Hydrilla rediscovered on Lake Conroe

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The Texas Parks and Wildlife Department (TPWD) recently confirmed the return of Hydrilla on Lake Conroe for the first time since 2010. This summer, less than a tenth of an acre of hydrilla were found in the Caney Creek arm of Lake Conroe, which spans over 20,000 acres. The small hydrilla colony was immediately treated with a targeted herbicide application.

TPWD and the San Jacinto River Authority plan to strictly control current and potential future hydrilla growth, while promoting the establishment of native vegetation for fish and wildlife habitat at the lake. The plan achieves this by implementing a combined approach, focusing on targeted herbicide applications and the stocking of a conservative number of triploid grass carp. Targeted herbicide applications are designed to treat visible patches of hydrilla, using a new prescribed herbicide designed to select for hydrilla, allowing surrounding native plants to prosper during treatments.

In conjunction with the herbicide treatment, 500 triploid grass carp will be stocked to eat unseen hydrilla growth, below the surface. The number of grass carp determined to be stocked is the amount needed to replace the estimated portion of the population lost to mortality, restoring the population to the level the lake had in 2019, when herbivory appeared to control the hydrilla. Triploid grass carp were last stocked in Lake Conroe in 2008.

Hydrilla can provide fish habitat in some lakes, but in Lake Conroe, it has a history of forming dense mats that prevent boating and waterfront access to large portions of the lake.  Fortunately, Lake Conroe has a healthy native plant community that provides high-quality fish habitat and improved water quality without impeding water access.

This summer, over 1,200 acres of native plants grew on Lake Conroe, providing fish habitat, bank stabilization, and improved water quality. Controlling hydrilla would allow these native strands to expand further under ideal conditions. Native vegetation and habitat restoration on Lake Conroe is a team effort between TPWD and partners including the San Jacinto River Authority, local anglers, Seven Coves Bass Club, homeowners, and the Lake Conroe Association, who work to plant and promote beneficial native plants.

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