Noxious weed assaults taking shape

SANDPOINT — If you see something, say something.

That's the message state and local noxious weed managers are sending to Bonner County residents as they start drawing up plans to target infestations in 2016.

"We haven't treated with herbicide in Pend Oreille for two years now," said Tom Woolf, aquatic plants manager for the Idaho State Department of Agriculture.

Eurasian milfoil and flowering rush will be the prime targets of chemical and non-chemical assaults.

Woolf said milfoil-control efforts will be directed toward parts of the lake that see year-round use, such as Ellisport Bay in Hope.

“We may approach treatment in those areas,” said Woolf.

However, Woolf and Bonner County Noxious Weed Superintendent Brad Bluemer want to hear from residents who are aware of problematic infestations. Control efforts can only be directed at weed species listed as noxious in the state of Idaho.

Woolf also anticipates some milfoil-eradication work at Priest Lake with spot treatments and diver dredging.

The city of Sandpoint, meanwhile, is keeping up its herbicide-free attack on Eurasian milfoil and flowering rush at City Beach. Rush-centric diver dredging in 2015 rid swimming areas of up to 2 tons of biomass, according to Jared Yost, the city’s noxious weed director.

“They’re pretty successful in removing biomass. We haven’t seen great success in really knocking plants back. What we have been able to do, though, is manage it well for recreation and safety,” said Yost.

The city also uses bottom barriers to choke out milfoil and is considering the use of a mechanized harvester, which can be effective if fragmentation of the plants can be contained.

Officials are also reminding waterfront landowners that they are not powerless in the fight against aquatic noxious weeds. The Idaho Department of Lands allows landowners to install up to five 10-foot by 10-foot bottom barriers to control milfoil around their docks.

The panels have to be removed annually so they don’t damage soil in the lakebed. Woolf said ISDA is working with the U.S. Army Corps of Engineers and the U.S. Fish & Wildlife Service in experimenting with the use of burlap.

“Using  burlap, you wouldn’t have to take it out and that’s the advantage of it,” said Woolf.

Flowering rush is too hardy for bottom barriers, although digging the weeds up has proven effective at keeping infestations at bay. The Idaho Lakes Commission organizes off-season digs to keep high-traffic areas clear and to teach people removal technique.

Bluemer said persistence pays off with digging around docks.

“If they stay on top of it and dig it out every year, you’d probably never have a big problem. But you’ve got to stay on top of it,” he said.

Flowering rush, which was introduced to North America via ornamental plant trade and freighter ballast, first appeared in the Pend Oreille system in 2007 as a several-acre infestation.

“Now, just about everywhere we look we find flowering rush and every year there’s more. It’s going to continue to be an issue,” said Woolf.

Herbicide treatments on flowering rush have been unsuccessful until recently, when Bluemer discovered that treating the plants with herbicide when they’re exposed during the winter drawdown can be effective in harming flowering rush.

The discovery touched off a three-year research project currently under way at the Clark Fork Driftyard. It is being coordinated by the corps’ research division and three of the top aquatic plant researchers in the nation.

The research is examining what herbicide combinations and application rates are most effective in killing flowering rush. The research includes extensive core sampling.

“It needs to run for three years for full scientific data and then it will have to go before a peer-review committee,” Bluemer said.

However, preliminary data suggest success. Aerial photos plainly show where flowering rush has been killed, which is supported by biomass evaluations.

“The total biomass per square meter was 669 dry grams in the untreated area and 27 grams in the treated area,” said Bluemer.

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See something? Say something

Residents who are aware of areas infested with noxious weeds can email Bonner County Noxious Weed Superintendent at bbluemer@bonnercountyid.gov. For noxious weed identification tips, visit www.idahoweedawareness.com