The aquatic herbicide fluridone (trade name Sonar() has been shown to be an effective herbicide that controls many aquatic plants including the submersed exotic weed, Eurasian water milfoil (Myriophyllum spicatum). The liquid formulation of this herbicide, the only formulation currently used in Michigan, was first used in the state to control aquatic weeds in 1987. It is a broad spectrum, systemic herbicide that effectively disperses throughout the water column. However, there has been little agreement on the appropriate uses and application rates of Sonar( in Michigan despite nearly a decade of evaluation and attempts to reach consensus amongst the various stakeholders. On October 14,1998, the Michigan Environmental Science Board (MESB) was requested by Governor John Engler to review the research and evaluate seven preliminary conclusions reached by the Michigan Department of Environmental Quality (MDEQ), regarding the efficacy of the herbicide, Sonar(. MDEQ has regulatory authority over the use of herbicides to control nuisance aquatic plants and issues permits for the use of such chemicals.
A Panel of scientists was formed to address the Governor's charge to the MESB. Dr. Bette J. Premo (aquatic ecology, White Water Associates, Inc.) chaired the Panel, which consisted of Dr. Ted R. Batterson (aquatic ecology, Michigan State University); Dr. John A. Gracki (chemistry, Grand Valley State University); Dr. Clarence D. McNabb (aquatic ecology, Michigan State University); and Mr. Keith G. Harrison (ecology, Michigan Environmental Science Board).
The investigation consisted of the accumulation and evaluation of peer-reviewed and some non-peer-reviewed literature and data on the subject. In addition, oral and written testimony from experts, industry specialists, state regulatory agencies, environmental organizations, and concerned citizens was also considered. Ultimately, a 96-plus page report was prepared by the MESB Panel that was submitted to Governor Engler in October 1999. That document is entitled "Evaluation of the Use of Sonar( in Michigan" and can be obtained from the MESB in Lansing, Michigan (e-mail: mesb@state.mi.us; telephone: 517-373-4960; fax: 517-373-6492). It is also available electronically at MESB's Web site (http://www.mesb.org/pubs/ss/ss.html).
In turn, the report was submitted to Mr. Russell Harding, Director of the MDEQ on October 13,1999. Ms. Diana Klemans, Chief of MDEQ's Inland Lakes and Wetlands Unit of the Land and Water Division, the unit responsible for issuing aquatic herbicide permits, has indicated that MDEQ agrees with the conclusions and recommendations of the Panel (see below). She reports that they will soon initiate the administrative rules process to define allowable uses of the liquid formulation of Sonar( in Michigan water bodies and are modifying their interim strategy for Sonar( use in Michigan for the year 2000. The interim strategy will incorporate some of the Panel's recommendations, e.g., a treatment concentration of six ppb Sonar( followed by a potential retreatment boosting the concentration back up to six ppb.
The conclusions and recommendations that were reached by the MESB Panel regarding MDEQ's preliminary conclusions are presented below. They are taken verbatim from the Panel's report.
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MDEQ Conclusion 1. A balanced, diverse aquatic plant community should be maintained in all water bodies for the maintenance of Healthy fish and wildlife populations.
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In general, the MESB Panel concurs with MDEQ Conclusion 1; however, history has demonstrated that aquatic ecosystems that are managed by humans using Sonar( or other means are likely to be never in balance. Given this, the MESB Panel recommends that Conclusion 1 be modified by omitting the word, balance.
MDEQ Conclusion 2. Sonar( should not be used in Michigan at or near the labeled rate to eliminate all or the majority of aquatic plants in a water body.
The purpose of the use of Sonar( is to rehabilitate water bodies that have become overpopulated with Eurasian water milfoil. The process necessarily entails that such removal be accomplished in a manner that will not negatively impact the more desirable native species but, rather, encourage their proliferation and resurgence of dominance within the water body. Based on the available research, Sonar( application rates at or near the label rate will remove Eurasian water milfoil; however, at these rates, it will also impact significantly the native species. Removal of all or the majority of the aquatic species (Eurasian water milfoil and the native species) from a water body would be a component of a comprehensive lake restoration project, which is not the purpose of the MDEQ program. Therefore, the MESB Panel concurs with MDEQ Conclusion 2.
MDEQ Conclusion 3. When Sonar(r) is used to control Eurasian water milfoil, negative impacts on native aquatic plants should be minimal in the year of treatment and in subsequent years.
The MESB Panel concurs with MDEQ Conclusion 3 but suggests that the option for rehabilitation of a given water body may be not only to control, but also totally eliminate Eurasian water milfoil by the application of Sonar(r). Implementing this option may, in the year of treatment, have a greater than minimum negative impact on native aquatic plants. Eliminating by administrative rule the option to eradicate Eurasian water milfoil when conclusive data to condemn or promote this particular approach are not yet available, may be premature. Because of this, the MESB Panel suggests that Conclusion 3 be qualified to allow the option to use Sonar(r) in Eurasian water milfoil elimination and water body rehabilitation programs, and that such use be allowed at the MDEQ's discretion on a case by case basis with decisions based on its review of the available scientific field studies and specific physical, limnological, and biological data for the particular water body in question.
MDEQ Conclusion 4. The Sonar(r) concentration that effectively controls Eurasian water milfoil with minimal impacts on native species, is between five and eight parts per billion (ppb).
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