June/July ’24 Weed Survey Results

An Idaho State Department of Agriculture (ISDA) crew collected 1,773 individual survey points throughout Hayden Lake in search of Eurasian Watermilfoil (EWM). As scheduled, they completed this comprehensive survey at the end of June. 

Most survey points were free of EWM. However, driven by ISDA’s Noxious Weed Control strategy, every site that did yield active, growing EWM is marked for treatment.

Treatments to Remove Active EWM: Diver-assisted (TBD) or Chemical (July 22-24)

Single-plant to very small incursions (i.e., less than 25% of the target species) will be mechanically removed by diver-assisted means. The dates for these diver removal efforts are yet to be determined. Look for the green dots or polygons on ISDA’s 2024 Annual Treatment Map. 

ISDA, through a hired applicator, will apply ProcellaCOR®, an aquatic herbicide, to the areas with larger EWM infestations (more than 25% of the target species) between July 22nd and 24th. The 2024 Annual Treatment Map marks these locations with yellow dots or polygons.

PROCELLACOR® Herbicide Restrictions

As directed by the ProcellaCor label, water-use restrictions are minimal:

• There are no drinking water restrictions – you may drink the lake water as usual.
• No recreation restrictions exist – you may swim, ski, etc., in the lake immediately after application.
• There are no turf irrigation restrictions – you may water your lawns with treated lake water.
  
• YES! Restrictions exist for ornamental and broadleaved plants or crops:
  If your intake lies within one-quarter mile of a treatment area, do not use lake water to irrigate your broadleaved plants starting the day of application. Wait until ProcellaCOR levels are below 2 parts per billion* to resume lake-water irrigation.
  
  *ISDA will collect water samples approximately 3 days after the application, and a contracted laboratory will evaluate them. When the results are available, ISDA will immediately publish them on the 2024 Annual Treatment Map website.  

How will you know whether your water use will be restricted or not?

The best strategy is to explore the 2024 Annual Treatment Map. There, the shaded circles around the yellow polygons mark the area within one-quarter mile of the chemical treatment area(s). This is the notification area. 

If your water intake does not lie within a notification circle, this treatment does not require you to restrict your use of lake water.

Treatment can affect the water rights holders whose intakes lie within the circles, so they will receive 14-day advanced notices via mail. In addition to the required 14-day notice, ISDA’s contracted applicator will post a paper courtesy notice on docks within the notification area 24 hours before the treatment.

Diver-assisted weed removal imposes no restrictions on water use. Therefore, if your water rights place your intake near a diver-assisted treatment area, you will not be notified of the treatment date.

ProcellaCOR PLUS Prevention

While ProcellaCOR has proven to be an effective, targeted treatment of Eurasian Watermilfoil, it is one strategy in a larger weed-management plan. Ultimately, ProcellaCOR is most effective when used alongside proactive strategies to reduce the spread of invasive plants.

Learn to recognize the most prevalent invasive and noxious species in Hayden Lake: Eurasian Watermilfoil and Curlyleaf Pondweed. Avoid spreading weeds by routinely inspecting and cleaning boats and other equipment used in and around water following use. And, if you choose to take weed matters into your own hands, hire experts, i.e., certified divers to manually remove weeds or an IPDES-permitted herbicide applicator, and drop Jeremey Varley of ISDA a note to let them know what and where treatments are taking place. Because herbicides carry EPA dosage limits and notification requirements, putting herbicides into Hayden Lake, a public waterway, without a permit is against the law and endangers neighbors and natural aquatic life.