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Aquatic Plant Control   Michigan Riparian Article (November 2003)

Aquatic Plant Control

The objective of a sound aquatic plant control program is to only remove nuisance and invasive plant species that adversely impact lake ecology and inhibit recreational use. Under no circumstances should an attempt be made to remove all plants from a lake.

Controlling the spread of Eurasian milfoil in Houghton Lake is an essential component of ongoing management efforts. Because of its ability to spread by fragmentation, mechanical harvesting is generally not recommended to control Eurasian milfoil in that it can promote the spread of the plant. Most often, Eurasian milfoil is controlled via the application of a systemic herbicide. Systemic herbicides kill the entire plant, unlike contact herbicides that leave the roots intact.

After several years of study by the U.S. Army Corps of Engineers and others, Houghton Lake was treated in 2002 with a systemic herbicide called fluridone (trade name Sonar) to control Eurasian milfoil. The fluridone was applied to the entire surface of the lake in two separate treatments spaced approximately three weeks apart. Vegetation surveys of Houghton Lake conducted since the treatment indicate that fluridone was highly effective and Eurasian milfoil has since been found only in small portions of the lake. Annual spot-treatments of Eurasian milfoil beds are being conducted to help prevent re-infestation of the plant. The control of Eurasian milfoil in Houghton Lake has improved recreational use and benefited both the lake ecology and the local economy.

Plant Control History
In addition to herbicide treatments, mechanical harvesting has been performed to control nuisance growth of plants other than Eurasian milfoil, and over 33,000 milfoil weevils (Euhrychiopsis lecontei) have been stocked in and around Houghton Lake. Milfoil weevils feed selectively on Eurasian milfoil while ignoring other plants.

Monitoring and selective control are being conducted on an annual basis to ensure Eurasian milfoil does not regain dominance in Houghton Lake.