Legend Lake, located on the Menominee Indian Reservation, is a chain of interconnected water bodies totaling 1285 acres. In 2001, Eurasian watermilfoil (Myriophyllum spicatum) was first identified in the system. During the following four years, milfoil spread rapidly throughout the lakes. Aquatic plant management efforts were limited to small-scale herbicide treatments and harvesting for navigational purposes. In the fall of 2005, a survey conducted by Cason & Associates, LLC biologists identified a total of 538 acres of Eurasian watermilfoil.
The following May, 218 acres of Eurasian watermilfoil in selected lake basins were treated with Navigate® (granular 2,4-D) at a rate of 100 lbs/acre. A staggered treatment approach was chosen to not only control Eurasian watermilfoil but also minimize the large-scale treatment impact to the ecological health of the system; particularly dissolved oxygen levels and the native plant community. This was confirmed with extensive pre- and post-treatment monitoring starting in 2006 and continuing to the present. Milfoil (660.2 acres) continued to expand in untreated lakes. By the fall of 2006, a total of 660 acres of milfoil were documented. The following year, 246 acres were treated in the previously untreated lake basins. By the end of 2007, nearly 500 acres of milfoil still remained in the Legend Lake system. A decision was made to change the treatment approach and target all known Eurasian watermilfoil beds the following spring. A review of the water quality and aquatic plant data collected showed minimal ecological impacts as a result of the treatment.
In the spring of 2008 a total of 498 acres of Eurasian watermilfoil were treated using Navigate® at rates of 100 – 150 lbs/acre. Rates varied depending upon the size of each milfoil bed. By the fall of 2008, a total of 156 acres of Eurasian watermilfoil remained in the entire system. Treatments in 2009 further reduced milfoil to 129 acres and by the fall of 2010, 119 acres remained. From its peak distribution in 2006, Eurasian watermilfoil has been reduced by nearly 82% in the Legend Lake system. This can be attributed to accurate and detailed mapping, extensive pre- and post-treatment ecological monitoring, and precise and timely treatments. With numerous agencies and organizations involved including the Menominee Indian Tribe of Wisconsin (MITW), Wisconsin DNR, Menominee County, and Legend Lake P&R District (LLPRD), communication has also played a vital role in this project.
Because of the problems created by Eurasian watermilfoil over the past decade, the LLPRD developed an aquatic plant management plan entitled Legend Lake Aquatic Plant Management Plan 2006-2008. The LLPRD and its consultants (Cason & Associates and AECOM) developed this management plan in cooperation with the MITW and the Wisconsin DNR. Each year, Cason & Associates works with the LLPRD, WDNR, and MITW to update this plan to meet the changing lake management needs.
The Legend Lake project involved the largest treatment of Eurasian watermilfoil in the state of Wisconsin. Cason & Associates, LLC continues to work closely with the LLPRD and government entities to make further progress managing invasives on the lake.
For more information about this project or our lake management services, contact us at (877)-309-8408.
Article originally published in the Cason & Associates Spring 2011 newsletter.