Once hydrilla has been introduced into a lake, complete elimination is very difficult. There is no quick fix for hydrilla but control options fall into three basic categories:
Remove part or all of the plant either by hand or machine (harvesting)
This is costly and the plants grow right back, like mowing a lawn.
Dispose of all plant fragments on shore: Because new plants can sprout from fragments, all plant material cut or collected MUST be removed from the lake. Throwing hydrilla back in the lake can result in a maximum fine of $2000 per plant.
Winter lake lowering to expose the plant to drying and possibly freezing temperatures
This only impacts plants in less than 12 ft of water, and doesn’t kill roots
Introduce fish (sterile grass carp) or insects that eat the plants
Reintroduce native plants- the City has done this on 20 sites on Lake Austin and Lady Bird Lake, but it takes a long time for the plants to outcompete invasives like hydrilla
Chemical control using aquatic herbicides to kill the plants. Lake Austin’s depth and constant water flow limit the effectiveness, and due to drinking water intakes and public perception, it has not been an acceptable solution in the past. The City does not recommend this, and private individuals must get approval from TPWD for this action.