A two-state flotilla, armed with its enemies list, is poised to launch a multiday assault on numerous invasive species that threaten the St. Croix River separating Minnesota and Wisconsin.

Posted at points stretching more than 40 miles, inspectors will staff three decontamination boats on each side of the river July 14 and 15 in a search-and-destroy mission against such invaders as zebra mussels, Eurasian watermilfoil, curly leaf pondweed, bighead carp, rusty crayfish and Asian clams.

These invasives "are a threat to the overall health of the St. Croix River and its tributaries," read a statement issued Wednesday by the St. Croix River Association, which will contribute four interns to the effort.

"The St. Croix is one of the cleanest tributaries to the Mississippi River," the statement continued. "It is a high-value fishery. ... The introduction of aggressive invasive species into this complex system threatens the ecological integrity of the rivers as well as the unique cultural resources and our outdoor heritage."

The six decontamination boats are equipped with high-pressure and high-temperature wash units that will be trained on watercraft at public access points without allowing any of the water to run off into the river.

The Minnesota Department of Natural Resources (DNR) will post two wash units at landings in Washington County -- the St. Croix Boom Site on Highway 95 just north of Stillwater, and at St. Croix Bluffs Regional Park near Afton -- and another will be operated by Chisago County at the Osceola Landing.

Wisconsin's DNR will staff its units at landings in Prescott, Hudson and St. Croix Falls.

Along with being offered a thorough cleaning for their watercraft, boaters also will be advised on how they should properly clean, drain and dry their vessels to keep the invasives from spreading.

Paul Walsh • 612-673-4482