Demonstration Project on Hydrilla and Hygrophila in the Upper Kissimmee Chain of Lakes
(Excerpt from the EPA Work Plan)

Aquatics, Winter 2007 / Vol. 29, No. 4
by Tina Bond

Osceola County, Florida was awarded a $2.881 million dollar grant by the Environmental Protection Agency (EPA) to find new and alternative ways to manage hydrilla and hygrophila in the Upper Kissimmee Chain of Lakes.  The objectives of the project are:

  1. To evaluate the effectiveness of Experimental Use Permit (EUP) herbicides and biological controls in the treatment of hydrilla and hygrophila;
  2. 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;
  3. To implement and monitor successful practices and processes identified in objectives 1 and 2 using large-scale field demonstrations; and
  4. To demonstrate the project efforts in alternative technologies to manage hydrilla and hygrophila and disseminate to the public the results of this project. 

The primary targeted species are Hydrilla (Hydrilla verticillata) and Hygrophila (Hygrophila polysperma).  “Where hydrilla 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 is still a popular and widely distributed aquarium plant, but, because of its potential as a weed, the Department of Environmental Protection prohibited its sale in Florida.  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 stratiotes), Water Hyacinth (Eichhornia crassipies), Torpedo grass (Panicum repens), Para grass (Urochloa mutica), Alligator weed (Alternanthera philoxeriodes), Wild taro (Colocasia esculenta), and Parrots feather (Myriophyllum aquaticum). 
 
This project will not only benefit the waterways in Osceola County, but may have potential applications for other high-flow sites in the State of Florida such as Lake Rousseau, Lake Seminole, and Lake Istokpoga.

Since the early 1900’s, there have been numerous drainage projects to alleviate flooding or to drain the land for agricultural use.  The Central and South Florida (C&SF) Flood Control Project of the 1960’s completely changed the natural system in Osceola County as well as other parts of the state.  Projects like the C&SF Project have altered the natural hydrologic processes to such an extent that historical high and low stages are no longer recognizable.  High water levels in the summer months during the rainy season and low water levels in the winter months during the dry season were the normal hydrologic processes that occurred.  In the past, water levels fluctuated naturally between five and ten feet.  Currently, structures like weirs, locks and levees maintain water levels high in the winter and low in the summer, with little fluctuation in water levels, the exact opposite of the normal processes.  Introduction of non-native species, increases in runoff, nutrient loading, and discharge, and ideal conditions for plant growth in Florida have encouraged the growth of exotics plants.

Aquatic invasive plants have been able to thrive in Florida because of the lack of normal fluctuation within the lake system coupled with the lack of severe freezes that could help reduce the impacts of these exotic plants.  Water quality and overall health of the lakes in Osceola County have been in decline because of increases in nutrient loading, invasive plant introductions, and the stabilization of water levels.  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 demonstration project is needed because the aquatic ecosystems in Osceola County have been deeply impacted by drainage projects that have occurred over the years.  As a result of drainage projects, there has been a tremendous increase in the amount of aquatic invasive plants throughout the County and State.

There are four elements of the project headed by leading researchers in Aquatic Plant Management that will accomplish the goals and objectives of the project:

  • Element 1: Development and Testing of New Aquatic Herbicides, coordinated by Dr. William Haller of the University of Florida, Agronomy Department.
  • Element 2: Evaluation of Currently Registered Herbicides for Control of Hydrilla and Hygrophila, coordinated by Dr. Michael Netherland with the U.S. Army Corps of Engineers.

Element 3: Biological Control on Hydrilla and Hygrophila

  • Element 3, Task 1: Demonstration of Hydrilla Control in Osceola County, Florida using Mycoleptodiscus terrestris (Mt), a New Contact Bioherbicide, for Aquatic Plant Management (Project Ongoing), coordinated by Dr. Mark Heilman with SePRO Corporation.
  • Element 3, Task 2: Foreign Exploration for Natural Enemies of Hygrophila, coordinated by Dr. James Cuda of the University of Florida, Entomology/Nematology Department.
  • Element 3, Task 3: Collaborative Effort to Search for Natural Enemies of Hydrilla in East Africa (Project Ongoing), coordinated by Dr. William Overholt of the University of Florida, Biological Control Research and Containment Laboratory.
  • Element 4: Demonstration and Outreach, coordinated by Dr. Tina Bond with UF/IFAS Osceola County Extension Services.

Element 1, Development and testing of new aquatic herbicides, is coordinated by Dr. William Haller, well known aquatic plant researcher at the University of Florida and Director of the Center for Aquatic and Invasive Plants.  Dr. Haller will be evaluating EUP (Experimental Use Permit) herbicides for effectiveness on hydrilla and hygrophila.

Agrichemical companies have a renewed interest in developing herbicides for use in aquatic environments.  Many of the new products coming to market are reduced-risk pesticides, meaning that these products have low risk or impacts to human health and non-target organisms such as fish, birds, and plants.  Reduced risk pesticides also have very low potential for groundwater contamination, lower use rates and low resistance potential, something of utmost importance to aquatic plant managers.
 
