A northeast Kansas lake recently underwent chemical treatment for a species of aquatic vegetation considered invasive by some and necessary by others.


Lake Shawnee, located along S.E. Croco Road in Topeka between S.E. 29th to the north and S.E. 45th to the south, was treated with Sonar Genesis aquatic herbicide on Monday to help control Eurasian watermilfoil present in the lake.


The lake won’t be closed as a result of the treatments, according to Mike McLaughlin, communications and public information supervisor for Shawnee County Parks and Recreation, though signs were posted about the work being done.


The treatment Monday came as a bit of a surprise for the county. The Missouri-based company that secured the $103,800 bid for the project, Aquatic Control Inc., hadn’t originally scheduled to do it that day. But as time slots opened up this week, Aquatic Control was able to squeeze the treatment into its schedule.


The decision to solicit bids for the treatment of Lake Shawnee was made Aug. 29, 2019, though the item was originally set to be voted on during the Shawnee County Commission’s Aug. 19 meeting.


However, criticism regarding the use of herbicide in Lake Shawnee by longtime outdoors writer and fishing icon Ned Kehde, of Lawrence, in a Topeka Capital-Journal article prior to the meeting led to the issue being tabled until after the Parks and Rec Advisory Board could gather public input at its Aug. 27 meeting at the Shawnee North Community Center.


Kehde, the namesake of the popular Ned Rig lure, preferred using manual or mechanical means to control the weed rather than something as indiscriminate as herbicide, as he said that during past treatments significant patches of American water willows were killed, as were burgeoning patches of American pondweed, coontail and bushy pondweed. None of those are labeled invasive species.


He also argued that bass and other species of fish use the watermilfoil as shelter and for cover when hunting.


Kehde first became vocal about the issue when Douglas County decided to stop using the herbicide Ecomazapyr to kill vegetation after 20 trees died near the shoreline of Lone Star Lake, apparently of herbicide poisoning.


Shawnee County previously used a different herbicide, Navigate, to control Eurasian milfoil, but switched to the milder Sonar Genesis after hearing Kehde’s concerns. Richard Sanders, district fisheries biologist for the Kansas Department of Wildlife, Parks and Tourism, reportedly told the advisory board that Sonar Genesis is a slow-acting herbicide that doesn’t affect fish populations as much.


The bid, awarded in November, also included several "bump" treatments to be undertaken at later dates, sort of like a booster shot for herbicide.


"Our plan for Lake Shawnee has been to do a treatment of the full lake every several years with bump treatments in between to control the growth and spread of the watermilfoil," McLaughlin said in an Aug. 18 Capital-Journal article.


McLaughlin also said the Eurasian watermilfoil first arrived in Lake Shawnee in 2011 and was treated in 2012 and 2016. A single treatment usually lasts three to four years, he said. The county’s most recent spot treatment with Navigate was in 2018.