Hydrilla

Exotic Aquatics of the Gulf Coast:
Water Thyme (Hydrilla verticillata)

Hydrilla: An Aquatic Nightmare

This plant is listed in the U.S. Department of Agriculture’s Federal Noxious Weed Act. This means it cannot be imported into the or transported within the United States.

Hydrilla forms dense canopies at the water’s surface that often shade out other submerged vegetation. Although it is eaten by waterfowl, it produces far more than they can comsume. The plant supports many species of fish in its early stages, but once it begins to take over, the density reduces the dissolved oxygen and the fish population — especially those species popular with anglers — move away. Water gardeners and aquarium hobbyists control this occurrence by removing plants.

Many anglers have been stopped from a day of fishing by the tangles of this plant in their favorite bayou or lake. Camp owners complain about formation of an ugly green layer on their beautiful lakes or bayous, demanding state control of the plant. At great expense, the state of Louisiana controls it as much as possible. For example, in the past couple of years, Louisiana Department of Wildlife and Fisheries (LDWF) twice drew down one of its largest and most popular fishing lakes, Lake Henderson, in an attempt to kill the hydrilla. When the lake was reflooded, the plant regenerated more densely than before in both cases. LDWF currently spends $100-200 per aquatic acre for herbicides to control this plant and attempt to maintain the state’s lakes.

Hydrilla: An Introduction
Hydrilla: An Aquatic Nightmare
Hydrilla: Unique Physical Features
Hydrilla: Online & Printed Resources

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