Hydrilla (hydrilla verticillata)
Hydrilla is a submersed plant. It can grow to the surface and form dense mats. It may be found in all types of water bodies and typically will grow most readily in water temps above 68 degrees.
Hydrilla stems are slender, branched and up to 25 feet long. Hydrilla's small leaves are strap-like and pointed. They grow in whorls of four to eight around the stem. The leaf margins are distinctly saw-toothed. Hydrilla often has one or more sharp teeth along the length of the leaf mid-rib. Hydrilla produces tiny white flowers on long stalks. It also produces 1/4 inch turions at the leaf axils and potato-like tubers attached to the roots in the mud.
Hydrilla forms dense mats of vegetation that can interfere with aquatic recreation and destroy fish and wildlife habitat. Hydrilla can spread in a variety of ways including reproduction by fragmentation, seeds, tubers, as well as turions which is overwintering of buds. One square meter of hydrilla can produce up to 5,000 tubers. Once established, it readily spreads by waterfowl and boating activities. It can very quickly take over a lake or pond if left unattended.
As with most lake weeds, there are four main methods for eradication, water drawdown, physical removal, biological control with “grass eating carp” or microbials, as well as chemical treatment.
If possible a water drawdown combined with physical removal of dead vegetation is a good method to start with and that may be all that is needed.
The second option are “grass eating carp” or Chinese grass carp. You can find out more about these types of fish online or through your local game and fish or county extension agency.
If water drawdown is not an option and you would like a fast and easy result chemical treatment is a safe and effective alternative.
If infestation is fairly thick, rake out or break up mats of the weeds before applying herbicide, so that the chemical can come in contact with the weeds' foliage. Rake out again when weeds have died back.
When using liquid herbicides, thorough coverage of the weeds' foliage is necessary for good results. Inject underwater with a pressure sprayer for foliage beneath the surface. Apply on a calm, sunny day. Do not treat if rain is expected within eight (8) hours.
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