Aquatic Plant Management - Manual Methods

Description of Methods

Hand-Pulling

Hand-pulling aquatic plants is similar to pulling weeds out of a garden. It involves removing entire plants (leaves, stems, and roots) from the area of concern and disposing of them in an area away from the shoreline. In water less than three feet deep no specialized equipment is required, although a spade, trowel, or long knife may be needed if the sediment is packed or heavy. In deeper water, hand pulling is best accomplished by divers with SCUBA equipment and mesh bags for the collection of plant fragments. Some sites may not be suitable for hand pulling such as areas where deep flocculent sediments may cause a person hand pulling to sink deeply into the sediment. Detailed description of diver hand pulling methods for milfoil removal projects.

Cutting

Cutting differs from hand pulling in that plants are cut and the roots are not removed. Cutting is performed by standing on a dock or on shore and throwing a cutting tool into the water. A non-mechanical aquatic weed cutter is commercially available. Two single-sided stainless steel blades (razor sharp) forming a "V" shape are connected to a handle which is tied to a long rope. The cutter can be thrown about 20 - 30 feet into the water. As the cutter is pulled through the water, it cuts a 48-inch wide swath. Cut plants rise to the surface where they can be removed. The stainless steel blades that form the V are extremely sharp and great care must be taken with this implement. It should be stored in a secure area where children do not have access.

*Case Study from Conesus Lake in New York: "One of the Conesus Lake Association members has used a cutting device with good success for the past several years. Swimming and wading areas around the dock are clear of milfoil. The steps are as follows:

  1. Early spring, when weed growth is first noticed is the best time to start. If early enough in the spring a wet suit or chest waders will be necessary or use this method from the dock. Pick a day when the wind will direct floating cut weeds towards your dock or shore. Be respectful of your neighbors. Remember, cut weeds, if left in the lake, will reseed new plants and leave nutrients in the lake.
  2. Hold firmly on the end of the line and throw the cutter Y legs first. Use a back and forth motion as you retrieve the cutter by tugging on the line. Allow the cutter to settle to the bottom between tugs.
  3. As the cut weeds float to the surface, use two large fish nets to gather them. As one net is full, let the water drain by using the second net.
  4. The cut weeds can be deposited on a cross hatched, wooden lattice or fencing material so they can drain thoroughly (see also the case study for raking below).
  5. When drained sufficiently, use a pitchfork to place the semi-dry weeds into plastic bags for use as garden mulch or for disposal. It is impractical to try and burn the weeds since too much time is required for complete drying.

Based on several year's experience with this weed control method, the results will be acceptable if the process is repeated every other week or two. Over time the regrowth of the weeds becomes less of a challenge".

Raking

A sturdy rake makes a useful tool for removing aquatic plants. Attaching a rope to the rake allows removal of a greater area of weeds. Raking literally tears plants from the sediment, breaking some plants off and removing some roots as well. Specially designed aquatic plant rakes are available. Rakes can be equipped with floats to allow easier plant and fragment collection. The operator should pull towards the shore because a substantial weight of material can be collected in a short distance.

*Case Study from Conesus Lake in New York: "One of the Conesus Lake Association members has used a weed rake with great success for the past several years. Swimming and wading areas around the dock are clear of weeds. The process is the same that can applied to the use of any weed rake regardless of design or model. The steps are as follows:

  1. Early spring, when weed growth is first noticed is the best time to start. If early enough in the spring, a wet suit or chest waders will be necessary. Pick a day when the wind will direct floating weeds toward your dock or the shore. Be respectful of your neighbors. Remember, weeds, if left in the lake, will reseed new plants and leave nutrients in the lake!
  2. Use a back and forth motion with the rake, much as you would with a vacuum cleaner.
  3. As the weeds float to the surface, use two large fish nets to gather them. As one net is full, let the water drain by using the second net. Once drained, the weeds can be deposited in a large trash container lined with a plastic bag.
  4. Place an old window screen or a framed screen on top of the trash can and move the can to a place where it can sit for a while. Invert the trash can over a couple of 2 x 2's or some like means to prop up the screened area allowing water to drain out through the screen over time.
  5. After a few days, the remaining weeds will be light, compacted, and ready for disposal and pickup by garbage collection. Or, if desired, the weeds can be mulched and used in gardens for fertilizer. It is impractical to try to burn the weeds since too much time is required for complete drying.

Based on several year's experience with this weed control method--- and a process that was repeated every week or two --- this Conesus Lake member has been very pleased with the results. He reported that the growth of weeds slows down over time. This may be due to the back and forth movement of the rake".

Cleanup

These methods create plant fragments. It's important to remove all fragments from the water to prevent them from rerooting or drifting onshore. Plants and fragments can be composted or added directly to a garden.

Advantages

Disadvantages

Permits

Permits are required for many types of projects in lakes and streams. Check with your city or county before proceeding with your project. The Washington State Department of Fish and Wildlife requires a permit called an Hydraulic Project Approval for all activities taking place in the water including hand pulling, raking, and cutting of aquatic plants.

Costs

Costs will vary based on the size and location of the project. Hand-pulling costs up to $130 for the average waterfront lot for a hired commercial puller. A commercial weed cutter costs about $130 with accessories. A commercial rake costs about $95 to $125. A homemade weed rake costs about $85 (asphalt rake is about $75 and the rope costs 35-75 cents per foot).

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

http://www.bartswatersports.com/catalog.asp?C=27

http://www.stoneycreekequip.com/form/weedrake.htm

http://weedersdigest.com

http//www.aquatic-weedinator.com

https://www.lakemower.com (boat-mounted aquatic weed rake)

http://www.weedrazers.com

http://www.tweedertool.com

* The Conesus Lake Association, Inc. in Lakeville, New York has graciously allowed Ecology to reproduce some case studies of the use of these methods on our website. These excerpts are from "The Conesus Lake Dockside/Near-Shore Lake Weed and Algae Treatment Guide" 2002 Edition. Price $8.00.

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