Cutting back lake weed in Lake Dunstan followed by spraying the regrowth has been "very successful'' in controlling the pest plant, the Central Otago District Council heard this week.
Boffa Miskell Ltd carried out lake weed control for Land Information New Zealand and biosecurity project manager Marcus Girvan said the lagarosiphon weed had been cut 1m-1.5m below the lake surface at numerous sites in December.
The prolific regrowth was then sprayed with herbicide in mid-February.
Central Otago Mayor Tony Lepper said he watched some of the weed-cutting and it seemed "a lot of effort for very little gain''.
Mr Girvan said cutting it back set the weed up for a "good hit with herbicide'' as the young, green regrowth was particularly susceptible to sprays.
A year ago, lake harbourmaster Shayne Hitchcock told the council flourishing weed in Lake Dunstan was a safety issue.
Eradicating the weed was impossible but more attempts should be made to control it at high-use recreational spots, as safety was important, he said.
Since, a Guardians of Lake Dunstan group has been formed and a new 10-year lagarosiphon control strategy discussed.
In a report to the council about boating on the lake over the summer, Mr Hitchcock said the lake weed was "still being a huge problem'' around the Old Cromwell foreshore.
It caused a decrease in recreational lake users around that area.
"A boat cannot access the beach without the prop dragging through the weed. Very unpleasant for swimmers and water-skiers, wakeboarders and people on and off biscuits.''
