IDAHO FALLS — Sgt. Karl Casperson’s diving team from the Bonneville County Sheriff’s Office is customarily called to find drowning victims.
On the morning of Sept. 21, however, a group of his divers scoured the bottom of Gem Lake for an invasive weed that’s been causing problems for local irrigators.
Divers searched within 12 feet of known infested banks, clearing out patches of flowering rush and stuffing the perennial plant into onion sacks. The weeds were later piled and burned. The divers’ time and the cost of their stored oxygen was covered by $3,000 in state and federal grant funding, obtained by the Bonneville County Weed Department.
“Any time you can spend in the water is time you can familiarize yourself with your gear,” Casperson said. “It’s definitely a service, too, we can perform and a good benefit.”
Workers from the Idaho State Department of Agriculture — including Matt Kreizenbeck, who discovered the Gem Lake infestation about three years ago — Idaho Falls Power staff and employees of the Bonneville and Bannock county weed departments also helped to remove weeds.
Bonneville County Weed Department Superintendent Jeffrey Pettingill said the dive team also spent a morning removing weeds from the reservoir last fall and filled four truckloads with flowering rush. This year, they filled a single truckload, a sign to Pettingill that the mechanical removal program is working.
In Eastern Idaho, the weed is found from Gem Lake downstream to American Falls Reservoir. It spreads when rhizomes break off and float until taking hold in slack water.
“We are really dumbfounded as to why it’s not downstream of American Falls Reservoir,” Pettingill said.
Weeds have also spread from Gem Lake into canals serving the Snake River Irrigation Co. and Woodville Canal Co.
“I can see within a year or two it’s going to really plug our canal system off and we’re not going to be able to get water to the ends of the canal,” said Deverle Wattenbarger, president of Woodville Canal Co.
Hoping to at least set back flowering rush in Woodville Canal, Pettingill intends to treat it with herbicide from Oct. 17-18, after the system is shut off for the season. John Madsen, a leading flowering rush researcher with University of California, Davis, is scheduled to assist with the herbicide application.
Pettingill believes flowering rush, a native to Asia imported as an ornamental due to the attractive, pink blossom it produces, has spread in Eastern Idaho from landscaping in private ponds.
Dave Herter, superintendent of Bannock County Noxious Weed Control, said flowering rush was found this spring in some Fort Hall Irrigation Co. canals. The irrigation company has asked to take the lead on removal, but Herter said his staff will be available to help pull weeds.
“It was a good deal to come up and see how (Bonneville County) deals with it,” Herter said. “Maybe we can follow their lead with some of it.”
Hillcrest High School student Michael Klingler is producing a video on Pettingill’s efforts and also organized public meetings and notified irrigators about scheduled management actions for his Eagle Scout and senior projects.