Spray programmes in Lake Dunstan are having the best effect on weeds in more than 20 years, the lake's enforcement officer says.
Shayne Hitchcock spoke at the Central Otago District Council's community services committee meeting last week, reporting on recreational lake activities between Christmas and New Year.
He said even though weeds such as lagarosiphon were still in some areas, the spray programme had the "best results I've seen in my 21 years in the job".
Mr Hitchcock said this was particularly true at Champagne Gully, between Clyde and Cromwell, and Old Cromwell.
He said boating activity in the Kawarau River between Cromwell and Bannockburn required "extra attention" this year because of the large increase in jet skis and jet-boats and the increase in seasonal workers and holidaymakers with little knowledge of marine operations.
To counter this, two signs warning of other users in the area had been erected at the main river access points.
Mr Hitchcock said in general, the behaviour of boat operators on the lake was good over the period, but he issued 25 written warnings to people disobeying boat rules.