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Hydrilla -  Aquatic Monster Invades Indiana

 

Hydrilla

 

Hydrilla Facts

Scientific name: Hydrilla verticillata Common names: Hydrilla, Water thyme
Family: Hydrocharitaceae (Frogbit)
Class: Monocot
Sexual Expression: Both monoecious and dioceious forms. No sexual propagation in diocieous plants
Span: Perennial
Distribution: From tubers, turions, root crowns, and fragments.

*Information found at The Aquatic Plant Management Society webpage.

One of Indiana's "Most Unwanted"

Purdue University's Cooperative Agricultural Pest Survey, or CAPS, program is an online information center for invasive species in Indiana. The site provides information on how to identify, detect and manage any invasive you may come across. Click here for CAPS information on hydrilla.  

Is That Hydrilla? 

If you think you have come across hydrilla in any body of water, please report it to:
The Department of Natural Resources
Division of Fish and Wildlife
Aquatic Nuisance Species Coordinator
402 West Washington, Room W-273
Indianapolis, IN 46204

Please include a sufficient sample for testing and information including the county, waterway and the date the sample was taken.

Hydrilla

 

Beware of the aquatic monster! Hydrilla - commonly termed as the "world's worst weed" - has been found lurking in the Hoosier state. Indiana's first hydrilla sighting was confirmed at Lake Manitou in Rochester of Fulton County in August 2006. That means that other lakes and rivers in our great state are more susceptible to invasions of this aquatic nuisance if we don't take the necessary precautions.

For more information on Indiana's hydrilla infestation, check out the Department of Natural Resources' Lake Manitou Hydrilla factsheet.

What is Hydrilla?

Hydrilla verticillata is a submerged aquatic plant with heavily branched stems that grow towards the water's surface. It is characterized by its long, slender stems that can grow as tall as 30 feet and are heavily branched. The leaves are long, whorled, and bear small conical bumps on its underside. The partial evergreen will occasionally produce small white flowers as well. Usually rooted, hydrilla can also be found floating around a body of water in a large mass. Native to Asia, Africa and Australia it is considered an invasive species in the United State.

Hydrilla's presence in the United States is one of irritation as we consider it one of the "most unwanted" species in our bodies of water. The reason for our aggravation comes from the fact that hydrilla, like Godzilla terrorizing Tokyo, leaves lakes, rivers and other waterways up heaved and terrorized. The invasive specie forms a dense canopy that forces native species to compete for nutrients and blocks much needed sunlight to aquatic plants below, basically pushing out our native aquatic species out of their home.

Aquatic animals are also affected in heavily infested waters. Fish population imbalances are likely when over abundant amounts of hydrilla is present. The dense mats raise the water's pH, oxygen levels fluctuate and water temperature rises. The fish are left smaller in size and weight; sportfish populations greatly decline.

How Does Hydrilla Affect Us?

Besides adversely affecting the biodiversity and altering the aquatic ecosystem, hydrilla may greatly interfere with recreational water activities and be a strain on local economies. 

  • Intakes for drinking water, power generation and irrigation can be clogged.
  • Water quality may also degrade due to dense vegetation dying and decomposing.
  • Shoreline access, boating and swimming can be restricted by the thick growth.
  • Shallow water fishing is made impossible.
  • Depresses water-site property values.
  • The cost of managing hydrilla in water sources is high.  

    Management of hydrilla is quite expensive. Millions of dollars are spent each year in herbicides and mechanical harvesters. Unfortunately, hydrilla is practically invisible until it is too late as it is noticeable only when it tops off at the surface. The best protection is to prevent hydrilla from reaching our water sources in the first place.

    How Hydrilla Has Invaded Our Nation

    Hydrilla was introduced to the United States when dumped into a Florida canal in the 1950's. At that time, the invasive was imported and marketed as an aquarium plant. When a buyer wanted to get rid of the plant, he tossed it into a canal behind his farming business. Weeks later he noticed how fast and vast the hydrilla grew and decided to produce and sell it himself. Problems with the plant choking out aquatic species, destroying natural habitat and interfering with recreational activities began shortly after as the hydrilla grew to overabundant populations. Soon the hydrilla's invasion of U.S. waters would spread outside of Florida to other southern states and way over to California. Currently, hydrilla has been reported in 22 states including Indiana.

    Unfortunately, hydrilla has amazing reproduction capabilities that allow it to spread throughout a body of water and to other locations quite easily. It can reproduce in four different ways: through seeds, turions, tubers and fragmentation.

  • Seed reproduction is considered a minor method as the appearance of seedlings are rare.

  • Turions are compact buds that break off the parent plant into the sediment to form new plants.

  • Tubers are underground turions, forming on the roots. 

    --- Turions and tubers are the most troublesome method as a single tuber is known to produce over 5,000 new tubers per square meter. Both can remain dormant for several years before germinating, surviving ice, drying and herbicides.

  • Fragmentation is the best method for long distance dispersal. Just a sprig of hydrilla transferred to another body of water can form a new population within days.  

    What We Can Do to Prevent Further Spreading

    Introduced by dumping aquarium contents into waterways, hydrilla is now listed by the U.S. government as a Federal Noxious Weed. With this designation, it is illegal to import or sell the plant in the United States although sales made through the internet are possible. Today, the plant is mainly transported to new lakes and rivers from plant material on boats, equipment and gear worn in the water. In order to prevent the transportation of hydrilla, please consider these precautions:

  • Avoid boating through dense hydrilla mats. This will minimize fragmentation and the spreading of plants. 
  • Remove all plant fragments from the boat, propeller, and trailer before and after boating.
  • Always dispose plant fragments on the shore.
  • Rinse any mud and debris from equipment and gear before leaving a launch area.
  • Drain any water from the boat before leaving.
  • Do not dump aquarium or water garden plants outside. Seal them in a plastic bag and throw in the trash.
  • Look for Indiana native plants to add in aquariums and water gardens.                                                  --- Alternatives include Elodea canadensis or Elodea nuttallii.

    The Indiana General Assembly also has passed an "Emergency Rule" regulating Hydrilla verticillata as a pest. Click here for legal restrictions on hydrilla.

    If you think you've spotted Hydrilla verticillata in a lake, river or other waterways, immediately contact the Indiana Department of Natural Resources, Division of Fish and Wildlife. The sooner the problem is dealt with, the easier it will be to control the spreading of hydrilla.

    For More Information

    The Nature Conservancy's Information on Hydrilla

    MIPN - Midwest Invasive Plant Network

    DNR / AIS - Hydrilla

    Global Invasive Species Database from the World Conservation Union's Invasive Species Specialist Group

    Stop Aquatic Hitchhikers! - a "site for recreational users who want to help stop aquatic nuisance species"

    Union of Concerned Scientists information on hydrilla

    Illinois and Indiana Sea Grant's information on invasive aquatic plants

    Washington State's Department of Ecology

    "The Perfect Aquatic Weed" - an article discussing hydrilla's unique biological and physiological characteristics and aggressive growth habit.

    Habitattitude - " a site for aquarium hobbyists, backyard pond owners, water gardeners and others who are concerned about aquatic resource conservation"

    Minnesota Sea Grant - website containing various information on water gardening

    Educational Resources from the USDA National Invasive Species Information Center

    A Science for Kids hydrilla article

    Nature picture credits (top to bottom, left to right): Photo © Uni. of Connecticut (hydrilla mass); Photo © Vic Ramey/Uni. of Florida (hydrilla).

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