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Frequently Asked Questions

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Scientific studies strongly indicate that invasive non-native plants harm Florida's natural environment and lead to a loss of biodiversity. Many of Florida's unique native plant and animal communities are found nowhere else in North America. Invasive non-native plants disrupt Florida's natural environment by forming novel habitats and by altering ecological processes that permit native plant and animals to survive. For example, the Australian melaleuca tree forms dense forests in formerly treeless saw grass marshes of the Florida Everglades. Melaleuca trees also alter ecological processes by increasing soil elevations and by changing natural fire regimes that destroy the uniqueness of the Everglades. Endangered plants, animals, and native ecosystems are being pushed closer to extinction by invasive non-native plants.

It is estimated that more than 1.7 million acres of Florida's remaining natural areas have become infested with non-native plant species. Hydrilla, Florida's most widespread invasive exotic aquatic plant, covered 45,406 acres of public waterbodies in 2007 in 199 public water bodies.  At least 45% of the invasive non-native plant species found in Florida were imported for ornamental or agricultural reasons, and 39% of the worst invasive plant species are still commercially available for sale and continue to spread.

Public land managers, who are charged with preserving and restoring Florida's remaining native ecosystems, have found themselves spending more and more time controlling and removing invasive non-native plant species. Current control methods employed range from hand pulling of undesirable species to applying herbicides selectively to avoid harming native plant and animal communities.

Plants form the base of the food pyramid upon which all living things depend on. Aquatic plants turn sunlight into plant matter and forms the base of the food pyramid that nurtures all aquatic animals.

Benefits of aquatic plants include:

  • Nursery areas and shelter for small fish.
  • A buffer zone preventing bank erosion from waves and boat wakes.
  • A food source for fish, waterfowl, and manatees.
  • A natural water purification system.
  • Aesthetically pleasing wild flowers.
  • Nesting sites for birds.

A weed is a plant growing where it's not wanted. By this definition, any aquatic plant has the potential to be a weed if it hinders navigation, water movement in irrigation and flood control canals, swimming, recreational boating or fishing, or if it's abundant growth adversely affects fish populations and other wildlife.

The vast majority of plant species growing in Florida waters are considered beneficial and only rarely become a problem. The major weed species clogging Florida's waterways are non-native plants (non-native), like water-hyacinth and hydrilla, and were introduced from foreign lands. In the absence of natural enemies, these non-native weeds grow uncontrolled and rapidly invade new areas. Most native plants have biological restraints that limit their abundance. Uncontrolled growth of non-native plants disrupt the delicate ecological balance of Florida's waterways by destroying native habitat for fish and wildlife, and by destroying the biodiversity.

Hydrilla, first introduced from Sri Lanka into Florida during the early 1950's, can infest and cover an entire water body in as little as three years. By 1991, hydrilla infested more than 40 percent of Florida's public lakes and rivers.

A native of South America, the floating water hyacinth was first introduced into Florida during the late 1800s. It grows extremely fast, capable of doubling in area in as little as two weeks. Control programs in recent years have been successful in reducing water-hyacinth to low levels in most of Florida's public waterways.

Native plants are not targeted for control unless they have become noxious. Under the maintenance control program, even small patches of floating noxious weeds are sprayed. Sometimes they are mixed in with native plants which unintentionally get sprayed while trying to control the exotics. Herbicides formulations are used that will kill the non-native species, but will only temporarily "brown" the natives.

Spray crews are directed to minimize, as much as possible, exposure of herbicides to native plants. However, weather and water conditions do sometimes change unexpectedly and lead to an adverse and unintended impact on some native plants. Also, the natural browning of plants due to seasonal change, and damage caused by insects or disease, is also sometimes confused with the effects of the herbicides on aquatic plants.

Many people become quite concerned when they see aquatic plants being sprayed with herbicides in Florida waters. Their concerns seem to focus in two areas. First, they believe that all aquatic plants in Florida waters are beneficial to the environment, not realizing that many of these aquatic plants are not native to Florida, but are invasive non-native species that are quite harmful. Second, they believe that the use of any herbicide in water must be extremely harmful to the environment. They fail to understand that not only are approved aquatic herbicides safe to use in water when properly applied, but failure to keep invasive non-native aquatic plants under control would be devastating to the environment.

