By TONY GEE
Choking oxygen weed in Northland's biggest lake will be sprayed with herbicide within two weeks as part of a plan to control the problem.
The regional council is seeking tenders from contractors to carry out the work at 1200ha Lake Omapere, near Kaikohe.
The programme also calls for 20,000
weed-eating grass carp to be released into the lake to further reduce and control weed growth.
A diquat-based herbicide initially will be spread over 12 per cent of the lake, either in gel form from a helicopter or distributed under the water from a boat so it sinks on to the weed.
That would be repeated on another part of the lake if necessary, regional council monitoring manager Tony Phipps said in a report to the Far North District Council, which is paying part of the cost of the clean-up project.
The carp will be released after all spraying is completed, and will join other carp introduced into the lake last year.
Many of the fish in the earlier release are believed to have been eaten by shags.
Mr Phipps said the lake weed, egeria densa, was healthy and growing, but had not yet reached the rapid growth rate of last spring and summer.
Because of this, there was still time for an effective control programme.
At one stage the rapid growth and density of the weed threatened to "collapse" the lake.
A National Institute of Water and Atmospheric Research scientist, Dr Paul Champion, is being brought in as principal scientific adviser for the project.
The regional council hopes a contractor can start spraying the lake before Christmas.
