News & Resources


Summer Spotlight: Effectiveness of Weevils on Eurasian Watermilfoil in Manistee Lake

May 23, 2014

Throughout April and May, we'll be releasing our 'Summer Spotlight' series featuring the research projects and teams that will be tackling some of the big questions in conservation and restoration in Northern Michigan and around the country. 


On a summer day in 1996, the Au Sable ‘Limnology’ course set out in their pontoon boat, equipment in hand, ready for another day of sampling local lakes to understand their ecology.  Fast forward almost 20 years. What the class discovered that day in 1996 is still an on-going issue and the subject of an Au Sable research project this summer.

Eurasian watermilfoil (Myriophyllum spicatum) is an aquatic macrophyte introduced to the US most likely in the 1940s. Once introduced, it lake-hopped its way across North America, taking root in lake bottoms and growing towards the sunlight above. When the Au Sable ‘Limnology’ course discovered its presence in Manistee Lake, it had found a susceptible place to invade. Manistee Lake is shallow. Only 12 feet deep at its highest point, sunlight is at a premium. As a result, Eurasian milfoil was able to spread throughout the entire lake as a dense mat, taking up space as well as depleting oxygen when the plants decompose. Today, the lake ecosystem suffers as a result and the heavy milfoil presence makes recreational activities on the lake a challenge.

In 1998, the Manistee Lake Association believed it had found a viable solution. A native Milfoil Weevil (Euhrychiopsis lecontei) had been identified that could help to suppress the invasive Watermilfoil. Even when introduced, there were questions about the long-term viability of this proposal.  For instance, when the weevils suppressed the Watermilfoil, would the weevil population decline as well with the loss of their food source, making it possible for the Watermilfoil to return? If so, how often do more weevils need to be introduced to continue suppress the Watermilfoil?

Au Sable Research Role

The Au Sable Research Team is taking up these questions. The team collect Watermilfoil samples from the lake and analyze them for weevils and any weevil damage to the plant. The data will contribute to a larger dataset started by Au Sable professor, John Korstad, in 1998 to understand the fluctuating weevil and Watermilfoil population. The results will also inform the Manistee Lake Association about how weevils are working as a biocontrol method so they can take proper action to protect their lake.

Meet the Team

Colten Wolfe attends Oral Roberts University, where he is majoring in Environmental Sustainability with minors in Chemistry and Biology. He is excited to take part in research of the effect of aquatic weevils on the vegetation of Lake Manistee. In conjunction with his research, Colten will also be taking courses in Aquatic Biology and Lake Ecology and Management during the summer. At ORU, he is involved in the Green Club, which spurs initiatives for a more environmentally sustainable campus. Colten loves to be outside enjoying God's creation while hunting, fishing, and camping.

Nathan Goelzer is entering his senior year at Oral Roberts University (ORU) where he is majoring in Biology with a minor in Biochemistry. Nathan will be part of the research team exploring the effects of aquatic weevils on the vegetation on the Manistee Lake. He will also be taking the Aquatic Biology and Lake Ecology and Management courses through the Institute this summer. Currently, Nathan is involved in a research project surveying aquatic macroinvertebrates in Fred Creek, which flows through the ORU campus. Nathan has strong connections to the Western US, originating from California and also having lived in Texas and Arizona. He is an Eagle Scout and has enjoyed canoeing the backwaters of Canada and hiking in Yosemite National Park. He also enjoys camping, fishing, and competitive shotgun shooting.