Councils target invasive aquatic weed

The lake at The Groynes Reserve, where weed eradication efforts are set to begin.

A chemical treatment that is harmless to fish and plant life will be used this week to eradicate an invasive weed choking lakes in The Groynes.

The weed, lagrosiphon major, which forms dense mats of vegetation, has affected lakes at the popular recreation reserve since 2014.

There has been concerns that the annual Take a Kid Fishing day, set to be held at the The Groynes in October, might be postponed because of the weed infestation. The city council commissioned environmental consultants Boffa Miskell to undertake a report which recommended using the chemical Endothall to fully eradicate the aquatic weed.

It found the herbicide had no known negative impacts on native fish and plants. The reserve’s fishing lakes were closed on Thursday and will reopen on August 23.

The weeds will be removed by a mechanical harvester six weeks after the spraying.

Environment Canterbury’s regional biosecurity team is working closely with city council staff on the project.