The Iowa Department of Natural Resources (DNR) and partners at the Iowa Lakeside Laboratory recently discovered and treated a small, isolated population of Eurasian watermilfoil growing in the canal system south of Miller’s Bay. No Eurasian watermilfoil was found in the main lake of West Okoboji Lake or the other lakes in the Iowa Great Lakes chain.
“After the discovery of Eurasian watermilfoil deep in the West Okoboji Lake canals, we acted swiftly to control the plant using an effective, safe, milfoil-focused herbicide treatment,” said Andrew Carlson, fisheries biologist for the Iowa DNR. “With required permits already in place, we were in a prime position to respond rapidly to control this highly invasive plant and protect the aquatic ecosystem. We are thankful for community funding and staff at the Iowa Lakeside Laboratory for helping isolate the plants.”
The DNR is asking boaters and other users in these areas to be extra vigilant to help prevent the spread of these invasive aquatic plants elsewhere in West Okoboji or the other lakes in this chain.
Iowa’s Aquatic Invasive Species Program has been a national leader in control efforts to stop Eurasian watermilfoil for more than 30 years. The Iowa DNR Aquatic Plant Management team monitors the vegetation in the Iowa Great Lakes each year.
Eurasian watermilfoil, an invasive rooted aquatic plant native to parts of Europe and Asia, can spread quickly and outcompete beneficial native plants. It reproduces by fragmentation, which means small pieces of it grow into new plants and form thick beds.
Clean, Drain, Dry is a simple three step process that boaters need to follow every time they move from one body of water to another.
- CLEAN any plants, animals or mud from the boat and equipment before you leave a water body. With the current infestations in the canals and lagoon, you must also check boat props and other parts of the boat where vegetation fragments could get caught before entering the main lake.
- DRAIN water from all equipment (motor, live well, bilge, transom well, bait bucket) before you leave a water body.
- DRY anything that comes into contact with water (boats, trailers, equipment, boots, clothing, dogs). Before you move to another waterbody either: Spray your boat and trailer with hot, high-pressure water; or Dry your boat and equipment for at least five Days.
Never release plants, fish or animals into a water body unless they came out of that water body and empty unwanted bait in the trash.
It is illegal to possess or transport prohibited aquatic invasive species, such as Eurasian watermilfoil, in Iowa. Boaters must also drain all water from boats and equipment before leaving a water access and must keep drain plugs removed or opened during transport.
Find more information about aquatic invasive species and a list of infested waters in the 2026 Iowa Fishing Regulations booklet or on the DNR’s website at www.iowadnr.gov/ais.