About the Study:
Perch Lake, located in Michigan's Hillsdale County, is the site of a three-year (May 2000 - December 2002) field demonstration study of the ecological impacts of herbicide use to manage nuisance weeds that interfere with lake use and have a negative impact on the natural environment. The study will help determine the ability of long-contact, low-dose applications of the aquatic systemic herbicide fluridone (SePRO Corporation's Sonar AS) to selectively control the exotic plants Eurasian watermilfoil and curlyleaf pondweed without harming the lake's water quality and native plant, fish, plankton, and invertebrate communities.

The results of the study will be used to develop a model for species-specific, low-dose applications of aquatic herbicides that can be used on other northern inland lakes to control exotic plants and enhance native plant communities while reducing lake managers' dependency on large-scale, long-term chemical treatments.

Baseline surveys of Perch Lake's plant, fish, plankton, and invertebrate communities began in June 2000 and continued at intervals throughout the summer and early fall of 2000. The Sonar AS was applied to the lake Oct. 18, 2000 by Aquatic Technologies Inc; treatment of the entire lake required only three quarts of Sonar AS. (By comparison, treatment with 2,4-D would have required 1.9 tons of granular product.) (Click here to see photos of Sonar being applied to Perch Lake.)

For up to a year after treatment, resident volunteers will collect monthly water samples, and SePRO lab technicians will analyze those samples for fluridone residue levels. U.S. Army Corps of Engineers researchers will conduct plant assessments in June and August during each of the three study years. Central Michigan University students and staff will sample water quality four times a year throughout the course of the study; they will sample plankton and benthic invertebrates twice a year. (Click here to read the latest report from Central Michigan University's team.) Mississippi State University students and staff will sample the fish population and macro-invertebrates twice a year. (Click here to read the latest report from Mississippi State University's team.)

About the Study Site:
Perch Lake is a 38-acre, predominantly spring-fed kettle lake located in Somerset Township, Hillsdale County. Approximately 50 percent of its shoreline is developed with home sites; the remainder is comprised of hardwood forests and pasture. The lake's average depth is eight feet, but depths in some areas reach nearly 14 feet. There are no surface water outlets on the lake, and Perch Lake's watershed is small, with only one intermittently flowing ditch entering the lake. The lake's size, limited watershed, and isolation make it an ideal site for ecosystem-level studies.

About the Targeted Exotic Plants:
Eurasian watermilfoil (Myriophyllum spicatum) is a rooted aquatic plant that was first introduced in the United States from Europe and Asia sometime in the 1940s and has enjoyed popularity as a decorative aquarium plant. Researchers estimate that it now has spread to 37 states and three Canadian provinces, primarily through release from aquariums and transport on boats, motors, trailers, anchors, fish stringers, and other equipment.

Eurasian watermilfoil has finely dissected, feather-like leaves with 12 to 21 leaflet pairs per leaf; the plant's leaves typically grow in whorls of four leaves each on a long, flexible stem. Northern watermilfoil, a desirable native plant, has 5 to 10 leaflet pairs per cluster. (Click here to compare the two plants.) Once introduced, Eurasian watermilfoil can rapidly overpopulate its host waters to the detriment of the native plant and animal life. Due to its rapid and dense growth pattern, milfoil often forms thick mats at the water's surface, making recreational activities difficult at best. In addition, its thick, spreading growth can out-compete native plants, destroy fish-spawning areas, and create other problems for the lake ecosystem. (Click here to see the matted growth of Eurasian watermilfoil on Perch Lake.)

Curlyleaf pondweed (Potamogeton crispus), also a rooted aquatic perennial, was introduced from Europe more than a century ago and is a commonly seen nuisance species in northern lakes. Curlyleaf pondweed actively grows under ice and snow and often is the first plant to emerge in the spring. It has reddish green leaves that are distinctly wavy along the edges and a rapid growth pattern that results in the formation of dense, monotypic mats on the surface of the water that sometimes are mistaken for Eurasian watermilfoil. After the curlyleaf pondweed flowers in mid-summer, the surface mats break apart and begin to decompose, becoming a nuisance for lake residents and further negatively impacting environmental conditions.

Like Eurasian watermilfoil, curlyleaf pondweed is spread primarily by human activities. The plant is difficult to control by conventional means because it forms propagules that remain in the sediments like seeds. Eurasian watermilfoil is a much greater problem in Perch Lake than is curlyleaf pondweed.

