Washington State Department of Ecology

Aquatic Plant Management - Mechanical Cutting

Description of Method

Mechanical weed cutters cut aquatic plants several feet below the water's surface. Unlike harvesting, cut plants are not collected while the machinery operates. There are two types of underwater weed cutters commercially available, including:

Portable, boat-mounted cutting units
Specialized barge-like cutting machines

Cutting is generally performed during the summer when plants are near the surface.

Portable Boat-mounted Cutters

An electric boat-mounted underwater cutter cuts a four-foot swath up to seven feet below the water's surface. It has been reported that it takes about three hours to clear one acre of plants using this device. The Jenson Lake Mower™ pictured here, starts at about $2,500 and cuts 7-10 hours on a fully charged 12V deep-cycle marine battery. An accompanying five-foot wide boat-mounted rake can remove cuttings or floating plant. A portable underwater cutting unit can be installed on a 14-foot or longer boat.

Specialized Underwater Cutters

Specialized underwater weed cutters can cut weeds in water as shallow as ten inches and as deep as five feet. The main sickle will cut a swath ten feet wide. It has been reported that specialized cutters can cut about 12 acres per day.

Cleanup

Cutting generates floating plants and fragments. It is important to remove all plants and fragments from the water to prevent them from rerooting or drifting onshore. Cleanup can be accomplished using a weed rake. However, specially designed nets should be used when using boat-mounted and larger underwater cutters. The time needed for cleanup depends on the density and types of plants and the amount of acreage cut.

Advantages

Cutting creates immediate open areas of water.
Mechanical underwater cutters can work in shallow waters not accessible to larger harvesters.
Habitat for fish and other organisms is retained if the plants are not cut too short.
Prices of mechanical cutters are substantially lower than harvesters.

Disadvantages

Cutting is similar to mowing a lawn--the plants grow back and will likely need to be cut several times during the growing season.
Some species are difficult to cut.
Cutting creates plant fragments which may enhance the spread of invasive plants such as Eurasian watermilfoil. These fragments may also drift onshore and decompose.

Permits

Mechanical cutting in Washington requires hydraulic approval, obtained from the Department of Fish and Wildlife. For projects costing over $2,500, check with your city or county to see if a shoreline permit is required.

Costs

Portable boat-mounted cutting units cost from $400 to $3,000. Specialized underwater cutters cost about $11,000.

Vendors

The following list of vendors is provided for your information. It is not our intention to endorse or promote specific vendors or products and this list may not be comprehensive. Vendors who wish to be added to this list should contact Kathy Hamel at kham461@ecy.wa.gov.

Please contact the companies directly if you would like more information about their products.

Jenson Lake Mower Jenson Technologies Development Corporation
412 Summer Mountain Drive San Marcos, Texas 78666
Toll Free: (888) 298-5253
Tel. 512-393-5073
Fax 512-393-5074
http://www.lakemower.com (Electric boat-mounted aquatic weed cutter and boat-mounted rake)

The Aquatic Vegetation Groomer is a new underwater cutting tool that was recently developed. Contact Lake Weeders Digest at: http://www.weedersdigest.com

Hockney Underwater Weed cutters
Hockney Co, 913 Cogswell Drive
Silver Lake, WI 53170
(414) 889-4581
http://www.weedcutter.com

Questions about this page? Contact Kathy Hamel by e-mail at kham461@ecy.wa.gov