Bear Lake, Manistee County, MI

Bear Lake Improvement Board, Bear Lake, Michigan

Before Treatment
After Treatment

Bear Lake is a 1,784 acre lake located in sections 4 – 6 of Bear Lake Township, (T.23N, R.15W) and sections 28 – 29, and 31 – 33 of Pleasanton Township (T.24N, R.15W) in Manistee County, Michigan. During the original feasibility study in 2007, Bear Lake was infested with approximately 330 acres of Eurasian Watermilfoil that was concentrated around the west and south portions of the lake, and in the two smaller bays. During the spring of 2008, approximately 163 acres of Eurasian Watermilfoil was located and treated with the systemic aquatic herbicide 2,4-D in offshore areas and with the systemic herbicide Triclopyr in nearshore bay areas on 12 June, 2008 as permitted by the Michigan Department of Natural Resources and Environment (MDNRE). An additional 60 acres of Eurasian Watermilfoil that germinated later in the season (July) was treated with the systemic herbicide 2,4-D on 16 July, 2008 in order to stop further spread of the plant through the growing season. During the fall 2008 grid survey, it was estimated that approximately 126 acres of semi-viable Eurasian Watermilfoil were found (7.4% of the total 1,800 acres containing EWM); however, the results of the June, 2009 grid survey which assessed 558 GPS grid points demonstrated that only 11 acres of Eurasian Watermilfoil infested Bear Lake. These areas included a 7-acre bed located at the southwest portion of the lake as well as the west and east bays. The two bays were successfully treated with Triclopyr due to shallow well restrictions and the southwest portion of the lake with granular 2,4-D. Surveys conducted in spring and late summer of 2010 found approximately 3 acres in the south basin and east bay and 5 acres in the southwest basin which was treated with Renovate OTF and 2,4-D, respectively. A follow-up grid survey in early September revealed that nearly all of the previously treated Eurasian Watermilfoil had died and no new growth has been located. The native pondweed population has flourished throughout the bays and in the main portion of the lake. In particular, species such as White-stem Pondweed (Potamogeton praelongus), Illinois Pondweed (Potamogeton illinoensis), and Small-Leaf Pondweed (Potamogeton pusillus) have expanded in areas previously dominated by the exotic Eurasian Watermilfoil. Additionally, a new species of native dicot (Water Marigold; Bidens beckii) was discovered in the east bay and has replaced Eurasian Watermilfoil in many areas within the bay. Currently, Bear Lake continues to be properly balanced with no viable milfoil and a diverse native aquatic vegetation community.