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Higgins Lake: the benefits of early intervention, community participation, and persistence in controlling Eurasian watermilfoil
Higgins Lake is a 9,900-acre oligotrophic lake located in Roscommon County. The lake, 140 feet at its deepest point, is a tremendous natural resource, attracting thousands of people to live near it near it  and thousands more to visit. Thus, its importance to the region’s economy is unparalleled.
Eurasian watermilfoil (Myriophyllum spicatum) is an invasive exotic species with the potential to disrupt a lake’s ecological system and interfere with recreation. It is generally thought to have first entered lakes in North America in the 1940s. EWM is a concern because t rapidly colonizes lakes and spreads easily by fragmentation. This plant can grow up to the surface of the water and form extremely dense mats, inhibiting boating and swimming. It also crowds out some of the more ecologically beneficial aquatic plants. Once established, Eurasian watermilfoil is very difficult to remove and can be spread from lake to lake by boat traffic.
During the period of June 2001 through December 2002 local citizens, organizations, and resource agencies were involved with developing a watershed management plan for Higgins Lake. As an outgrowth of that project, the Higgins Lake Foundation funded an assessment of Eurasian watermilfoil (EWM), which was conducted late June/early July of 2002 by Huron Pines and repeated by August 2003. The study was conducted in order to identify major EWM weed beds in the lake, characterize the extent of the problem, and provide baseline information for analysis of future management options.
With its sandy substrate and low nutrient levels, Higgins is not s susceptible to colonization of EWM as many other lakes in Michigan. However, with three public (DNR) boat launches, two private marinas and 78 road-ends, there are numerous opportunities for the introduction of EWM and other exotic species. Since many lakes in the region already have significant problems with Eurasian watermilfoil, it seems likely that plant fragments are spread from one lake to another by watercraft.
As a result of the EWM survey, nearly 100 locations of Eurasian watermilfoil were identified within Higgins Lake. A few of the larger (for Higgins, greater than 1,000 square feet) weed beds were found between the shore and the drop-off. For the most part, however, the few significant areas of EWM infestation were generally in long, narrow bands along the drop-off. While the EWM survey was not intended to document every individual plant in the lake, many of the locations are areas where only a few sprigs of EWM have taken hold. Some of these “minor” sites are in the area between the shore and drop-off, but most are located close to the shore, particularly near docks/boat hoists. Due to the fact that EWM can take hold quickly, addressing these small areas of plant growth is essential to the successful control of EWM in Higgins Lake.
 The key to effective control of Eurasian watermilfoil in Higgins Lake is to think in terms of the long-term management of the lake. The course of action should be realistic, cost-effective, and ecologically sound. Due to the unique characteristics of Higgins Lake and the fact that the EWM problem is in its early stages, Huron Pines staff recommend an integrated management program tailored specifically to Higgins Lake. The involvement and support of community organizations and residents around the lake has made such an approach possible. The strategy, employed one small site at a time, is designed for the long-term health of the Higgins Lake ecosystem, keeping costs – both financial and ecological – to a minimum.
Control options for exotic species can be, in general, lumped into three categories. These include: 1) Biological control,
2) Chemical treatment, and 3) Physical control.
Biological control methods, specifically predation of the plant by an aquatic weevil (Euhrychiopsis lecontei), have had initial success on some northern Michigan lakes. This method of control can be expensive initially and time is needed to tell how well a weevil population will sustain itself and provide long-term control; however, this may well prove to be the most effective treatment over time. In the summer of 2002, while collecting some plant samples, biologists with the US Army Corps of Engineers were able to find these herbivores already in Higgins Lake. A population estimate, along with a characterization of their recent impact on EWM in the lake, cannot be determined without further study.
The use of herbicides to treat a lake is a very expensive approach that often causes concern because of the immediate effect of the application on non-targeted species, the fact that long-term impacts on all organisms are poorly understood, treatments will likely need to be repeated in future years, and there is a high potential for re-infestation. Because of the early stage of the problem in Higgins Lake and its high volume of water, widespread chemical treatment is not an appropriate method of control. Limited use of an herbicide for spot treatment at the three DNR Boat Launch sites is used and a couple of additional sites are proposed for 2008.
Physical control, such as the use of a light barrier on the lake bottom, has also been used to control EWM. This is an ecologically sound, low-cost method for small problem areas, although it is labor intensive to install and can be difficult to maintain. By blocking out sunlight, EWM (and everything else) is prevented from growing. It is recommended that benthic barriers be installed at already-identified problem sites (small to moderate in size) early in the season.
 This treatment is being used effectively at several locations in the lake. The material, a geo-textile fabric held in place by stakes and a small amount of rock, was cut into 15’ by 30’ panels for ease of installation by a 4-person team of scuba divers. While the fabric is somewhat permeable, the fabric did need some holes cut into it to allow the escape of gas from bottom sediments. A volunteer group of local scuba divers are making this treatment a success.
The other form of physical control of EWM, plant harvesting, refers to both pulling the plant by hand as well as using a machine. Because fragmentation of EWM leads to its spread, mechanical harvesting is not a viable option for Higgins Lake. The hand harvesting experience of those involved with the Higgins Lake Project is that this method may be the best technique for control of very small (less than 25 square feet) patches. Garden-style rakes seem to the most effective tool to aid in removing the plant. Great care must be taken so as to minimize plant fragmentation. Those removing the plants should ensure that plant fragments are collected in the work area and that plants are disposed of off site. This method is very labor intensive and will need to be repeated several times. Year by year, property owners should notice a gradual reduction in the size of the EWM weed bed they are working on.
Huron Pines currently maintains a database of property owners around the lake with Eurasian watermilfoil. Of the approximately 1,100 parcels along the lake, 30 have been identified where EWM is taking hold near the shoreline. Lakefront property owners could carefully remove these plants. EWM can be difficult to identify, so property owners interested in removing the exotic plant will need to learn to distinguish it from other plants growing in Higgins Lake. In the summer of 2003, the Higgins Lake Property Owner’s Association mailed EWM ID cards to all lakefront property owners to help with this effort. In upcoming years, it will be important to also involve other lake users in the effort to limit the opportunity for EWM growth.
Because EWM has been documented early on in its infestation of the lake, there is a great opportunity to use a hybrid method of biological control, limited use of chemicals, education, and physical control techniques (and a little persistence) to severely limit the spread of the invasive plant.
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