INFORMATION!

Variable-Leaf Watermilfoil(Native)
Myriophyllum heterophyllum

Common Names:  Water milfoil, Coontail, Coontail Moss

seed head of variable leaf watermilfoilDistribution and Habitat
: Milfoil is found predominately in the upper and lower coastal plain.  It thrives in older, more stabilized systems with clear, acidic water, where it may be rooted in depths up to 10 feet.  It is very common in impoundments located in the sandhills region of the midlands.  The dense growth characteristics of this plant often dominates all other aquatic growth and can seriously restrict utilization of the water body for recreation or other purposes.

variable leaf watermilfoilDescription
: Milfoil is a rooted aquatic species possessing a long, robust stem which is usually deep red or brownish red in color.  This plant may exhibit two distinctly different leaf forms.  The submerged leaves are fine, numerously dissected and are located in whorls along the stem, giving milfoil a delicate feather-like or “coontail” appearance.  This portion of the plant is usually a reddish or greenish brown in color.  The emergent leaves are found in whorls on a stalk-like portion of the stem which extends 6-8 inches above the water.  These small leaves are bright green and oval in shape.  This growth aspect of the plant is so different from the submerged portion that it is often mistaken as being another plant altogether.  This emergent growth is generally associated with mature stages of milfoil and may not be evident until late summer.  The flowers of water milfoil are located on the emergent shoots and are very small and inconspicuous, thus are not considered a good identifying characteristic for the untrained observer.

South Carolina Law requires individuals to possess a Commercial Pesticide Applicators License in Category 5, Aquatic Pest Control, before they apply aquatic herbicides if the work is done for compensation on the property of another.  A license is also required, regardless of ownership, if the application is made to an area where public access to the treated site is expected.  Private swimming lakes, where the public would exposed to the treated waters, are the most obvious example of the latter requirement.   On all public facilities, such as golf courses, driving ranges, subdivisions, condominium/apartment complexes and mobile home parks, applicators are required to possess a Category 5 License to apply aquatic pesticides.

Control Methods:

South Carolina Law requires individuals to possess a Commercial Pesticide Applicators License in Category 5, Aquatic Pest Control, before they apply aquatic herbicides if the work is done for compensation on the property of another.  A license is also required, regardless of ownership, if the application is made to an area where public access to the treated site is expected.  Private swimming lakes, where the public would exposed to the treated waters, are the most obvious example of the latter requirement.   On all public facilities, such as golf courses, driving ranges, subdivisions, condominium/apartment complexes and mobile home parks, applicators are required to possess a Category 5 License to apply aquatic pesticides.


1. Active Ingredient: Ester of 2, 4-Dichlorophenoxyacetic acid
Product Name:  Aqua-Kleen, Weedtrine II, Navigate
Approximate Cost:  $2.50/lb - $125/50lbs

Application Rates:
100-200 lbs/acre

Application Methods and Tips:
  Best results will be achieved when the herbicide is applied during the spring or early summer.  Affects of the herbicide may not be noticeable for four to six weeks after treatment.  Granular 2, 4-D should be applied in a broadcast fashion by the use of a fertilizer or seed spreader to ensure uniform coverage of the treatment area.  Generally, control will be confined only to those areas in which the herbicide is applied, thus allowing spot treatment of selected areas where weed control is desired.  Higher application rates will be required in situations of dense weed growth, water greater than five feet deep or ponds with a short retention time (high volume turnover).  Follow-up applications may be required to gain desired control. Care should be exercised when treating ponds with dense growths of vegetation to prevent oxygen depletions due to decomposing plants.  No more than one-third of the pond should be treated at once, allowing 14-21 day intervals between applications.  Additional product directions and precautionary statements are listed on the herbicide container.  READ AND FOLLOW THE HERBICIDE LABEL.

Use Considerations:
  Do not use water from treated areas for irrigating plants or mixing sprays for agricultural or ornamental plants. Unless an approved assay indicates the 2,4-D concentration is 70 ppb (0.07 ppm) or less, do not use water from treated areas for potable water (drinking water).

2.  Active Ingredients:
Diquat dibromide salt
Product Name: Reward, Weedtrine D, Aqua-Clear
Approximate Cost:  $70 - $90/gallon

Application Rates:
1-2 gal/surface acre

Application Methods and Tips:
To control infestations of water milfoil with diquat a rate of 2 gallons per acre at a depth of 4 feet is needed.  For areas with depths less than 4 feet follow the chart detailing the gallons per acre for each depth less than four feet on the herbicide label.  For heavy infestations and depths over 2 feet deep surface spraying is not recommended.  In areas of early growth or light infestations, evenly distribute herbicide by pouring over the treatment area in strips 40 feet apart.  Dilution with water may be required in order to adequately cover the treatment area.  Treatment of water milfoil with this herbicide is more effective in low flow situations.  Do not apply diquat dibromide in muddy water as the herbicide will be inactivated.  Additional product directions and precautionary statements are listed on the herbicide container.  READ AND FOLLOW THE HERBICIDE LABEL.

Use Considerations: 
Do not use treated water as a drinking water source for 3 days after in water treatment.  Do not use treated water for livestock or domestic animal consumption for 1 day after in water treatment.  Do not use treated water for irrigation to turf and landscape ornamentals for 3 days after in water treatment.  Do not use treated water for irrigation to food crops and production ornamentals for 5 days after in water treatment.  There is no fishing or swimming restrictions for this aquatic herbicide.

3. Active Ingredient: 
ammonium salt of imazamox
Product Name: Clearcast
Approximate Cost:  $185/gallon

Application Rates:
1-2 gal/surface acre

Application Methods and Tips:
Imazamox may be used to treat variable leaf milfoil once the emergent tips of the plant have appeared above the surface of the water.  The milfoil should be treated with a desired active ingredient concentration of 100 to 200 parts per billion.  Follow the chart on the herbicide label in order to calculate the correct rate.  For example, with a depth of 4 feet the correct concentration would be 1 to 2 gallons per acre.  Always, use a high quality surfactant to ensure best results.  READ AND FOLLOW THE HERBICIDE LABEL.  
Use Considerations:  There are no restrictions on livestock watering, swimming,
fishing, domestic use, or use of treated water for agricultural sprays.  Imazamox may be applied to potable water sources at concentrations up to 500 ppb to within a distance of 1/4 mile from an active potable water intake.  Within 1/4 mile of an active potable water intake, imazamox may be applied, but water concentrations resulting from injection and/or foliar applications may not exceed 50 ppb. If water concentrations greater than 50 ppb are required, then the potable water intake must be shut and, if necessary, an alternate water supply be made available until the water concentration can be shown to be less than 50 ppb by an acceptable method.  Do not use any imazamox treated water for irrigation purposes less than 24 hours after treatment.   Read the herbicide label for the other irrigation restrictions that pertain to treatments of different types of waterbodies.

4.  Sterile Grass Carp (White Amur)

Grass carp are generally not considered and effective alternative for the control of established infestations of water milfoil.  They may be utilized as a preventative measure or in situations in which the weed growth has been significantly reduced with herbicides, but should not be stocked as the initial or primary means of controlling water milfoil.

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