Special Projects


In addition to the monitoring and control of over 5,000 noxious weed infested sites in Thurston County, special projects are also performed  by the Noxious Weed Control Agency.

Brazilian Elodea (Egeria densa) removal on the Chehalis River

Brazilian Elodea is a non-native submersed freshwater aquatic plant. It was found in 1998 in the Chehalis River while surveying for purple loosestrife and parrotfeather. It is the only infested site in Thurston County. It was most likely introduced into the river by someone dumping the contents of their home aquarium into Plummer Lake, in Centralia. The plant has spread 15 river miles downstream from the point of introduction.

The Noxious Weed Control program began removing individual plants as early as 1999. Hand removal continued to 2003Crane on bridge removing weeds when the infestations became so large that individual hand removal was no longer practical.

A diver dredging pilot project funded by Department of Natural Resources was conducted in 2004. The project was expanded in 2005 with funding from U.S. Fish and Wildlife.  In 2006 the Chehalis Tribe joined the project, and began removal of elodea in the Chehalis River near Centralia. In 2007 the Department of Ecology provided funding to the Chehalis Tribe and Thurston County for increased removal efforts.

Removal will increase water movement resulting in higher dissolved oxygen. In 2007, oxygen levels were measured before and after removal efforts.  Following removal, oxygen levels increased 7.75%. Removal will also decrease sediment retention. The method of removal includes diver suction dredging to remove the entire plant and root structure.  The plants are then transported away from the river.

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Eurasian watermilfoil (Myriophyllum spicatum) removal on Black LakeDiver with Milfoil

Eurasian watermilfoil was first identified in Black lake in 2004. Similarities with other native plants made it necessary for scientists to perform DNA analysis to confirm the species as the invasive Eurasian water milfoil and not the native plant Northern milfoil. In November 2005, Eurasian watermilfoil was confirmed as the species collected at Black lake in 2004.

A project funded by the Washington State Department of Ecology  includes a thorough survey of the lake as well as manual diver removal of plants found. If the grant project is successful we may be able to prevent milfoil from establishing and taking over the recreational uses as well as the wildlife habitat of Black Lake.

[Back to the top]Purple Loosestrife Weed

Purple loosestrife (Lythrum salicaria) monitoring on Capitol lake

Great progress has been achieved in control of this invasive aquatic emergent species. Purple loosestrife threatens 44 native species nationwide including several endangered and sensitive species. Multiple private ownerships of the Deschutes River watershed, as well as Washington Department of General Administration have all worked towards eradication of this invasive species on Capitol lake.

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Biological Control EffortsBruchidius villosus

Since the early 1970s, biological controls have been used as a part of the weed program’s work plan. Following rigorous screening by the U. S. Department of Agriculture, colonies of species-specific insects have been released annually. Thurston County’s weed program has collected, distributed, purchased, and contributed to research, in order to obtain additional biological agents to assist in the control of widespread noxious weed species.

Biological Agent Distributions:

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Contact Us

Address questions or comments to: tcweeds@co.thurston.wa.us

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