There are two main tasks for Element 1: determining field selectivity, efficacy and water residues of new aquatic herbicides and laboratory/greenhouse screening and preliminary evaluation of potential new aquatic herbicides.  Researchers will learn how to determine water residues and impacts of new herbicides on target and non-target species in ponds and lakes.  Researchers will also investigate the time: rate relationships, selectivity and phyto-toxicity of potential new aquatic herbicides to determine feasibility of further registration.

As coordinator of Element 2, Dr. Netherland will evaluate currently registered herbicides for control of hydrilla and hygrophila.  Of the nine active ingredients currently registered for aquatic use, only four of these compounds (fluridone, endothall, diquat, copper) have been proven effective for hydrilla (Hydrilla verticillata) control.  The products that form the backbone of most state-funded hydrilla control programs include fluridone and endothall.

Due to the limited number of registered products, work on hydrilla control will be focused in the following areas:

  1. Evaluations of endothall in high flow areas of the Kissimmee Chain of Lakes or in other Osceola County Lakes where drip applications can be evaluated.
  2. Evaluations of endothall use in the fall and winter for control of hydrilla.
  3. Evaluations of endothall in shallow-water environments, with an emphasis on initial efficacy and longevity of control.

The proposed projects will generally include initial laboratory (replicated trials inside) or mesocosm (replicated trials outside) validation work, followed by field-scale demonstrations using the most promising techniques. While fluridone does represent an existing and important technology, knowledge on use patterns for both fluridone-resistant and fluridone-sensitive strains of hydrilla is extensive within Osceola County. There is a greater need to focus attention on developing information on the other existing molecules to help us reduce reliance on fluridone.

Element 3, Biological Control on Hydrilla and Hygrophila
Classical insect biological control can be particularly successful at controlling invasive pests of foreign origin.  The underlying principal of classical biological control is that pests are kept in equilibrium in their native ranges by a complex of biological checks and balances such as insects, diseases, nematodes and other biological organisms.  When introduced into another geographical location, away from these natural checks, the organism proliferates and becomes a serious pest.  Thus, classical biocontrol of weeds consists of determining the native range of an exotic plant and searching that range for natural checks and balances with the goal of determining safety of the controlling organism and introducing it into the area where the weed is a pest.
               
Element 3, Task 1, Mycoleptodiscus terrestris, or Mt, bioherbicide studies are being conducted by Dr. Mark Heilman.  Dr. Heilman’s research will focus on evaluating the effectiveness of Mt in the treatment of hydrilla.  

First discovered in the early 1970’s, Mycoleptodiscus terrestris still remains to be fully developed as an operational tool for aquatic plant management.  Early developmental efforts failed to reach the level of product stability and virulence needed to allow the aquatic plant pathogen to be fully commercialized.  This ongoing collaborative effort between the USDA-ARS-NCAUR, the Aquatic Plant Control Research Program at the Environmental Laboratory of the US Army Engineer Research and Development Center, and SePRO Corporation has developed new fermentation methods that enhance Mt virulence on hydrilla while providing a new dry, stable Mt material that can be incorporated with other materials and stored for several months or more prior to use.  Latest research efforts have focused upon development of new dry Mt formulations using the new production methods with the goals of enhancing attachment of Mt propagules to treated hydrilla and further improving overall performance to reach commercially viable levels of activity and efficacy.  History of biocontrol using plant pathogens has shown that formulation adjustments can have profound impact on the effectiveness of such pathogens for plant pest control.  Early work has documented a several fold increase in Mt activity on hydrilla by addition of relatively simple formulating agents to the new dry formulation. 

There have been no studies of significance that have been conducted to seek biocontrol agents for hygrophila to date.  Element 3, Task 2, coordinated by Dr. James Cuda, will initiate foreign exploration of natural enemies of hygrophila in India.  Dr. Cuda will establish collaboration with scientists and institutes in the native range of hygrophila, seek natural enemies of hygrophila, and culture and evaluate these for potential introduction into quarantine in Florida. 

Institutions and scientists in the native home of hygrophila will be sought as cooperators in this study.  Populations of hygrophila in India will be located by consultation with taxonomists and reviewing herbaria records.  Natural populations of hygrophila will be sampled for insect herbivores by standard insect collection techniques, sweep nets, black lights and maintaining in culture to allow any insect eggs and larvae to develop.  Insects will be identified to the furthest extent possible and cultured on hygrophila to increase populations and then placed back on insect free hygrophila to determine the extent of herbivory.  Following preliminary testing for host specificity in India, insects will be considered for seeking USDA approval for introducing into quarantine in the US.

