The easily spread invasive oxygen weed forms dense beds up to several metres deep that clog lake shallows and smother native plants.
Lake Wanaka lagarosiphon managers committee spokesman Russell McGeorge said the lake weed was well under control at all sites north of Roys Peninsula, and in Paddock Bay.
A management and control programme of lagarosiphon was implemented in 2005 for Lake Wanaka.
There is another seven years left to run on its 10-year term of control containment.
"We've given high priority to controlling the weed's spread north of Roys Peninsula and we're on track to achieving this. It's at the point where hand-weeding is all that is required to keep regrowth in check at these sites," Mr McGeorge said.
Results were also encouraging at other weed control sites in Glendhu Bay and Stevensons Arm, he said.
Lake users are being reminded to check and clean their recreational equipment and boats to ensure weed fragments are not transported to other waterways.
Hand-weeding and suction dredging are two methods used to keep the weed in check.
Applications of the aquatic herbicide Diquat are used to knock down dense infestations to manageable levels.
The control work is carried out by Land Information New Zealand.
