Synopsis of Introductory Presentations

“Hydrilla Management Before Fluridone”, by Dr. Bill Haller, UF/IFAS Center for Aquatic and Invasive Plants

  • Hydrilla introduced into Florida in 1958-1960
  • Control measures included mechanical, biological, chemical measures
  • Problems with all of these strategies
  • Grass carp symposia in 1976 and 1994
  • Fluridone approved for use in 1980
  • Cost of hydrilla control with Fluridone much lower than other herbicides
  • Mike Netherland noted hydrilla resistance to Fluridone in 1999 Where to go from here
  • Current herbicides that gain USEPA approval have a single, simple, mode of action
  • Such herbicides are prone to resistance development,
  • Similar to agricultural herbicide uses, we need several different compounds to
  • However, the aquatic herbicide market is very small compared to agricultural Markets, lowering the incentive to develop new compounds
  • Use of grass carp, as a management tool is likely to increase
  • State and federal agencies may need to incur the cost of developing and testing New aquatic herbicides (third party registrations)
  • We need research and development of compounds with more than one mode of action

 

“Recent Challenges and Current Viable Options for Hydrilla Management in Florida”, by Dr. Mike Netherland, US Army Engineer Research and Development Center /Center for Aquatic and Invasive Plants

  • Management of hydrilla should include an evaluation of the relative benefits and harm in doing so
  • Hydrilla has some benefits as habitat to fish and wildlife when it is present at low densities, but high densities can have detrimental properties
  • 1990s is when hydrilla spread throughout the Kissimmee Chain of Lakes and Lake Istokpoga, where most control budget is currently spent
  • We may need to realize that current management strategies such as whole-lake
    reductions may not be compatible with current realities of viable options
  • Control of the spread of hydrilla across lakes has been unsuccessful
  • Compared to other regions, shallow lakes and warm temperatures in Florida cause hydrilla to potentially occupy a large portion of lake surface area, which is the problem.
  • Prior to resistance, Fluridone was a low-cost option to reduce large acres of hydrilla in large lakes, with little impact on native plants
  • Resistance to Fluridone was inevitable, and it developed simultaneously in several locations in Florida
  • With resistant hydrilla, it has been difficult to maintain contact times at high concentrations of Fluridone due to water management schedules, flushing rates, and bacterial breakdown of Fluridone
  • The primary issue with resistance is selectivity, because non-target impacts of
    herbicide use are certain to increase with Fluridone resistant hydrilla
  • The Kissimmee Chain and Lake Istokpoga present the major challenges due to
    resistant hydrilla and importance of native plants to those ecosystems,
    causing high risk of non-target impacts
  • We need to know if high coverage of hydrilla is a flood control threat in these lakes

 

“Current Florida DEP Management Strategies for Hydrilla in Florida”, by Jeff Schardt, FL Department of Environmental Protection

  • Management of hydrilla has reduced the total acres from 140,000 to 110,000, and the total number of water bodies from 280 to 186
  • Large-scale hydrilla control has been ineffective with mechanical removal or use of insects
  • Fluridone and Endothall are the two chemicals currently available for use on large systems
  • Grass carp remove hydrilla but are nonselective for other native plants
  • Fluridone most effective in January-May due to low rainfall increasing contact time, and lower light availability for growth
  • Fluridone tolerant hydrilla and microbial breakdown of the compound have made long contact times necessary for control difficult to obtain
  • 65% of hydrilla control total budget is spent on Lake Istokpoga and the Kissimmee Chain of Lakes
  • Lake stage and flow greatly influence the cost of Fluridone treatments, with high lake Kissimmee stage (e.g., 55 ft MSL) costing over four times the amount that a low stage (e.g., 49 ft MSL) would cost
  • Hydrilla control will require cooperation among all state and federal agencies involved in large lakes in Florida

 

“Water Management Schedules and Hydrilla Management”, by Susan Sylvester, U. S. Army Corps of Engineers, Jacksonville District

  • USACOE managed lakes in Florida are operated using regulation schedules for flood control, navigation, and water supply for agriculture and downstream flow
  • The regulation schedules have reduced variation in water levels compared to historic hydrologic regimes
  • Temporary deviations from the schedules have been used to aid hydrilla
    treatments, but they require planning and multi-agency input -Impacts of hydrilla on flood control in large lakes has not been evaluated

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