Element 3, Task 3, Collaborative Effort to Search for Natural Enemies of Hydrilla in East Africa is coordinated by Dr. Bill Overholt.  The search for natural enemies (insects primarily) of the invasive submersed weed hydrilla has been concentrated in Southeast Asia and Australia over the past 30 years.  Several potential insect biocontrol agents have been introduced, but these have not had significant impact on hydrilla growth.
               
Hydrilla has been present, according to herbaria records, in East Africa for 150 years, but it has never become a problem and occurs in low densities with other native submersed species.  There is a distinct possibility that hydrilla is native to East Africa.  If in fact it is, the geographical area may have herbivores that are specific to hydrilla and it has never been adequately surveyed for potential insect biocontrol agents.

Some of the activities for this component include:

  • A collaborative agreement with International Center of Insect Physiology and Ecology (ICIPE) in Kenya will be established early in the project.
  • Literature, herbaria and new field survey data will be used to develop a geo-referenced database of hydrilla occurrence in East Africa. 
  • Hydrilla specimens will be analyzed for molecular structure and compared to Florida hydrilla molecular structure in order ascertain whether the hydrilla is similar enough in structure for biocontrol viability. 
  • Insects will be collected and evaluated for herbivory on hydrilla.
  • Arthropods, which appear to be specific to hydrilla and cause measurable damage to plants, will be imported into quarantine in Florida for host range studies following approval of federal and state authorities. 

Element 4, Demonstration and Outreach, is coordinated by Dr. Tina Bond.  The main goal is to demonstrate the results of this project to the local applicators, non-scientific public, as well as to federal, state and local government partners. Dr. Bond will develop a series of demonstration and outreach strategies in cooperation with the UF Center for Invasive and Aquatic Plants (CAIP) Information Office.  The demonstration and outreach portion of this project features a variety of methods to demonstrate progress on the project and implementation of new alternative management strategies. 

Although we have been struggling with invasive plant problems for more than a century in this state, most people are unaware of the severity of the situation.  The most effective, long-term method for preventing the spread of aquatic invasive plants is an informed citizenry.  A concerted public information campaign in Osceola County will go a long way in getting the word out to lake residents and other user groups who can help us stem the flow of invasive species by being aware of the problem and on the lookout for existing infestations or potential ones.  This will ultimately benefit all Floridians, whose tax dollars are being spent each year to mitigate the damage being inflicted by a number of highly invasive species.  The information developed in this project can then be used as a template for similar public outreach efforts throughout the state.

The most important benefit realized as a result of performing the following demonstration project will be the dissemination of information to the general public from the various experiments and trials we perform.  It is our goal to incorporate graduate students, student interns and professors into many elements of the proposed project, such that one result will be research papers created for conference presentations and/or publishing, graduate student theses, as well as reports prepared for publishing in scientific journals.  The Hydrilla and Hygrophila Demonstration Project interactive website provides specific project details and research results. It will be updated as the project progresses and will be available to all Internet users worldwide.

For more information and the complete Work Plan, please visit the website at: http://plants.ifas.ufl.edu/osceola

References

Dooris, P.M., and Courser W.D.  (1976). Determining the stages of fluctuation schedule for regulated lakes in central and south Florida.  Florida Scientist 39(1):14-18.

Feller, E., Bodle M., Harris, E. (1998). The progression of hydrilla management in the Kissimmee Chain of Lakes.  Aquatics, 20 (1).

Getsinger, Kurt et al. (2005). Aquatic Plant Management: Best Management Practices in Support of Wildlife Habitat.  The Aquatic Ecosystem Restoration Foundation.

Langeland, K.A. (1996). Hydrilla verticillata(L.F.) Royle (Hydrocharitaceae), "The Perfect Aquatic Weed". Castanea 61:293-304.

Lawrence, Kimberly et al. (2007). Demonstration Project on Hydrilla and Hygrophila in the Upper Kissimmee Chain of Lakes, Revised Work Plan for EPA Grant #X796433105-1. Engineering Department and Extension Services, Osceola County Board of County Commissioners. http://plants.ifas.ufl.edu/osceola

McCann, J.A. et al. (1996). Nonindigenous Aquatic and Selected Terrestrial Species of Florida.  University of Florida, Center for Aquatic Plants: Gainesville, Florida.http://plants.ifas.ufl.edu/mcplnt1l.html  

Myers, R.L. and Ewel, J.J. (1990). Ecosystems of Florida.  University Press/Gainesville: Florida.

Netherland, M.D., K.D. Getsinger and E.G. Turner. (1993). Fluridone Concentration and Exposure Time Requirement for Control of Hydrilla and Eurasian Water milfoil. J. Aquatic Plant Management 31:189-194.

Schmitz, D.C. and L.E. Nall. 1984. Status of Hygrophila polysperma in Florida. Aquatics 6(3):11-13.

Van Dijk, G.M., D.D. Thayer, and W.T. Haller. 1986. Growth of Hygrophila and Hydrilla in flowing water. J. Aquat. Plant Manage. 24: 85-87.