State officials have treated a 19 acre section of the state’s deepest natural lake to kill a fast-spreading, invasive plant.
Mike Hawkins, a fisheries biologist with the Iowa Department of Natural Resources, says Eurasian watermilfoil was discovered in three canals on West Okoboji Lake this summer. “The Miller’s Bay canal system, the West Okoboji Harbor system and a very small area that we call Lazy Lagoon on the west end of West Okoboji,” Hawkins says.
State officials spent a few weeks making sure all rules and guidelines were met before applying herbicide in the lake, which has a special designation. “Not only is it an ‘outstanding Iowa water,’ but it’s also a drinking water source for much of the community up here,” Hawkins says, “so there are a lot of checks before anything can be applied or discharged into West Okoboji Lake.”
A fast-acting herbicide which targets a few invasive plants was applied Tuesday. “We can apply that herbicide and not attack other native plants in the area,” Hawkins says, “and just go after the Eurasian watermilfoil.”
A far larger, 2300 acre area of East Okoboji Lake was treated by a different herbicide a year ago and it appears to have wiped out that infestation. “It was widespread, but not very dense so we were catching it at the very beginning of an infestation,” Hawkins says. “…The State of Iowa’s Aquatic Invasive Species Program has been extremely aggressive with Eurasian water milfoil and keeping it from spreading in the state and we’ve gotten pretty good at treating this plant.”
The plant forms thick mats in the water, blocking out sunlight and killing off underwater plants that are food for fish. Boats and trailers carrying fragments of Eurasian watermilfoil are introducing the invasive plant to lakes. Hawkins says that’s why it’s important to either wash off boats, trailers and fishing wells in the boat at a car wash that has hot water or park boats and trailers for at least five days on dry land.