Bonner milfoil program gaining strength

SANDPOINT — Leading-edge technology and established scientific methods are converging in Bonner County’s battle against Eurasian milfoil.

The county’s use of herbicides in Lake Pend Oreille coincided with a pretreatment survey conducted by Mississippi State University’s GeoResources Institute and a U.S. Army Corps of Engineers dye tracing project, which studied the behavior of the lake’s water flow.

Meantime, the herbicides being used to kill the aquatic noxious weed are being applied in a revolutionary way. Clean Lakes Inc., the company the county hired to apply the herbicides, has developed a way of applying them at plant level instead of near the top of the water column.

“Everything’s a big plus,” Brad Bluemer, the county’s noxious weed superintendent, said of the alignment of resources. “It’s win, win, win all the way around.”

This year’s treatment program marked the debut of Clean Lake’s “LitLine” application system. The system’s name refers to a body of water’s littoral zone, the shallower near-shore areas where aquatic plants thrive.

Tom McNabb, aquatic pest control advisor for Clean Lakes, said the system was borne out of a need to apply herbicides in the strata of water where the plants are. But conventional application methods tend to involve treating from the top of the water column.

The eureka moment came to McNabb after Dr. William Haller, a University of Florida professor and acting director of the Center For Aquatic & Invasive Plants, challenged the industry to engineer a way to apply chemicals broadside as opposed to top-down.

McNabb tried weighting down drip lines so they could reach greater depths, but the hoses would usually become fouled in the tangle of weeds or when the boat turned a corner.

The solution, McNabb found, was strikingly simple: use longer lengths of hose. He discovered that longer hoses sink down among the weeds and slink through them without tangling.

McNabb proved the concept by putting a diver in the water with a video camera, footage from which showed the hoses trailing through the plant beds with ease.

“The technology was there. It just needed to go a step further,” McNabb said.

McNabb mounted 100-foot lengths of hose onto motor-driven spools and paired the assembly with a GPS-enabled navigation and chemical application system, which keeps the boat on a precise course in treatment areas and strictly regulates the flow of herbicides. If the GPS finds the boat on a course it’s already been on, for instance, the application system shuts down.

“This tracks where every drop of herbicide goes,” McNabb said as he sat before an array of digital monitors and controls panels sprouting from the deck of his boat. “You can’t get more accurate than this.”

Neither Bluemer nor McNabb believe the application innovation will win over legions of herbicide opponents who question the program’s public heath and environmental impacts. However, they hope the surveying, new application method and the dye tracing will counter the belief that the project is being done haphazardly or without any scientific compass.

Moreover, the new application method is cutting costs and the amount of herbicide being used in the lake.

“We’re using about half the chemicals,” Bluemer said of this year’s lake treatments.

The dye tracing project, which is being done by the corps’ Research & Development Center, is being completed, although officials said it’s too soon to reach any rock-solid conclusions. A report on the tracing project, which involves using a water soluble dye to track the behavior of subsurface water flow, is expected later this year.

However, the corps’ tracing project team leader, Dr. Kurt Getsinger, said preliminary observations suggest product being applied is not straying from treatment areas in certain parts of the lake.

Bluemer is grateful for the corps’ tracing project, which is expected to help the county and other agencies in the Northwest refine their treatments so they’re more effective and precise.

“The dye study essentially does away with a lot of guessing,” said Bluemer, who feels the convergence of studies and technological advancements is making Bonner County’s program one of the most intensive in the country.

“Bonner County should feel very lucky,” added Getsinger. “You don’t see projects like this.”