The Iowa Department of Natural Resources will soon apply a herbicide on the north bay of East Lake Okoboji to try to combat an invasive plant. Curly-leaf pondweed can get quite dense and impedes fishing, swimming and boating.

DNR fisheries biologist Mike Hawkins says a herbicide called Sonar has been around since 1986, but it’s never been used in the Iowa Great Lakes before.

“This is a completely different type of herbicide than we’ve been using,” Hawkins says. “It’s safety profile is extremely good. It’s used across the country in some environmentally sensitive projects. The treatment rates are down into the two-to-five parts per billion range, so it’s a very, very low dosage rate that we put on and there’s no restrictions for fishing (or) swimming.”

Hawkins says native plants in the Iowa Great Lakes are dying off, as they do in the fall, but curly-leaf pondweed is just starting to sprout and will keep growing under the ice.

“It’s an unusual plant,” Hawkins says. “Curly-leaf pondweed, the new crop of it, is now only about four-to-six inches tall, so that’s really the only aquatic plant that we’re treating at this point.”

Hawkins says the DNR may expand its mechanical harvesting of curly-leaf pondweed next year. The plant has thick roots, blooms in the spring and dies in late July.

(By Ed Funston, KILR, Estherville)