Eurasian Watermilfoil: Status and Management in Iowa

In 1993, Eurasian watermilfoil (Myriophyllum spicatum L.) was discovered in Crystal Lake, Hancock County, Iowa. During the next three years, new infestations were discovered by the Iowa Department of Natural Resources (IDNR) fisheries personnel in four Iowa lakes. In July 1996, a program was established by the IDNR to address the threat posed by Eurasian watermilfoil to Iowa\u27s aquatic ecosystems. As part of the Eurasian Watermilfoil Program, statewide aquatic vegetation monitoring was begun to identify those lakes currently infested with Eurasian watermilfoil. Monitoring activities were conducted by IDNR field technicians during the summers of 1996 through 2000. During this time period, 366 surveys of 290 waterbodies were conducted. These surveys resulted in the identification of 11 infested lakes located in eight counties. Following identification of an Eurasian watermilfoil infestation, management plans were prepared for each identified waterbody and prescribed management activities were implemented. These activities included posting Eurasian watermilfoil signs, mapping existing Eurasian watermilfoil beds, surveying the waterbody to determine the abundance and diversity of native aquatic macrophytes, determining lake water volume, and surveying the waterbody for threatened and endangered aquatic plant species. Boating restrictions were also implemented if warranted. As a result of the management plan review process, chemical treatment was determined to be the most suitable management practice for all waterbodies identified as infested with Eurasian watermilfoil. Chemical treatment was accomplished primarily through the use of the aquatic herbicide fluridone (Sonar). Complete eradicat10n appears to have been achieved for seven of the 16 identified infestations