DETAILS ABOUT THE AQUATIC HERBICIDES
USED IN FLORIDA

This is a supplementary part of the Herbicidal Control page of this web site.

MAIN INDEX | Copper, chelated | Diquat | Endothall |
Fluridone | Glyphosate | 2,4-D | Triclopyr | Imazapyr |

Applying a time-release granular herbicide

IN 2003, THERE ARE 8 AQUATIC HERBICIDES registered for use in Florida waters. That is, there are 8 active ingredients (chemical compounds) approved for use; these active ingredients may be formulated and sold under various trade names, names such as Aquathol, Rodeo and Sonar. They are applied directly to the target plant or dispersed within the water with the intent to cause plant death. These herbicidal compounds are purchased and used by government environmental management agencies, by private management companies, and by farmers and homeowners. Florida government permission (permits) may or may not be legally required for each instance of aquatic herbicide use.

According to the plant species being treated, the location of the infestation, the time of year, the weather, the water-oxygen levels, and a host of other variables, the aquatic herbicides may be applied directly to the plant, directly to the water, or to the plant and the water at the same time. Or they may not be permissible at all.

It is up to the user to follow the label and to do exactly as described. The label is the law.

Here is information for herbicide applicators, taken from the Aquatic Herbicide Applicator Manual (Langeland, 1998), which defines herbicides, discusses their classifications, characteristics, effects on plants, and formulation types. Also see the Herbicidal Control page on this web site to find out how and under what conditions these herbicides are used in the field; learn their water-use restrictions, learn about herbicide toxicity, walk through the EPA registration testing regimen; find out about permitting and other regulations, etc.

The following is specific information about aquatic herbicides

But first, some terms:

the lethal plant dose is the amount of herbicidal active ingredient that is required to kill a plant; it is often measured in parts per million or parts per billion

a contact herbicide is one that causes injury to plant tissue where contact occurs; contact herbicides kill relatively quickly

a systemic herbicide, or translocated herbicide is one that is absorbed into the plant through the leaves, stems or roots and translocated throughout the plant to kill it from the inside; systemic herbicides kill less quickly than do contact herbicides

a broad-spectrum herbicide is one that kills a wider range of plants than does a narrow-spectrum herbicide

liquid formulations are herbicidal active ingredients that are suspended in liquid; liquid formulations may be best for certain species of plants and/or certain management situations, such as areas where water movement is slow, or areas where there are deep sediments

dry formulations are herbicidal active ingredients that are mixed into dry, slow-dissolving pellets or granules; dry formulations make it easier to "time-release" herbicide into the water or soil at the lethal plant dose rate in areas where water movement would quickly dilute liquid formulations

the herbicide's label is a legal document that tells you what kinds of sites (ex: lakes, flowing waters, canals, reservoirs...) legally may be treated with the herbicide; how to use the herbicide; what rates to use for specific plants and environmental situations; lists precautionary statements relative to the herbicide's possible hazards; and describes specific first aid

the herbicide's MSDS (Material Safety Data Sheet) presents specific, technical information that might be useful in the event of a spill or misuse, and includes hazardous ingredients, physical data, fire and explosion data, reactivity data, health hazard data, spill or leak procedures, special protection measures and special precautons

Copper has long been widely used in natural and industrial waters for algae control, often applied simply as blue copper sulfate crystals applied into the water. Today in Florida however, "chelated copper" is most often used for aquatic plant and algae management. "Chelate" is a chemistry term meaning combining a metal ion, in this case, copper, with an organic molecule, in this case, triethanolamine or ethylenediamine. Chelated liquid copper products reportedly remain in solution longer than do copper salts (when applied to hard water) - copper that is in solution (suspended in the water) for a longer time has greater effect on the aquatic plants and algae that they are meant to kill.

Because it is an element, copper will accumulate in the sediments regardless of its bioavailability. The DEP permits the use of copper herbicides in waters only when no alternative management options are available.

Several brands of copper are available for aquatic plant and algae control in Florida; however the chemistry and mode of action of each is similar. They include Cutrine, Komeen, Copper-Z, Nautique, Captain, Clearigate, and K-Tea.

For more information about copper herbicides, as contained in the DEP Florida Aquatic Plant Survey Report, and for links to manufacturers, go here.

