Hydrilla: A Growing Problem for Florida Waterways

About Hydrilla

hydrillaHydrilla , the invasive freshwater plant, is spreading throughout Florida and at least twenty other states. It causes damaging infestations that choke out native plants, clog flood control structure, and impede waterway navigation and recreational usage. Every year, the State of Florida spends millions of dollars managing this weed in our waterways. However, this plant is showing resistance to the widely used herbicides fluridone and endothall. UF/IFAS Extension and Entomology and Nematology Department did a program to address the hydrilla management. This blog is an excerpt of The Hydrilla Integrated Pest Management Risk Avoidance and Mitigation Project.

How to Prevent New Hydrilla Infestations

  • Do not empty your aquarium contents into waterways.
  • Clean you boat, trailer, live wells, fishing equipment, and diving gear before and after you visit a water body.
  • Do not place any plant materials back into the water Dispose of plant materials in on-site trash cans or your own household trash.
  • Do not compost hydrilla or any other aquatic weeds.
  • Wash and brush the dogs thoroughly before they jumping into new waters.

How to Control Hydrilla Infestations

  • Physical Control
    • Hand pulling to remove the entire plant, including roots and tubers
    • Covering the sedimen with opaque fabric to exclude sunlight can control small patches of hydrilla
  • Mechanical Control
    • Mechanical harvesting is performed by specialized machines that remove hydrilla from the water, chop the plant material, and transport it to designated site on shore for disposal and decomposition. It is usually considered when the entire water body is covered by hydrilla. However, fragments left behind in the water will produce new plants.
  • Chemical Control
    • Cooper, diquat, fluridone, endothall, and imazamox are examples of aquatic herbicides that provide temporary control of hydrilla. Before using herbicides, always read and understand the labels and adhere to the recommendations.
  • Biological Control
    • Herbivorous Fish: The Asian grass carp is an effective consumer of hydrilla and other aquatic plants. However, this fish in a non-native species, a permit is required from Florida Fish and Wildlife Conservation Commission is needed before release the fish.
    • Herbivorous Insects: The Asian hydrilla leaf-mining fly has a well established field population in all hydrilla infested water bodies.
    • Pathogenic Fungus: The fungus Mycoleptodiscus terrestris (Mt) is an indigenous pathogen of hydrilla. It operates like a chemical herbicide in that it contacts, penetrates, and kills hydrilla.