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


Eurasian Milfoil Treatment Scheduled for Tomorrow Cancelled.

The treatment for Eurasian Watermilfoil (EWM) that was scheduled for tomorrow, Thursday August 16th has been cancelled.  Pre Treatment evaluation of the sites today found that the treatment that occurred July 25th had results making this treatment unnecessary as no viable EWM was present.

This means that there will be no water use restrictions for drinking, irrigation or swimming as no herbicide will be applied.

As many of you were notified about this treatment and impending restrictions, we are also going to post signage on your docks indicating that the treatment has been cancelled, this will happen this afternoon.

If you have any questions, please contact ISDA Noxious Weed Program at 208-332-8667.

Next Treatment Scheduled

The next treatment on Hayden Lake will be performed the week of August 13th with the probable day of Thursday August 16 weather permitting.  The treatment of the north end of the lake had to be split into two applications to insure good dissolved oxygen levels and comply with the herbicide label.

This treatment will be applied to the area in the center of this zone, the shoreline areas were treated last week.  The map can be viewed at Treatment Map

The green areas on this map were treated last week and water use restrictions have expired.  The Red area on this map is the area subject to this application.

Hayden Treatments Completed for the Week, note change in water use restrictions

The shoreline “search and control” mission for Eurasian Milfoil was completed on Wednesday of this past week.  Initially the entire shoreline was mapped as potential treatment area, direction from the State was to target infestations along the shoreline out to 20 feet that were “topped out”.  As posting started for this work on Tuesday, the team noted large areas were devoid of Eurasian Milfoil.  The treatment was modified to a “spot treatment” in most areas and that changes the water use restrictions from three days to one day within those treatment zones, and no water use restrictions outside of the treatment areas.

The major treatment in the north end of the lake near Sportsman’s was completed on Thursday.  This 270 acre treatment plot had to be broken into two application to comply with the label, “when treated large areas split the application into two treatments at 14 day intervals to insure adequate dissolved oxygen levels”.  As such, this treatment focused on the shorelines of the lake to well off shore.  The second half of this treatment will be performed the week of August 6th, with a target date of Thursday that week.  This treatment will be well off shore and away from any water intakes, there will be no water use restrictions imposed on shoreline residents from this treatment and no need to post the shoreline.

Hayden Lake Second Treatment

The second treatment of Eurasian Milfoil on Hayden Lake will be performed this coming week, July 23-27.  The treatment map can be viewed at this link, Treatment Map Week of July 23rd

You will note two treatment objectives.

The first treatment performed will be scheduled for Wednesday July 25th with signs posted 24 hours prior to application on your shoreline.  This treatment area is a “seek and destroy” type of treatment in an area 20 feet from the shoreline to the shore.  Only visible “topped out” milfoil will be treated within the shoreline area (yellow band on the map) by water craft equipped with hand held spray systems.

The second treatment will be in the north arm of the lake near Sportsman’s Boat Launch will be a two part treatment with the first treatment occurring on Thursday July 26th and Friday July 27th if necessary.  We will be treating the shoreline areas within this polygon this week.  This application will be made with boats equipped with hand gun systems for areas around docks and boats and submerged injection drop hoses for those areas further off shore.

The water use restrictions from the treatment areas are: do not use water from the treatment area for potable water use or irrigation for 3 days post treatment.  There are no swimming restrictions, but we recommend staying out of the water for 12 hours to let the herbicide distribute.

We will be leaving the middle part of the lake in North Arm/Sportsman’s Bay zone until 14 days later.  This is to be compliant with Littora Herbicide Label (EPA registration number 67690-53) and the aquatic application requirements.  This second application will not impose water use restrictions on any of the shoreline areas.  

First Hayden Lake Treatment Completed, Second Round On Deck Week of July 23rd

Aquatechnex has completed the first treatment under the Idaho Department of Agriculture’s Eurasian Milfoil Control Program on Hayden Lake.  This treatment focused on bays and shorelines on the East shoreline.

A second round of treatments are planned for the week of July 23rd,  this treatment will focus on the near shore areas around the perimeter of the lake.  Maps will be posted prior to treatment.