Eurasian Watermilfoil (Milfoil)
2021 Milfoil Treatment Plan Update
The Newman Lake Flood Control Zone District (NLFCZD) has scheduled an approximately 60-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 September 13, 2021, weather permitting.
The herbicide which will be used is 2, 4-D amine, a selective, systemic herbicide approved by Washington State Department of Ecology (DOE) for aquatic use. The contract applicator, Aquatic Weed Solutions, will be posting 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 located within ¼ mile of treated areas (see map here) will receive an updated mail notification 10 days in advance of the planned herbicide treatment.
• There will be drinking and irrigation water intake restrictions in place, i.e. no drawing water from the lake in affected areas for up to 21 days after treatment.
• District staff will test the concentrations of 2, 4-D after 7 days. Historically, at 7 days, the concentration has dropped low enough that the restrictions can be removed.
• The Washington Department of Fish and Wildlife public boat launch access will be closed from the night before treatment, until 24 hours after treatment.
• District staff will request that lake residents refrain from boating and swimming in the affected areas of treatment until 24 hours after treatment.
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 treatment success. This year, a milfoil survey conducted in late May found that much of the plant mass had not grown enough to be spotted via boat, which means that positively identifying where to treat was not possible. 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 4th. However, this treatment was postponed due to a multitude of community complaints regarding the timing of the treatment. Consultation with Washington State Department of Ecology has confirmed that fall treatment is appropriate and effective.
Furthermore, the choice to treat primarily with herbicide this year, as opposed to Diver Suction Weeding, is to increase the long-term impact of removal and decrease the cost of treatment. 2, 4-D amine 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 health of the lake, aimed at the control and eradication of this invasive species. We appreciate your help and cooperation with these efforts.