23 May 2019

The Bay of Plenty Regional Council is celebrating the removal of the weed cordon that excluded boats from the Motuwhetero arm of Lake Ōkataina last week.

Two weed cordons were originally erected in Lake Ōkataina to help contain hornwort; one of New Zealand’s worst freshwater weeds, which can grow taller than a 3-storey building (10m).

Example of a weed cordon in operation.

Hamish Lass, Senior Projects Officer at the Bay of Plenty Regional Council said that hornwort was first discovered in the lake in 2010.

“Since then we have invested a great deal of time and resources to contain the hornwort using a combination of herbicide and hand removal.

“The use of the weed cordon at the southern end of the lake, which excluded boats from the area whilst it was being treated, has been instrumental in containing the spread. The fact that we are now in a position to remove it represents a significant step in eradicating hortwort completely from the lake,” he said.

Once hornwort enters a waterway it can very quickly form dense weed beds that outcompete and smother all other freshwater plants. It can block waterways and impact on boating, fishing and other lake uses.

New hornwort plants can form from even tiny pieces of the easily broken stems and cause new infestations when those fragments are carried to other waterways via outflows, birds, fishing equipment and boat movements.

To stop the spread of freshwater pests, Mr Lass is reminding all lake users to CHECK, CLEAN and (when practical) DRY their boat, trailer, prop, fishing and sporting equipment when moving from one waterway to another, anywhere in the Bay of Plenty.

The second weed cordon at the Lake Ōkataina boat ramp will remain in place, to further protect the lake from new weed infestations. For more information visit our website.