The LMCD’s harvesting program was initiated in 1989. At that time, harvesting was a reasonable solution
for mitigating the impacts of milfoil, as other feasible options did not exist. The objective of the
harvesting program is to provide navigation by cutting channels and clear-cutting other areas (the
machines cut milfoil about 4-feet below the water surface).
After 23 years, we are not aware that any program review or evaluation has been conducted of the
harvesting program.
The harvesting operation commences in mid- to late-June and ends in mid-August. However, the boating
season peaks around the Fourth of July, then declines – this offset is problematic because many areas do
not receive relief until too late in the season.
The harvesters generate milfoil fragments, which wash to shore and become a maintenance headache for
lakeshore owners (we know milfoil fragments are generated in other ways, but the harvesters add
significantly to this). Fragments also sprout new milfoil plants.
The harvesters are owned and operated by the LMCD. This is a substantial capital asset, which commits
the LMCD to this method and thereby reduces the overall program flexibility.
The purchase of a replacement harvester should be considered only after other methods and
models are considered with competent technical input.
The five bays in the bay-wide milfoil program were chosen because they were among the worst milfoil
areas on Lake Minnetonka. As the harvesters do not now work in these areas, there is substantially less
milfoil remaining to be harvested in the lake. The total treated area in the five bays is over 600 acres,
compared to the typical harvesting totals of 300 to 350 acres.
With fixed annual operational costs of about $100,000 to $105,000 per year (excluding the harvesters’
depreciation) and lower need with five bays removed from the program, either the cost per acre will go up
or less acreage will be required for treatment (or both).
Harvesting is not popular with Lake Minnetonka lakeshore owners. Of the lakeshore owners who
participated in the five-bay herbicide program, 93% preferred the bay-wide herbicide treatments over the
harvesting program (see: www.LakeMinnetonkaForum.com).
Does the LMCD’s harvesting program need a third harvester any longer, given the worst milfoil
areas are now managed under another more successful program?
Flowering rush, another invasive plant, is in Lake Minnetonka. Flowering rush is readily spread by
harvesters (and motorboats). A responsible, conservative approach should include avoiding known
Flowering rush beds, which would further diminish the use of harvesters.
The Pelican River Watershed District ceased the use of harvesters because they spread Flowering
rush throughout the Detroit Lakes Chain. There are no management plans or actions for
Flowering rush on Lake Minnetonka.
There are less costly, safe and more effective options at this time. Harvesting costs about $300 per acre
(excluding depreciation). Contact herbicides (different from those being used in the five bay program, but
the same as are being used by hundreds of lakeshore owners under permit from the MN DNR) would cost
about $250 per acre and have these advantages: a) they can be applied early in the season and last the entire
season (in June, before milfoil surfaces), b) they are applied by professional, licensed commercial
applicators, c) the program is flexible and scalable – if the need is lower, the costs are lower and d) they
can be targeted to the precise areas in the lake to facilitate navigation. This and other options have not
been considered.
Other milfoil control options are cheaper, more flexible, do not require capital investments and
assets and can be implemented earlier in the season.
Harvesting is not typically indicated for lakes like Lake Minnetonka.
“Mechanical harvesting (of Eurasian watermilfoil) provide temporary but fair control in bodies of water
that are small to moderate in size, whereas hand harvesting and suction harvesting provide longer term
control than mechanical harvesting or raking. None of these mechanical methods alone results in longterm
control of Eurasian watermilfoil; as such, these methods should be employed as part of an integrated
weed control strategy.”1
Continuing with the harvesting program at this time is contrary to best management practices, as a) Lake
Minnetonka is a large lake with 3,000 to 5,000 acres of milfoil, b) Hand harvesting and suction harvesting
is very expensive, at least 10-times more than harvesters and c) There is no integrated weed control
strategy for lake Minnetonka.
The Lake Minnetonka Association believes it is ill advised to commit to the continuation of the
milfoil harvesting program in its present form. Before a decision to purchase a third harvester is
made, we recommend:
- A thorough and comprehensive program review and evaluation be made.
- A comprehensive milfoil (and other invasive plant) management plan be developed.
1 Biology and Control of Aquatic Plants: A Best Management Practices Handbook. Aquatic Ecosystem Restoration Foundation, 2009.
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