Invasive Species

Overview

One of the most aggressive and noxious invasive species of aquatic weed found in North American lakes, Eurasian watermilfoil (EWM), has established itself in Lake Leelanau. This determination was confirmed conclusively earlier this month by Brian Price, biologist for the Lake Leelanau Lake Association and former Executive Director of the Leelanau Conservancy, and Jeff Sanborn, immediate past president of the Lake Leelanau Lake Association (LLLA).

Eurasian watermilfoil is a rooted, submerged aquatic plant which grows in water from two to 30 feet deep, but most commonly in Lake Leelanau at depths of 8-12 feet. It prefers still or slow-moving water and is considered to be a highly invasive species. Although a complete survey documenting the extent of the infestation in both the northern and southern portions of Lake Leelanau has not yet been completed, a preliminary drone survey suggests that the largest infestation is along the east shore of South Lake Leelanau and a smaller infestation on the south side of the Narrows.  As yet, we have not found EWM in North Lake Leelanau. 

This brief plan describes the nature of the threat and suggests steps which could be taken in the short and long term to control it.

Eurasian Watermilfoil

Eurasian watermilfoil (Myriophyllum spicatum or spiked watermilfoil) is native to Europe, Asia, and North Africa, but has a wide geographic and climatic distribution among some 57 countries, extending from northern Canada to South Africa. Eurasian watermilfoil is known to hybridize with the native northern watermilfoil (M. sibiricum) and the hybrid has also become invasive in North America. This hybridization has been observed across the upper midwestern United States (Indiana, Minnesota, Michigan, Wisconsin) and in the Northwest (Idaho, Washington).

By obstructing water‐based recreation and decreasing a lake’s aesthetic value, infestations of EWM can also lead to a decline in lakefront property value (Eiswerth et al. 2000, Horsch and Lewis 2009, Zhang and Boyle 2010).

EWM was likely first introduced to North America in the 1940s, and is now found across most of Northern America, including a number of lakes in Michigan. The plant is now established in Crystal Lake, Duck Lake, Higgins Lake, Houghton Lake, Long Lake, Paradise Lake, Portage Lake, and Walloon Lake, among others. It is recognized as a serious threat by Michigan’s Department of Natural Resources.

Impact

In lakes or other aquatic areas where native aquatic plants are not well established, the Eurasian plant can spread quickly. It has been known to crowd out native plants and create dense mats that interfere with recreational activity, including boating, fishing and swimming. Left unchecked the plant can grow so densely that it can render some lakes virtually unnavigable, seriously affecting property values. By blocking out sunlight to native aquatic plants and preventing them from photosynthesizing, the plant can create zones where the amount of dissolved oxygen is sufficiently depleted that the levels are detrimental or fatal to aerobic organisms. Eurasian watermilfoil grows primarily from broken off stems, known as shoot fragments, which increases the rate at which the plant can spread and grow. Once established, the course of the infestation in any given lake will be affected by variables such as suitable water depths and substrate, along with water temperature and clarity.

Means of Control

Although biological and chemical control of Eurasian watermilfoil have been employed extensively since roughly 2000, hand-harvesting of invasive milfoils has shown much success as a management technique and is the strategy we recommend adopting to control Eurasian watermilfoil in Lake Leelanau. Several organizations in the New England states have undertaken large scale, lake-wide hand-harvesting management programs with extremely successful results. In northern Michigan, Higgins Lake has extensive experience with Diver Assisted Suction Harvesting (DASH) over the past decade.

Unfortunately, it is virtually impossible to completely eradicate the species once it is established. As a result, regular maintenance must be done once an infestation has been reduced to affordably controlled levels. Well trained divers with proper techniques have been able to effectively control and then maintain many lakes, especially in the Adirondack Park in northern New York where chemicals, mechanical harvesters, and other disruptive and largely unsuccessful management techniques are banned. After only three years of hand harvesting in Saranac Lake, the program was able to reduce the amount harvested from more than 18 tons to just 800 pounds per year. 

Biological controls have been tried widely with limited success. The water veneer moth, an aquatic insect, feeds upon and damages this watermilfoil. It has been used as an agent of biological pest control against the milfoil in North America. The milfoil weevil has also been used as biocontrol.   Similarly, chemical control has been deployed where infestations are severe, but hand harvesting appears to be the more cost effective and successful strategy with fewer potential side effects for the ecosystem.

