Eurasian Watermilfoil (Milfoil)

2022 Milfoil Treatment Plan Update

The Newman Lake Flood Control Zone District (NLFCZD) has scheduled an approximately 27-acre herbicide treatment to control Eurasian watermilfoil within Newman Lake. Please click here to see to view the herbicide treatment area map. The updated treatment date will occur on August 18, 2022, weather permitting.

The herbicide which will be used, ProcellaCOR EC, is a selective, systemic herbicide approved by the Washington State Department of Ecology (DOE) for aquatic use. The contracted applicator, AquaTechnex, will post notices on beaches and docks within ¼ mile of the affected areas 48 hours before the treatment date. 

 See below for a list of water restrictions related to the herbicide treatment:

• All lakefront property owners within ¼ mile of treated areas (see map here) will receive an updated mail notification ten days before the planned herbicide treatment.
• District staff will request that lake residents refrain from boating near the contractor’s boats while they are treating to minimize wave action and increase herbicide efficacy.
• There are no swimming, boating, or fishing restrictions after the herbicide has been applied.

The reason for the later-than-typical treatment date in the season is to increase the efficiency of the treatment, i.e. utilize District funds for treatment such that there is a higher degree of success. This year, the lake level was quite high and water clarity poor due to the above-average rainfall in the spring. Thus, we could not perform an accurate survey to identify high-density clusters. This led District staff to postpone the treatment until a more accurate survey could be obtained. Once growth was visible, a plan was developed, and a treatment date was scheduled for August 18th. 

Furthermore, the choice to treat exclusively with herbicide again this year, as opposed to diver suction weeding, is to increase the long-term impact of removal and decrease the cost of treatment. ProcellaCOR kills the targeted invasive plants and their associated roots, therefore, inhibiting the plants from re-growing in future seasons. Diver suction weeding only removes the branches of the invasive plants, allowing them to re-grow the next year.

As many of you know from previous newsletter articles and mailings, Eurasian watermilfoil, an invasive, non-native aquatic weed, was discovered in Newman Lake at the outlet gate area in the fall of 2002. The plant is extremely invasive and, left unchecked, can take over a lake, pushing out native aquatic species and growing in dense mats up to the surface from depths of 15 feet. 

The NLFCZD is continuing this program for the lake's health, aimed at the control and eradication of this invasive species. We appreciate your help and cooperation with these efforts.

Web Map of Treatment Area: ArcGIS Newman Lake Milfoil