Curly Leaf Pondweed Treatment Update

Hayden Lake has been experiencing a new invasive aquatic weed Curly Leaf Pondweed on the north end near Sportsmans Access. This plant emerges and grows very fast in the spring, reaches the water surface and in midsummer and produces a turrion or reproductive structure that fuels the following years growth.

Unlike milfoil, there is only one EPA approved systemic aquatic herbicide that provides long term control of this weed. This herbicide has been applied three times to this area at three-week intervals starting in late April.

The mode of action of this product is extremely slow, from initial application to complete release and action of the residual herbicide can take 90 days or longer. Lake users should see a reduction in plant biomass in a few short weeks.

ISDA realizes that this biomass creates a short-term inconvenience, but the treatment results should be long lasting and continues to monitor the treatment efficacy.

Shoreline residents and water users will receive a public notification regarding a possible additional herbicide application.  The permit that governs this work requires that all shoreline residents within and a short distance from a treatment area be notified 14 days prior to applicaiton.  As a contengency, we are sending a notice that we may make a Diquat herbicide treatment after this 14 day period concludes and if there are still extensive beds of plants that have not yet fallen out of the water column.



Third and Last Sonar herbicide treatment to be performed Wednesday June 12th

Aquatechnex biologists will be performing the third Sonar herbicide treatment on Hayden Lake this coming Wednesday June 12th.  Affected areas will be posted with signage explaining the treatment and water use restrictions the previous day Tuesday June 11th.

We will also be evaluating the progress of this treatment, this herbicide is a very slow acting products.  It prevents the plant from making a pigment that is essential in protecting chlorophyll from being degraded by sunlight.  Generally it takes 8 weeks to start seeing plants falling out.

We will be collecting plants and shipping them to a laboratory that preforms effect analysis as well as making a visual inspection of all sites.

Start Up 2019, First Treatment for Hayden Lake

Aquatechnex is the contractor for the Idaho State Department of Agriculture (ISDA) for this spring treatment. The spring treatment is of Hayden Lake’s north end for two noxious weeds, Curly Leaf Pondweed and Eurasian Milfoil.

We will be using a product new to Hayden Lake’s treatment program this year. SonarONE Aquatic Herbicide has been selected to target early season growth. SonarONE is a slow release pellet formulation that will be applied three times to the treatment areas on the lake at about a three-week interval.

The herbicide SonarONE has the following EPA label restrictions:

  • no restriction on the use of the treated water for potable or domestic water supply,
  • no swimming restrictions, and
  • limited irrigation restrictions.

The irrigation restrictions depend on what you are irrigating. You may water established tree crops and established row crops/turf/plants seven days after each of the three applications. You may not water newly seeded crops/seedbeds or areas to be planted including over-seeded golf course greens until a water sample test indicates that levels are below 5 parts per billion. Water tests will be collected 2-3 weeks after each treatment interval, with results published on this website and on the ISDA invasive species website

While weather conditions may change the schedule, the proposed time line is as follows: the first treatment will be performed the week of April 22, the second treatment the week of May 13, and the last treatment the week of June 10. So please check back regularly.

Notifications for this treatment will be:

  • First sent via certified mail to all registered water rights holders within a quarter mile of the treatment area 2 weeks prior to the initial treatment.
  • Second, all residences along the shoreline within a quarter mile of the treatment area will receive a notice 2 weeks in advance of the treatment.
  • Third, public boat access and swimming areas will be posted 2 weeks prior to the initial treatment.
  • Lastly, all docks along the shoreline within a quarter mile of the treatment area, will be posted 24 hours in advance of each treatment.


A map of the treatment area can be viewed at this link  Sonar Herbicide Treatment Map