Diquat kills aerial parts of plants in 24-36 hours. It is water soluble and diffuses rapidly through the water and quickly adsorbs (sticks) to plants. However diquat also is strongly cationic and so quickly adsorbs to and is tightly held by the negative charges of clay and peat; thus, diquat is ineffective in muddy waters. For quick hydrilla control, for example to control pioneer populations in and around boat ramps, diquat and chelated copper mixed together make a good combination: repeated treatments during each growing season are necessary to maintain hydrilla at low levels.

Reward, Weedtrine-D and Eliminator are brands of diquat labelled for use in aquatic sites in Florida.

For more information about diquat herbicide, as contained in the DEP Florida Aquatic Plant Survey Report, and for links to manufacturers, go here.

Endothall primarily functions as a contact herbicide, but it also is somewhat mobile in plant tissues. Endothall is absorbed by submersed plants in lethal concentrations in 12-36 hours depending on the concentration applied. Usually, two or more applications are required each year to maintain hydrilla control.

Only a few formulations of endothall are registered for use in aquatic sites in Florida: the endothall inorganic salts, Aquathol K and Aquathol Super K; and the endothall amine salts, Hydrothol 191 and Hydrothol Granular.

For more information about endothall herbicides, as contained in the DEP Florida Aquatic Plant Survey Report, and for links to manufacturers, go here.

Fluridone is used for the control of various submersed plants, and some floating-leaved plants, duckweed and salvinia. It does not control algae. Fluridone applicaton rates for plant control are much lower than are those for other herbicides: µg/l (parts per billion) compared to mg/l (parts per million). However, contact time required to control target weeds is measured in weeks or months rather than hours or days. Fluridone concentrations in the water must remain for 45-80 or more days for optimum long term control of hydrilla. This aquatic herbicide is available as liquid and as slow- and fast-release pellet formulations.

Fluridone is formulated into two brands that are registered for use in aquatic sites in Florida: Sonar and Avast.

For more information about fluridone herbicides, as contained in the DEP Florida Aquatic Plant Survey Report, and for links to manufacturers, go here.

Glyphosate controls plants that are above the water; it does not control plants which are completely submersed or have a majority of their leaves under water. It is used to control a variety of annual and perennial broadleaf weeds and grasses, as well as certain floating plants. Selective management of plants using glyphosate is achieved only by careful application because, in general, glyphosate controls most plants it contacts.

Rodeo, Eagre, Touchdown Pro and other brand formulations of glyphosate are registered for use in aquatic sites in Florida.

For more information about glyphosate herbicides, as contained in the DEP Florida Aquatic Plant Survey Report, go here.

The granular formulations of 2,4-D sink to the bottom and slowly release herbicide into the water; granular 2,4-D is applied for the control of water milfoil species, and for some floating-leaved species. The liquid formulations of 2,4-D are mixed with water and sprayed onto the leaves of water hyacinth and other broadleaf aquatic weeds.

Several brands and formulations of 2,4-D are registered for use in aquatic sites in Florida. They include Navigate, Weedar 64, and Weed Rhap A-4D.

For more information about 2,4-D herbicides, and links to manufacturers, go here.

Three formulations of triclopyr are registered for use in wet sites in Florida: Garlon 3A, Garlon 4, and Pathfinder II.

For more information about triclopyr herbicide, and links to manufacturers, go here.

IMAZAPYR is the newest herbicide to be allowed for control of aquatic plants in Florida. Arsenal and similar products that contain imazapyr are used for woody plant control and difficult to control grasses in terrestrial sites, non-irrigation ditch banks, and wetlands, but they can not be applied directly to water for control of aquatic plants. Habitat is the only imazapyr-containing product that can be applied directly to water for control of aquatic plants. Imazapyr is used for difficult to control herbaceous aquatic plants such as torpedograss and woody species growing in the water, such as melaleuca. It can also be used for floating-leaf species. It is sometimes mixed in low concentrations with a glyphosate-containing product. Imazapyr is not recommended for control of any submersed aquatic species. Label cautions relative to damage to non-target vegetation and irrigation precautions must be carefully followed. For a list of aquatic plants that are sensitive to imazapyr and other aquatic herbicides, visit http://edis.ifas.ufl.edu/pdffiles/AG/AG26200.pdf.

For more information about imazapyr herbicide, and links to manufacturers, go here.