The Invasive Plant Management section, within the Florida Fish and Wildlife Conservation Commission, administers a program involving state, federal, and local governments that is designed to ensure statewide management of noxious aquatic weeds and to protect our valuable natural ecosystems. This program recognizes the important role native aquatic plants play in aquatic ecosystems, and these native plants are not the target of control activities except in those rare instances when they have become noxious and create problems for navigation, flood control, or other public welfare considerations.

This program is focused on bringing invasive, non-native aquatic weeds under what is called maintenance control. Noxious aquatic plants are those that have the potential to hinder the growth of beneficial aquatic plants, to interfere with irrigation or navigation, or to adversely affect the public welfare or the natural resources of this state.

This concept is not new or unusual. Anyone who maintains a car, or a lawn, practices the maintenance control concept. Preventive maintenance on a car is when one frequently spends small amounts of time and money to prevent major breakdowns or repairs that can cost much more or perhaps even the loss of the use of the car. For example with a lawn, one would not allow the grass to become too tall or allow weeds or some other lawn pest to kill all the grass before taking some corrective action. Maintenance control prevents damage to a lawn and limits the time, effort and money necessary to keep it attractive and in good health.

Maintenance control is the preferred method of managing noxious aquatic vegetation such as hydrilla, water-hyacinth and water-lettuce. To understand what maintenance control is, it is best to first understand what it is not. First, it is not allowing our lakes or rivers to become completely covered with noxious, aquatic weeds. Letting noxious aquatic weeds take over a water body may not only render that water body virtually unusable for recreation or fishing, but it may also displace desirable native plants, adversely affect fish and wildlife populations, interfere with flood control, irrigation, and potable water uses.

Maintenance control is not allowing certain aquatic plants to build up to levels that provide habitat for disease carriers such as some species of mosquitoes, or to present other health and safety dangers to the public. To allow such things to occur before any effort was made to manage these noxious plants, would be considered crisis management.  When workers are out managing noxious, aquatic weeds, they are normally conducting maintenance control, not crisis management.

What then is maintenance control? Florida law defines maintenance control as a method of control in which techniques are utilized in a coordinated manner on a continuous basis in order to maintain the plant population at the lowest feasible level as determined by the Fish & Wildlife Conservation Commission. In every day language, that means maintenance control is a systematic, planned approach for controlling noxious aquatic weeds. The specific goals and objectives of each management plan are developed through interagency coordination and public input.

Federal, state, and local agencies spend millions of dollars each year to control aquatic weeds in Florida. The Florida Fish and Wildlife Conservation Commission has been designated by the Florida Legislature as the lead agency to control aquatic weed problems in public waters. The Invasive Plant Management section administers funding programs for this control and issues permits for private and commercial aquatic weed control. Also, there are laws restricting the importation and cultivation of foreign aquatic weed pests to prevent the establishment of new weeds. Research on the chemical, biological and mechanical control of aquatic weeds presently is conducted by scientists at Florida Fish and Wildlife Commission, United States Department of Agriculture, United States Army Corps of Engineers and many of Florida's major universities.

* Boat trailers are one of the major sources of moving exotic aquatic weeds from one water body to the next. Before you leave a boat ramp, carefully inspect your trailer and boat for aquatic weeds. Many plant species can grow back from even tiny fragments, thereby infesting new water bodies.

* Never transplant aquatic vegetation without first contacting a Florida Fish and Wildlife Conservation Commission aquatic biologist.

* Never empty the contents of your home aquarium into the wild. Many aquarium plants are imported from around the world and could become a nuisance weed in Florida's waters.

* Report new infestations of pest species such as water-hyacinth and hydrilla to the Florida Fish and Wildlife Conservation Commission's regional biologist in your area.

* Consult with one of the Florida Fish and Wildlife Conservation Commission's regional biologists before controlling any aquatic weeds since many water bodies require an Aquatic Plant Control Permit. Report aquatic herbicide misuse and fish kills to the Florida Fish and Wildlife Conservation Commission, Invasive Plant Management section (850) 617-9430.