About the Herbicide Being Used:
Sonar AS (chemical name fluridone) is a systemic aquatic herbicide manufactured by SePRO Corporation. It is used to selectively manage certain common aquatic nuisance plants and has been on the market since 1986. Sonar works by inhibiting carotenoid synthesis in the target plant. This results in photo-degradation of chlorophyl, thereby interrupting photosynthesis and stopping the plant's ability to make food. Damage in susceptible plants usually appears in seven to 10 days after treatment; visual symptoms appear as white or pink buds and stem tips.

Depending upon the formulation, rate, and time of year it is applied, Sonar can be used to selectively control nuisance weeds while having a minimal impact on desirable native plants. The Environmental Protection Agency, which has approved Sonar for aquatic herbicide use, limits the amount of the chemical that can be used to 150 parts per billion (ppb).

For the purposes of this study, Aquatic Technologies Inc. applied the product at a rate of 8 to 9 ppb in the fall of 2000. It is estimated that, by early spring 2001, the fluridone concentration in the lake will fall to 5 to 6 ppb; if the fluridone level in the lake is found to be below 5 ppb when measured after ice thaw, Aquatic Technologies will apply additional Sonar AS to bring the concentration back to 6 ppb. Study leaders expect the fluridone concentration in the lake to have declined to non-detectable levels by mid-summer 2001.

How the Sonar is Expected to Work:
The growth patterns of Eurasian milfoil and curlyleaf pondweed differ from native plant species. Eurasian milfoil remains actively growing later in the fall than native plants and begins growing earlier in the spring. Curlyleaf pondweed remains actively growing throughout the winter and is one of the first plants to emerge in the spring, long before most of the native plants emerge.

Thus, by applying the Sonar AS in the fall, the highest concentrations of the fluridone will be taken up by the milfoil but not by the native plants, which will be going dormant. The residue concentration of fluridone that will be present in the lake in the early spring will again be taken in by the earlier-growing milfoil and curlyleaf pondweed, but not by the still-dormant natives. Such long-term (60 days), low-dose exposures to Sonar have proven extremely effective for species-specific control of Eurasian watermilfoil and curlyleaf pondweed in previous lab and field trials. By the time the native plants begin their growth cycle, the Sonar should be at low enough concentrations that what residue is left will have little effect on the native plants.


Study Cooperators:
Overall Project Direction & Final Report: Kurt Getsinger, Ph.D., research biologist and team leader, Chemical Control Technology, U.S. Army Corps of Engineers Waterways Experiment Station, Vicksburg, MS

Herbicide Permitting: Laura Esman, land and water management analyst, Inland Lakes and Wetlands Unit, Land and Water Management Division, Michigan Department of Environmental Quality, Lansing, MI

Herbicide Applications & Lake Depth Contour Mapping: Scott Jorgensen, Aquatic Technologies Inc., Okemos, MI

Sonar AS Product and FasTEST Analysis: Ed Spanopoulos, Midwest aquatic specialist, SePRO Corporation, Carmel, IN

Plant Community Assessments: Chetta Owens, research scientist, Analytical Services Inc. (stationed at USAERDC Lewisville Aquatic Ecosystem Research Facility, Lewisville, TX)

Fish Community & Macro-Invertebrate Assessments: Eric Dibble, Ph.D., assistant professor of fisheries ecology, Department of Wildlife & Fisheries, Mississippi State University, Mississippi State, MS

Water Quality, Plankton & Benthic Invertebrate Assessments: A. Scott McNaught, Ph.D., director, Michigan Water Research Center, and assistant professor of biology, Central Michigan University, Mt. Pleasant, MI


Study Sponsors:
* U.S. Army Corps of Engineers Aquatic Plant Control Research Program, Vicksburg, MS
http://www.wes.army.mil/el/aqua
* Aquatic Ecosystem Restoration Foundation, Lansing, MI
http://www.aquatics.org
* SePRO Corporation, Carmel, IN
http://www.sepro.com/index.html
* Cygnet Enterprises Inc., Flint, MI
http://www.gloryroad.net/~aquan/
* Crystal Lake-Perch Lake Property Owners Association


For More Information:
Douglas Genee, chair, Lake Preservation Committee, Crystal Lake-Perch Lake Property Owners Association (Phone: 517-937-6262; e-mail: genee@absolute-net.com)