Environment Waikato hopes to have some control options to the egeria weed problem in Lake Taupo by the end of the summer.
This week’s Biosecurity Committee meeting was told a variety of control methods were being examined to deal with an outbreak of the previously unreported exotic weed in the lake, but staff still needed to work through what might be feasible.
When the problem appeared earlier this year, Environment Waikato considered information from NIWA scientists and decided a wider pool of expertise was needed to resolve the issues. Two workshops had been held in August and October.
All the parties agree that eradicating the weed was not a viable option. Efforts should be made to control its spread, and local stakeholders needed to continue to be involved in the process.
A strong local opinion was that there were wider issues surrounding lake management needed to protect the lake and its environs. Public education was the key to preventing spread of the weed, because it did not produce seed and was almost exclusively spread through human activities taking fragments to new sites.
Its spread could be minimised by ensuring fragments were not transported by boats, trailers, fishing gear and recreational equipment. People needed to be provided with information to co-operate, and signs were needed at nearby lakes to make users aware of the risk of weed transfer. Information pamphlets would be helpful.
If boat users were to be asked to clean boats and trailers, facilities would need to be provided. The use of weed harvesters was also an issue as equipment could spread the weed.
Biosecurity Contracts manager Garth Woodward said the issue at one of the reported sites was sediment inflows, which meant a high sediment load entered the Kinloch marina.
Chemicals could not be used because they tended to cling to sediment, and an earlier attempt to smother the weed with polythene resulted in weed growing on the sediment gathering on top of the polythene.
Use of local dive groups had been suggested to hand weed, and Environment Waikato would pursue this, along with other options.
The Committee decided to erect signs at the weed-free Lake Kuratau, develop a harvesting protocol in consultation with appropriate other agencies and apply any feasible methods to contain egeria.