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WSU/Pend Oreille Extension introduced the Sense of Place series in 1999, with a focus on place-based stewardship education. Since 2001, a partnership with the Kalispel Tribe of Indians Natural Resources Department (KNRD) has supported this newsletter and allowed us to expand class offerings through EPA funding. Further staff support comes through Renewable Resources Extension Act (RREA). Many thanks to our partners and to you, our readers, for your continued enthusiasm for "digging" into the natural history and culture of this part of the world.

Worse than Milfoil? Invasives in the Pend Oreille River

by Sharon Sorby, Pend Oreille County Weed Board Coordinator

Eurasian milfoil (Myriophyllum spicatum), is one of the worst aquatic plant pests in North America. It spreads fast through fragmentation—a tiny sprig dropped into a clear waterbody can soon become a milfoil jungle. By late summer in 1982, Eurasian milfoil covered approximately 200 acres of the Pend Oreille River. By 1988, it had infested over 2400 acres. The rapid spread of Eurasian milfoil is a cautionary tale to alert us to possible new invaders.

Zebra mussels (Dreissena polymorpha) and Quagga mussels (Dreissena bugensis) are native to the Caspian Sea. They were introduced into the Great Lakes in the mid 1980’s in ships ballast water and have spread to several popular western lakes including Lake Mead and Lake Havasu. Where introduced, these small shellfish reproduce prolifically, threatening native fish and costing taxpayers millions by clogging power plant, irrigation and other water intakes. Because the mussels can live out of water for up to a month they may be easily transported on recreational and commercial boats. They can be attached to hulls and propellers, live as microscopic larvae in bilges and live wells, or can be introduced with plants attached to boat or trailer. So far, none have been detected in the Pend Oreille system. Preventing introduction is the goal of boat check stations like the ones in Idaho or the volunteer monitoring program on Diamond Lake. A lot rests on the diligence of recreationists in effectively cleaning boats and trailers when moving to a new body of water.

A new invasive weed that is poised to be a problem is flowering rush (Butomus umbellatus). This weed can form dense stands, and since it spreads rapidly through rhizome fragmentation, extreme care must be taken in digging and removing the plant. It has become established in Lake Pend Oreille, and was first found in the Pend Oreille River downstream of Albeni Falls dam in 2010 and removed. A survey conducted with volunteer help last summer found at least 30 clumps of the weed distributed from Newport to Cusick. Boater help is needed in detecting and reporting new spots.

Besides clogging waterways for boating, fishing and other water recreational activities, the plants are the perfect habitat for the snail that carries the parasite that causes swimmer’s itch. It is already present in some of the rush clones that have floated in from upriver. Removal of the clones may prevent the parasite from becoming established in the lower Pend Oreille River.

Yellowflag iris, (Iris psuedocorus) has become common on several local lakes and in portions of the Little Spokane River. An escaped ornamental, it outcompetes the native vegetation and is difficult to remove once established. Several areas along the Pend Oreille River are being treated this fall and help is needed to detect new infestations.

Many other potential aquatic invaders could also give Eurasian Milfoil a run for the money in impacting fish habitat, water quality and recreation—hydrilla, Brazillian elodea, parrotfeather milfoil and water hyacinth are a few that come to mind.

Please contact the Pend Oreille County Weed Board if you have questions about identifying aquatic weeds or to report new areas of invasives along the river. You can stop by the Weed Board and Extension Office at 418 S Scott (next to the Courthouse) to pick up information about identifying these non-native invasive pests, phone 447-2402 or email ssorby@pendoreille.org

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