID's Monthly Meetings will move to teleconferencing in order to ensure the health and safety of our constituents. For 4/16's meeting, dial 641-715-0861 and enter code 398963# at the prompt. This is a public meeting; all are welcome.