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Mechanical Treatment

What is Mechanical Treatment?

Mechanical Treatment is the physical removal of the plant or making it physically impossible for the plant to live in the conditions it is presented with. This can involve pulling plants by hand, mowing, or creating conditions where the plant is unable to photosynthesize.

Mechanical treatments can be labor intensive and unpractical in larger bodies of water and in some cases mechanical methods may make the problem worse than it previously was. As with any treatment there are pro’s and con’s and those are noted for each type of mechanical treatment.
 

Cutting, Mowing or Hand Removal

Cutting, mowing or hand removal is removal of the plant from the body of water. It is generally done with a modified rake or boom that can be dragged through the water to gather up the vegetation. Rooted vegetation needs to be pulled from the bottom or cut at the base.
 
PROS:
It is relatively inexpensive and doesn't require the use of chemicals.
 
CONS:
Very labor-intensive and impractical for larger bodies of water. It may also make the problem worse due to fragmentation, where any part of the leafy portion of the plant that is left in the water can grow a new plant. Also, disturbance of the substrate makes it difficult to remove all the plants in one pass, making multiple attempts necessary. It is unlikely to work in large pond due to the amount of vegetation that needs to be removed. It can be useful in selectied areas such as around docks and swimming areas.
 

Dyes or Fertilization

Dyes or Fertilization are mechanical techniques that are designed to limit the ability of sunlight to penetrate into the water.
 
Dyes (Aquashade*, Black Pond DyeMond*, or AquaDye*) are products that will change the color of the pond (black or blue, depending on the product) limiting sunlight penetration. The best time to apply a dye is in the spring prior to the period when plants begin to grow.
 
* Information listed is not intended as a product endorsement. Similar products may be available.
 
An Illustration of how dyes work to prevent vegetation growth in ponds.

Fertilization involves the process of increasing phytoplankton (small microscopic plants; also called planktonic algae) to limit the sunlight penetration. In order to fertilize the pond, a rate of 1 pound of nitrogen, 2 pounds of phosphorus and 1 pound of potash per surface acre (best obtained by using liquid 9-18-9 fertilizer).  This liquid fertilizer should be diluted by half and spread evenly across the surface of the pond beginning in mid-April (water temperature 60°F - 65°F) and continuing every two weeks until mid-June. For more information on fertilizing a pond, please see the Water Quality section.
 
PROS:
Dyes and fertilization are relatively inexpensive and some may find that they like the color of dyed pond water. Both methods are nontoxic and should not have a negative effect on pond life.
 
CONS:
The color of the pond may look unnatural to some and the dyes are a chemical that is added to the water. Fertilizer can increase the chance of a low oxygen kill in the heat of the summer months. Ponds with larger inflows will require more dye/fertilizer or repeated applications due to replacement with untreated water. Even with treatment, light can still penetrate into shallow areas allowing plants to grow in these areas. The shading can limit the amount of plankton growth, which will limit fish production.
 

Barriers

Barriers are PVC, fiberglass or nylon material placed on the bottom of the pond and designed to block sunlight and compress plants thereby preventing their growth.
 
PROS:
Barriers are relatively inexpensive and no chemicals are added to the pond.
 
CONS:
Barriers are impractical for larger ponds and must be cleaned of debris on a regular basis to prevent new vegetation growth on top of barrier. Barriers can also affect macroinverterbrates living in sediments, which may in turn affect fish production.
 
 
Mechanical Control quick reference
Plants respond differently to various control measures. The first step is determining which plant you have. Please refer to the Plant Identification portion of this website to identify the plant and see what control measures will work best on your plant, Use the chart below for a quick guide. Each plant type is rated on its effectiveness (E = Excellent, G = Good, F = Fair, P = Poor, Blank = Ineffective).
 
 

 

Mechanical Control 

 

Cutting or Raking

Dyes or Fertilization

Barriers

Algaes

 

 

Chara

F

F

G

 

Filamentous Algae

G

F

F

 

Planktonic Algae

 P

 

Non-Rooted Floating Vegetation

 

 

Bladderwort

F

 

 

 

Duckweed

F

 

 

 

Mosquito Fern

F

 

 

 

Water Hyacinth

F

 

 

 

Watermeal

P

 

 

Rooted Floating Vegetation

 

 

Lotus

P

 

 

 

Spatterdock

P

 

 

 

Watershield

P

 

 

 

White Lilly

P

 

 

Submerged Vegetation

 

 

Coontail

F

F

G

 

Elodea

F

F

G

 

Floating Pondweeds

F

F

G

 

Hydrilla

F

F

G

 

Mud Plantain

F

F

G

 

Naiad

F

F

G

 

Submerged Pondweeds

F

F

G

 

Vallisneria

F

F

G

 

Watermilfoil

F

F

G

Emergent Vegetation

 

 

 

 

Alligator Weed

F

 

 

 

Arrowhead

F

 

 

 

Bulrush

G

 

 

 

Cattail

F

 

 

 

Common Buttonbush

F

 

 

 

Creeping Water Primrose

F

 

 

 

Giant Reed

F

 

 

 

Horsetail

F

 

 

 

Lizard's Tail

F

 

 

 

Sedges

F

 

 

 

Smartweeds

F

 

 

 

Spikerush

F

 

 

 

Water Willow

F

 

 

 

Willow

F

 

 
 
 

Other Methods

There are a few other methods for mechanical removal of aquatic vegetation from a pond. They include methods such as booming vegetation or algae off of the surface of the pond, and draw-downs.
 
Booming is basically skimming the floating vegetation off of the surface of the pond by use of a floating rope stretched across the pond, floating wooden boards tied with rope across the pond of using a pool skimmer or other nets to capture the vegetation. This method is fairly easy to use, and inexpensive. However, if there are any particles of the plant left behind, it may be ineffective for long-term control. In ponds with large outbreaks of duckweed or watermeal, this method will effectively remove portions of the vegetative mass, but plants left behind will quickly reestablish back to problem status.
 
Draw-downs can be incredibly effective on specific types of plants if a healthy freeze is accomplished.  This is a technique normally used in more Northern states, where freezes are severe and prolonged. It involves pumping water out of the pond (or draining if there is a water control structure) and allowing the sediments (and plant structures within the sediments) to freeze through the winter months. This technique is only effective on plants that reproduce through vegetative means (such as root structures or fragmentation) and may increase the production of plants that reproduce through seeds. Studies have shown that pondweeds (Potamogeton spp.) and hydrilla (Hydrilla verticillata) will increase after draw-downs.
 
 
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