Eradicating the exotic lake weed egeria from Lake Taupo is not feasible – but preventing its spread to other lakes can be done, Environment Waikato has been told.
Scientists from the National Institute of Water and Atmospheric Research gave Council’s Biosecurity Committee options to manage the weed which is beginning to invade the lake. Paul Champion and Rohan Wells told the Committee that four exotic water weeds were widespread throughout the Region, except for the upper part of the catchment.
Lake Taupo has all four weeds – lagarosiphon, hornwort, elodea and egeria. Lake Rotoaira has all except egeria, Lake Otomangakau has all but hornwort and egeria and Lake Kuratau has no introduced exotic weeds. Egeria is limited to Taupo Harbour and Kinloch Marina but has the potential to spread to sheltered and nutrient enriched areas, such as Acacia Bay and Two Mile Bay.
It could be contained using a weed cutter, herbicide such as Diquat, a suction dredge operation and having a washdown area for boat trailers.
The scientists suggested using Diquat for the Taupo Harbour and continue harvesting in the Kinloch Marina. Mr Champion said it was important to think about protecting Lake Kuratau by preventing access and banning motorised boats and anchors, and protecting Lake Otomangakau by inspecting boats and equipment.
He said it was important to educate boaties on boat hygiene and the effect of these weeds on Waikato water bodies, as well as how they were spread.
The Council is to get a report from staff on cost benefits of the different options and options for protecting waters so far unaffected by the weeds.
Cr Jim Howland told this week’s Council meeting that the report showed the Council was right in waiting to act until it knew more about the weed, or it would have been “doing the wrong thing for the rest of our lives”.
Cr Murray Black said the Council had been criticised because it did not act immediately which had been proved to be beneficial in this case. Chairman Neil Clarke said the results showed the merits of making sure the situation was clearly understood before rushing into action.