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WATERLINE - June, 2017

Hybrid milfoil comes to Washington State

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For the past few years, lake managers fighting Eurasian water milfoil (EWM) to the east of us have noticed that the plant is getting harder and harder to treat and kill. This trend started in Michigan and Wisconsin where EWM has been a problem for three to four decades. The primary tool used to target Eurasian milfoil on a large scale has been 2,4-D herbicide formulations, which have worked for years. For the past two or three years in Idaho, though, many of the treatment projects, using a variety of conventional technologies to target and treat the plant, have achieved only marginal control.

The Pacific Northwest is experiencing an expanding problem as we attempt to manage hybrid milfoil (HWM), a cross between EWM and native milfoil species.  HWM can be more aggressive than EWM and has demonstrated tolerance to some of our commonly used tools such as 2,4-D herbicide.

Last summer we were asked to take on an “EWM” infestation in Loon Lake north of Spokane. We had worked with the Loon Lake community through most of the 2000’s and EWM had been largely removed from the system by 2008. This past year we were asked to come back and help them target “EWM” which we did with a systemic herbicide that generally works on that species. Control was variable and we began to suspect that perhaps a hybrid had established. HWM looks very much like the EWM applicators have been after for years. DNA analysis is the only way to tell for sure, and we sent ten samples to a laboratory that specializes in DNA analysis of milfoils.  All ten came back as HWM.

We then helped the Loon Lake community write a grant application to the Washington Department of Ecology to develop Best Management Practices (BMP’s) for targeting this aggressive milfoil species. Loon Lake received the grant and we will be working with them this summer to implement this program. The BMP’s for this invasive species are DNA analysis, herbicide screening of the target populations, and application strategies.

Aquatechnex has used Sonar Aquatic herbicide very effectively against both EWM and HWM over the years. When targeting EWM, we have eradicated this noxious weed from a number of lakes in Washington.  Our application technique focuses on maintaining low concentrations of Sonar herbicide around the target plants for an extended period of time, typically in partial treatment designs with controlled release pelleted formulations. This strategy provides long term control in contrast to other chemical control techniques that provide short term or season-long control, but see milfoil return strongly in following years. A Sonar program for effective hybrid milfoil management can be designed for any waterbody.

One of the things we are most excited about, however, is a new technology. Aquatechnex has been working with SePRO Corporation on a new technology to target both hybrid and Eurasian milfoil in high water exchange environments. Procellacor Aquatic Herbicide is expected to receive US EPA registration in 2017 and is a promising technology to combat all forms of invasive milfoil. It will have a very low application rate, at least 100 times less than older herbicide technologies such as 2,4-D and a very short contact exposure time requirement. Aquatechnex is a SePRO Preferred Applicator and has completed the training necessary to effectively deploy this game changing new strategy when it becomes available.  Procellacor will be available for use in most Pacific Northwest states when EPA issues registration.  In Washington State it will require a permit amendment and EIS and that process is underway.