Demonstration Project on Hydrilla and Hygrophila in the Upper Kissimmee Chain of Lakes

Project Need

As previously discussed, the aquatic ecosystem of central Florida has been greatly impacted by activities in the making for over one hundred years. Within the past twenty to thirty years, the exotic invasive problem has become significant and in the past two decades grown exponentially most likely due to the lack of severe freezes and the lack of normal fluctuation in the lake system. Water level stabilization, introduction of non-native species, and increases in nutrient loading, runoff and discharge have all contributed to the decline in the health and quality of the lakes in Osceola County. These activities are further degrading the natural system as well as decreasing the level of service flood control provides, which was the primary reason for altering the system to what it is today. Biological diversity decreases as invasive exotics spread out of control, forming dense monocultures in which none of the native species can thrive. This not only includes plants but also affects prime aquatic habitat, which supports numerous species of fish, waterfowl, wading birds, and wildlife (Dooris, 1976).

The primary purpose of this proposed project is to discover new herbicides, develop new technology processes or practices, or a new combination or uses of technologies, processes or practices for the purpose of proving technologically feasible and cost effective means to manage hydrilla, hygrophila and other exotic aquatic vegetation in the Upper Chain of Lakes within the Kissimmee River Basin of Osceola County. These bodies of water comprise nearly 100,000 surface acres (See Appendix C).

Exotic aquatic vegetation is a significant problem in Osceola County as well as many other counties in the State of Florida. This grant shall be used to conduct and promote the coordination and acceleration of studies that address the causes, effects, extent, prevention, reduction, and elimination of water pollution (more specifically hydrilla and hygrophila). This study will provide information on using emerging methods of aquatic weed control to promote increases in oxygen levels and restore the natural lake vegetation.


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Project Goal and Objectives

Goal: To find new and alternative methods of control for hydrilla and hygrophila in the Upper Kissimmee Chain of Lakes in Osceola County and to share these findings with the industry and public.

Objectives: 1) To evaluate the effectiveness of Experiment Use Permit (EUP) herbicides and biological controls in the treatment of hydrilla and hygrophila;

  • To evaluate new technology processes or practices, or a new combination or uses of technologies, processes or practices for the control of hydrilla and hygrophila using small-scale field work;
  • To implement and monitor successful practices and processes identified in objectives 1 and 2 using large-scale field demonstrations; and
  • To demonstrate the project efforts in alternative technologies to manage hydrilla and hygrophila and disseminate to the public the results of this project.


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Project Description and Activities

This demonstration project is a combination of studies that will result in improved water quality and natural habitat in Osceola County lakes. Hydrilla and hygrophila are exotic invasive weeds that are dominating the aquatic ecosystems by shading out natural vegetation, reducing oxygen level, increasing the amount of sediments and impacting flood control in lakes and canals. The project objectives are to evaluate the effectiveness of Experimental Use Permit (EUP) herbicides, biological controls and application methods of herbicides in the treatment and control of hydrilla and hygrophila using small-scale fieldwork and large-scale field demonstrations. Dissemination of the study findings to the public will be a large component of the demonstration factor of this project.

The primary targeted species are Hydrilla (Hydrilla verticulata) and Hygrophila (Hygrophila polysperma). Hydrilla was “first discovered in the United States in 1960. A highly specialized growth habit, physiological characteristics, and reproduction make this plant well adapted to life in submersed freshwater environments. Consequently, hydrilla has spread rapidly through portions of the United States and become a serious weed. Where the plant occurs, it causes substantial economic hardships, interferes with various water uses, displaces native aquatic plant communities, and adversely impacts freshwater habitats. Management techniques have been developed, but sufficient funding is not available to stop the spread of the plant or implement optimum management programs. Educational efforts to increase public and political awareness of problems associated with this weed and the need for adequate funding to manage it are necessary” (Langeland 1996).

“Hygrophila was imported into Florida during the early 1950's, and several waterways were deliberately stocked by aquarium plant collectors. Hygrophila is still a popular and widely distributed aquarium plant, but, because of its potential as a weed, the Department of Natural Resources prohibited its sale in Florida. Hygrophila has terrestrial and aquatic growth forms that survive in shallow acidic waters to wet soils. Unlike hydrilla, establishment of this species in deeper-than-2-m water is very slow. Hygrophila seems to grow more robustly in enriched waters (Schmitz and Nall 1984) and in flowing waters (Van Dijk et al. 1986). Control of hygrophila is difficult. Harvesters fragment plants and increase distribution, and grass carp have a low preference for hygrophila. Registered herbicides including diquat, endothall, and fluridone, provide marginal control” (McCann et al.1996).

Incidental targeted species may include: Water lettuce (Pistia stratioites), Water Hyacinth (Eicchornia crassipies), Torpedo grass (Panicum repens), Para grass (Urochloamutica), Alligator weed (Alternanthera philoeriodes), Wild taro (Colocassia esculenta), and Parrots feather (Myrophylum aquatica).

All of the above listed plant species are listed as Category I exotics by the Florida Exotic Pest Plant Council (FEPPC) as of April17, 2006 except alligator weed (Category II) and parrots feather. All of the above listed plants are recognized as invasive exotics by the Florida Department of Environmental Protection.

All necessary precautions will be made to protect non-target species, threatened and endangered plant species and wildlife in the treatment areas. Proper Personal Protection Equipment (PPE) will be required of the applicators. The herbicide will only be applied according to the label and all local, state, and federal laws. Public notices will be clear, informative, and educational in content when applicable.


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