Love For Our Iowa Great Lakes

The 2018 plan treated 61 acres of curly leaf with a combination of mechanical harvesting and the use of an aquatic herbicide. 4.25 miles of shoreline was treated.

The beautiful clear, blue waters of the Iowa Great Lakes are a summer mainstay for locals and residents! The Okoboji chain is perfect for lounging at the beach or enjoying a sunset cruise on the boat. Kayaking and jet skis are just as popular and it isn’t uncommon to see the sails of the Okoboji Yacht Club on West Lake Okoboji.

These glacier-carved lakes are especially popular in summer but have plenty to offer in the fall, and it’s easy to see why the region is often considered a well-kept secret outside of the Midwest.

The Iowa Great Lakes include Iowa’s largest natural lake, Spirit Lake and five interconnect lakes: West Okoboji, East Okoboji, Upper Gar, Lower Gar, and Minnewashta. Spring-fed West Lake Okoboji is the centerpiece of the five chain lakes, has a beautiful shade of blue and in areas is 134 feet deep.

The problem is portions of the Iowa Great Lakes have been claimed by a monster weed during the spring, creating havoc with water access and producing navigation issues.

Suddenly, the region’s clear, blue waters seem to have a problem. The question asked is should we panic?

“Curlyleaf pondweed has been in our lakes since the middle of the last century, but conditions have allowed it to gain a foothold growing to form dense mats impacting recreation and access,” said Mike Hawkins, Iowa DNR fisheries biologist. “This plant is common throughout the Midwest, causing similar issues on hundreds of lakes.”

Curlyleaf pondweed also has some positive attributes for the lakes, like clearing the water and providing good aquatic habitat.

Unlike native plants, curlyleaf pondweed germinates in the fall, grows under the ice and hits the surface by early May. The weed dies back naturally in late June; bringing back the clear, blue waters many consider a natural component of the area’s lakes.

Cooperative Management Plan Developed

Terry Wilts, with the East Okoboji Lakes Improvement Corporation, has helped spearhead the management effort over the past few years and explains there are no easy options to solve this problem, but there are means towards eliminating frustrations over navigation issues or access to the water.

“This plant impacts hundreds of acres. As a team, we realize we can’t treat all of it, but are prioritizing our funds and efforts,” Wilts said. “The 2019 plan builds on efforts from past years. We’ve taken what we’ve learned and are applying this knowledge to maximize our impact.”

Wilts, along with other members from Dickinson County, local cities, lakes associations, Iowa Lakeside Lab, drinking water utilities, and the Iowa Department of Natural Resources (DNR) have partnered together in hopes of finding a solution and easing the impact of the weed on the Lakes.

The 2018 plan treated 61 acres of curlyleaf with a combination of mechanical harvesting and the use of an aquatic herbicide. The project stayed on budget and within the proper time frame, despite last year’s late ice out. Twenty acres were treated along the shoreline with an aquatic herbicide and 41 acres (one million pounds) was harvested using a mechanical plant harvester.

The herbicide was used more than five miles from any drinking water intake.

In 2019, the plan remains the same but has increased management efforts, including increasing herbicide treatment to 60 acres while still proposing mechanical harvesting of 25 acres.

First Phase Started April 26

On April 26, the DNR and the East Okoboji Lakes Improvement Corporation (EOLIC) began the first phase of the curlyleaf pondweed 2019 management strategy for the Iowa Great Lakes.

The cooperative initiative treated 60 acres of curlyleaf along shorelines with an herbicide approved for use on lakes, with a goal of providing some relief around docks and boat ramps.

“Our first use of the herbicide in 2018 treated the areas just outside of the dock on about 4.25 miles of shoreline,” Hawkins said. “Last year’s application on the north end of East Okoboji Lake and Lower Gar Lake proved safe and effective treatment. This year we treated a little over eight miles of shoreline.”

“Another five miles of trails were created using a commercial plant harvesting system in late May,” says Hawkins. “We also did a 30-acre block treatment, using a combination of herbicide and harvesting in the North Bay of East Okoboji Lake to reduce the amount of plant material that dies off in June and help prevent a fish kill from low oxygen.”

Although curlyleaf pondweed is widespread and causes problems throughout the United States, management strategies are mostly limited to spot treatments while attempts to eliminate it have failed. Larger treatment area control is being investigated and evaluations are underway in Iowa and other states.

The DNR and project partners want to emphasize the importance of not illegally applying herbicides.

“We can’t tolerate lakeshore residents illegally applying herbicides. Iowa law restricts their use and only the DNR has the authority to treat plants in the lake with a herbicide. Everyone living or vacationing in this area gets their drinking water from our lakes. Not following the law endangers that precious resource,” said Eric Stoll, with Milford Utilities, which supplies drinking water for thousands of customers in the region.

Lakeshore property owners can remove plants around their docks and hoists without a permit. The plants can be cut, raked, or harvested using mechanical means only. It is not legal for private citizens to treat plants with chemicals in public waters.

Funding for the project comes from local contributions to the East Okoboji Lakes Improvement Corporation and the DNR’s Marine Fuel Tax Fund, which is dedicated to improving boater access in Iowa.

Most importantly, there’s no need to panic. While an annoyance, through efforts of numerous organizations, the curlyleaf pondweed is being managed and new solutions being explored. And by July 4th weekend, the gorgeous blue waters we all love should be free of the monster weed and back to the beauty we love and enjoy.

For more information on curly pondweed, contact Mike Hawkins, fisheries biologist, Iowa Department of Natural Resources, 712-336-1840. To donate towards management efforts of curly pondweed, contact the EOLIC at or Iowa Great Lakes Association at