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News Release
Media Contact:
TPWD News,, 512-389-8030

Sept. 19, 2005

Agencies Preparing To Fight Hydrilla In Lake Conroe

AUSTIN, Texas — In an effort to avoid repeating a scenario that occurred here more than 25 years ago, the San Jacinto River Authority and Texas Parks and Wildlife Department are making plans to control hydrilla and protect native vegetation in Lake Conroe.

Hydrilla in the lake has been increasing despite repeated efforts by the two agencies to control its spread with herbicides. “Hydrilla became a serious problem on the lake in the late 1970s, causing significant problems for boaters, skiers and swimmers,” says Dave Terre, TPWD’s Regional Director of Inland Fisheries in Tyler. “At that time it was controlled with grass carp, but the number of fish used was too large, resulting in damage to desirable native plants.”

TPWD restored native vegetation in the lake, but the resurgence of hydrilla now threatens its existence. “We cannot let hydrilla get back to the levels it once was,” says Terre. “If left unchecked, hydrilla can have negative impacts on recreational users as well as create areas of low dissolved oxygen that will be harmful to fish. It will also out-compete more desirable native aquatic plants that provide good habitat for fish”

TPWD and SJRA are developing an Integrated Pest Management plan that will emphasize the use of a variety of strategies to control hydrilla in its early stages. Possible control methods include the minimal use of herbicides, limited numbers of grass carp and perhaps other biological or mechanical methods. “TPWD has successfully used pest management in the past and will carefully monitor the lake, no matter what methods are used,” Terre says.

Hydrilla, a plant from Asia thought to have been introduced to the United States by the aquarium industry, is considered to be one of the world’s worst aquatic weeds. Unlike most native aquatic plants, hydrilla forms dense mats of vegetation at the water’s surface in 15-20 feet of water. Hydrilla covered about 40 percent of Lake Conroe in 1981, some 8,400 acres. A recent survey found the plant infests about 868 acres; a substantial increase from 2002 when it occupied only three acres.

For more information about the hydrilla control effort, contact: Earl Chilton, (512) 389-4652 or or, (979) 822-5067.

SL 2005-09-19

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