Action Plan

A compelling case can be made for acting yet this year, within weeks of discovering the extent of the infestation, particularly in high traffic areas of Lake Leelanau.  Preventing boat traffic from spreading plant fragments, and not allowing EWM to spread into North Lake Leelanau, is a top priority.

To summarize, the most successful means of control appears to be hand harvesting, which requires using trained divers to dig up the plants by their roots. The plants are then fed by the divers into an underwater suction tube, drawing the plant out of the water and into a boat.  The plants are collected in mesh bags, then composted or sent to a landfill.

Since control operations will disturb bottom sediments, a permit from the State of Michigan is required to begin control operations.  We have been in contact with permitting authorities, and while we are told that the state estimates 60-90 days to process a new application, we are hopeful that operations may begin late summer or fall. 

Brian Price has had preliminary conversations with contractors who can provide equipment and divers to begin operations on Lake Leelanau.  We have had initial discussions with two providers of DASH boats and gear, one located in Lancaster, NY and one located in Fairview, MI.  Each has given an informal quote over the phone of around $25,000 to buy the needed equipment.  The Michigan manufacturer, based in Fairview, builds boats and also provides equipment to a diver/contractor named Mike Smith.  Smith has extensive experience and has worked for lakes, private owners, and for the State of Michigan at its own harbor facilities.  His services include helping clients obtain permits.  His rate for operating his DASH boat is for harvesting Eurasian watermilfoil on a contract basis $1,300/day.   

2019-2020 Remediation Plan

Assuming we can obtain an expedited permit from the State of Michigan, we estimate the total cost of mounting a remediation program in 2019 to be approximately $35,000, depending on how quickly we can obtain a permit and the remaining available work days this season. Harvesting can occur through September and into October.

Any funds raised but unspent in 2019 will be earmarked for milfoil harvesting and control programs next year. The components of the program are:

  • Estimate for cost of drone and boat surveys of North and South Lake Leelanau to determine the locations and extent of Eurasian watermilfoil infestation: $5,000
  • Estimate to engage contractor to hand harvest milfoil in 2019: $25,000
  • Grant writer to apply for State funds for 2020 milfoil remediation plan: $5,000

            Total estimate 2019 program: $35,000

If operations start this year, we should be able to reduce the spread of the infestation while at the same time gaining valuable experience that will help us focus on removing EWM using the DASH system in the largest infestation in South Lake Leelanau.  Following field operations, we recommend public education measures and developing long term remediation plans, such as the installation of boat washing stations at boat launch sites around Lake Leelanau. A preliminary estimate of the cost of the components of the 2020 program:

  • Continuation of hand harvesting program: $50,000
  • Communication, education and signage: $10,000
  • Estimate for local funds needed to match State funds for boat washing stations: $40,000

            Total estimate of 2020 program: $100,000

Future Remediation Work

The State of Michigan offers grants to organizations like LLLA to undertake control programs for major invasive species, including the installation of preventative measures like boat washing stations. LLLA intends to apply for state funds to help pay for future remediation efforts, but even if granted, such funds are unlikely to cover the entire cost of a comprehensive control program.

The Lake Leelanau Lake Association

The Lake Leelanau Lake Association (LLLA) has an annual operating budget of approximately $60,000. Of this amount, dues from membership provide income of approximately $40,000. The balance of the Association’s income is derived from grants and gifts. The Association’s current level of income is inadequate to fully compensate Brian Price, the Association’s lake biologist, for the considerable time he devotes to monitoring and maintaining the lake’s health. With the exception of Brian Price, all of the organization’s work is done by volunteers.

The Association is a registered (501) (c) (3) nonprofit. Contributions are tax deductible.

We strongly encourage you to contribute to the Lake Leelanau Lake Association to help cover the immediate launch of a concerted effort to control the infestation of Eurasion watermilfoil in Lake Leelanau. While the Association will be applying for State funds to help finance remediation efforts, should we be successful, these funds will not be available until sometime in 2020 at the earliest.

Please send your contribution to:

Kathy Birney, Vice President and Treasurer

Lake Leelanau Lake Association

PO Box 123

Leland, MI 49654

Note: The above information was assembled from online sources and phone interviews.