Hydrilla is a submerged plant that is found in ponds and freshwater lakes. The plant is an invasive species that originated in Southeast Asia and will quickly grow over other plants species in its area. Hydrilla can grow up to one inch per day, and a single stem from the plant can reach lengths of 25 feet. Dense hydrilla growth can also hurt fish populations by simply taking up too much space and leaving the fish with little open habitat. There are measures you can take to help ensure your local ponds or lakes are not overrun with hydrilla.
Remove and kill the hydrilla manually. Use a heavy dirt rake to collect large clumps of the hydrilla. Cut the stems of the hydrilla with a pair of hedge clippers or a knife. Try to cut as much of the plant free as you can, even small parts of the plant left in the water will grow back to enormous lengths. Use a boat to collect hydrilla that cannot be reached from shore. Pull the hydrilla in close to the boat with the rake, then clip the stems. Grab the hydrilla you cut free and lift it into the boat. Dispose of the hydrilla at a landfill or use it for mulch or compost.
Pour herbicide into the pond or lake. Find an herbicide that is labeled for hydrilla--not all herbicides will kill hydrilla. Many herbicides will also kill other aquatic plant species, as well as local fish populations. Ask a local herbicide specialist or aquatic plant biologist to help you choose the right herbicide. Pour the herbicide into the water close to dense patches of hydrilla. Use a boat to apply the herbicide to hydrilla further away from shore. Read the dosing chart on the herbicide bottle so you do not use too much or too little of the chemical.
Introduce grass carp into the area of hydrilla infestation. Grass carp are ravenous aquatic plant eaters and are widely used in areas of Florida to help control hydrilla. Grass carp can be purchased from commercial fisheries, and you can also catch them yourself in areas where they have already been introduced. The thickness of the hydrilla patches will determine how many grass carp you need to add to the water. Low density areas of hydrilla can be cleared with as few as five grass carp per acre, while thicker density hydrilla may require as many as 40 to 50 grass carp per acre. Start off by introducing a smaller number of grass carp than you think you might need, and allow them to feed on the hydrilla for an entire year. Add more grass carp if the hydrilla is not being consumed at a fast enough rate by the carp.