Herbicides registered for use in aquatic environments undergo years of evaluation with the U.S. Environmental Protection Agency (EPA) including more than 140 tests related to human and environmental impacts. In their concentrated form, all herbicides should be handled with great care. However, EPA explains that when an EPA-registered herbicide is used according to the label directions, it will cause no unreasonable adverse effect on human health or the environment. Further, before an herbicide can be sold for use in Florida waters, it must be registered with the Florida Department of Agriculture and Consumer Services. During this process, state health and environmental agencies comment on new herbicides, as well as, new use patterns for previously registered herbicide compounds. The FWC continuously contracts with universities and other research institutions to find the most environmentally compatible and cost-effective strategies to apply herbicides to control target vegetation while conserving or enhancing non-target plants and animals.

No, only the amount of herbicide needed to adequately control aquatic weeds is allowed for use. The department spends less money for the control of water-hyacinth and water-lettuce each year due to the success of the Commission's maintenance control program, and far less herbicide is used to control hydrilla than was formerly used. Because large floating mats of weeds are not allowed to build-up, less chemicals are used and less muck is deposited on the bottoms of our water bodies.

Research conducted on Lake Okeechobee and other places throughout the state have consistently shown that harvesters alone are ineffective for large-scale control of these fast growing exotics. When harvesters replaced chemicals, on Lake Okeechobee the plants grew out of control. It is also far more cost effective to use herbicides than mechanical harvesters. One crew applying herbicide can cover approximately 10 acres a day, whereas a crew operating a harvester can clear only one-half acre a day.

No, all dying and decaying plants contribute to the muck layer, but the bulk of the muck comes from the natural die-off of living native plants and invasive exotic plants. Water level stabilization for flood control purposes, and prolong drought, create conditions that result in too many plants in the shallow areas. This not only reduces fish spawning areas, but results in large muck deposits.  The muck removal projects designed by the Florida Fish and Wildlife Commission with maintenance control, help offset this problem.

Florida Fish and Wildlife Commission biologists and university researchers have conducted studies on Florida water bodies that indicate that spraying does not affect the catch-ability of fish, or adversely affect bedding fish. Isolated fish kills do sometimes naturally occur due to low levels of dissolved oxygen in the water. When dead plants begin to decay and the organisms that break down the plant material use the dissolved oxygen in the water, it may adversely affect the dissolved oxygen level. That is why the department requires that the amount of dissolved oxygen in the water be tested in the area to be sprayed before control activities are undertaken to avoid fish kills. These management activities are also sometimes spread out over a five or six week period to assure no adverse affects upon the dissolved oxygen levels.

The Florida Fish and Wildlife Conservation Commission has regional biologists located around the state who can provide permitting information and make recommendations on aquatic plant control.  Please contact the office nearest you. If you would like more specific information, please contact the Invasive Plant Management section, Florida Fish and Wildlife Conservation Commission, 3900 Commonwealth Blvd., MS 705, Tallahassee, FL 32399, (850) 617-9430.

None. Although state law requires that anyone conducting a business activity using aquatic plants must be permitted by the Florida Department of Agricultural and Consumer Services (FDACS). FDACS regulate nursery and nursery stock dealers, retail outlets (pet stores) and the wild collection of aquatic plants.  For a list of FDACS office locations and inspectors please call 352/372-3505.

The short answer is "no." The Invasive Plant Management Section in FWC is responsible for the control of invasive exotic plants, both aquatic and upland, in Florida. We are limited by law to conducting and funding control projects on public conservation lands, such as state parks or national wildlife refuges. The work is performed by private companies under contract with our office. To determine if there are local grants from county or city governments to help you remove invasive plant species from your property, please contact your County Agricultural Extension Agent. In addition, they should be able to provide you with advice about having invasive plants removed and any local ordinances involved.

If you need permitting information regarding control of aquatic weeds using grass carp, contact the Florida Fish and Wildlife Conservation Commission for details, (352) 357-2951.


Herbicides registered for use in aquatic environments undergo years of rigorous evaluation with the U.S. Environmental Protection Agency (EPA).  In addition, before an herbicide may be used in Florida waters, it must be registered with the Florida Department of Agriculture and Consumer Services. During this process, state health and environmental agencies comment on new herbicides. For more information on how the process for registering pesticides and herbicides visit Florida Department of Agriculture and Consumer Services website

For more information about health and environmental assessments and other herbicide or pesticide related questions please visit the National Pesticide Information Center and the Florida Department of Agriculture and Consumer Services