The District's aquatic plant management program targets the troublesome, invasive species hydrilla (Hydrilla verticillata), water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes).
Invasive Aquatic Plants
Many foreign plants have been introduced and currently thrive in Florida. They are cultivated, for beneficial purposes. However, some non-native plants reproduce and spread so rapidly that they damage or replace important native plant communities and degrade wildlife habitat. Non-native plants, which cause significant and negative ecological or economic impacts, or affect human health, are considered to be invasive species.
Water hyacinth is a free-floating plant native to South America. It was introduced in Florida during the late 1880s. It currently infests more than 200 public water bodies in Florida and many more private waters. Water hyacinth has a fast growth rate (populations can double in as little as two weeks) and expands rapidly on Florida waters. Unmanaged waters typically become filled with dense, floating mats of water hyacinth. This species caused such severe problems that federal efforts to control water hyacinth were initiated by Congressional action during the 1890s.
Hydrilla is a rooted, submerged plant native to Southeast Asia. It was introduced to Florida during the late 1950s as an aquarium plant and now infests approximately 175 public water bodies. It is a rapidly growing plant that has the ability to fill lakes and rivers from the bottom to the surface with a tangled mass of stringy stems. Special physiological adaptations allow hydrilla to grow in much deeper and darker water than other aquatic plant species. Because of this special ability, the growth of hydrilla is not limited to shallow shoreline areas of lakes. Hydrilla has the demonstrated potential to fill many Florida lakes and rivers from shore to shore if not controlled.
Water lettuce is a free-floating plant. Its native range and date of introduction to Florida are not known. Experts disagree on whether to consider water lettuce a native or introduced species. It has been present in Florida for a long time and occurs on hundreds of public waterways. Water lettuce reproduces and spreads rapidly, often covering significant portions of lakes and rivers.
The natural pests, diseases and other environmental conditions that limit the growth of invasive plants in their native lands are not present here. Excessive populations of invasive aquatic plants impact navigation, recreation and flood control, and decrease property values. Dense infestations can reduce dissolved oxygen levels, increasing the potential for fish kills to occur, damage fish and wildlife habitat, and significantly hinder fish management and restoration efforts. The annual growth cycle of these species, coupled with their ability to rapidly produce large, dense populations, increases the formation of sediments (muck accumulation).
Because of the well documented negative impacts of invasive aquatic plants on Florida's aquatic resources and commerce, the Florida Aquatic Plant Management Act (Florida Statute 369.22) was passed requiring that these invasive plants be managed at maintenance levels. The District conducts aquatic plant management operations on more than twenty public water bodies in cooperation with the Florida Fish and Wildlife Conservation Commission.
Populations of invasive aquatic plants are continuously monitored and controlled to maintain them at acceptable levels. Managing these troublesome plants before they get out of hand minimizes the amount of plants, which must be treated, resulting in reduced treatment costs, herbicide use, associated ecological impacts, damage to fish and wildlife habitat, and recreational impacts.
Water Use Restrictions
The use of treated waters for irrigation or other purposes may be restricted following the application of aquatic herbicides, which are used to control invasive species populations. Each product has a unique mode of action, chemical properties and research data package. For this reason, the required water use restrictions are different for each product and some aquatic herbicides have no water use restrictions at all.
Water use restrictions apply only to “treated waters.” Treated waters consist of the actual area on which the aquatic herbicide was applied, as well as an appropriate buffer or setback distance. Water use restrictions may occasionally apply to an entire lake or section of a river if a lake-wide infestation of the troublesome species hydrilla is treated.
When and where applicable water use restrictions apply the District issues a press release or posts notification signs displaying treatment dates and applicable water use restrictions.
Please check out these interesting links for more plant pictures and information relating to invasive and native aquatic plants, statewide aquatic plant management efforts, weed alerts and information on available control methods.
- Aquatic Plant Management — Florida Fish and Wildlife Conservation Commission, Invasive Plant Management Section
- Plant Management in Florida Waters — University of Florida IFAS Extension