Spraying to eradicate invasive spartina grass

Signs on the banks of the Taruheru River yesterday were to alert people to the spraying of herbicide to eradicate spartina grass.Picture by Liam Clayton

Herbicide spraying starts today on the spartina grass along the edges of the Taruheru River.

It is the first stage of a Gisborne District Council project, in collaboration with mana whenua, to get rid of the invasive spartina weed from the inner-city waterway.

GDC sustainable futures director Joanna Noble said members of the council’s biosecurity team would spray the grass at low tide, along the Taruheru River between the Marina Park boat ramp and the Peel Street bridge.

“The spraying will take around three hours.

“People are advised to avoid the area during the spray times which are between 10am and 3pm.

“It’s also weather-dependent and requires a dry day with minimal wind.

“We hope to complete this first stage of the spray on Friday.  However, Saturday and Sunday are alternative days if the weather doesn’t end up suiting on Friday.”

Ms Noble said testing and analysis of the water was done earlier this week and would be done again after the spray to monitor changes to the river’s ecology.

The herbicide Haloxyfop-methyl is being used, in compliance with the Environmental Protection Authority’s permission for the use of substances to control aquatic pest plants.

Spartina alterniflora and Spartina anglica are the two species of spartina introduced and planted in the Taruheru River in the early 1900s. It was planted to stabilise and bind stopbanks.

However, more than 100 years later it has taken over the waterway and left no space for native plants and wildlife.

“Spartina’s ability to form in dense clumps and trap sediment causes the ground level to rise affecting the waterflow, native inhabitants of ecological zones and increasing the risk of flooding.”

Ms Noble said historically the Taruheru River was a thriving ecosystem, where there were natural mudflat areas bounded by salt marsh and riparian vegetation.

“Eradication of spartina will enable native fauna and flora to reoccupy tidal areas lost to this invasive grass.

“This work is likely to deliver flooding benefits and significant environmental, social, and cultural benefits.

“With the spartina gone, tidal flushing will increase which will improve conditions for native species such as mud crabs, fish, shellfish, and wading and native birds.

“The project also includes replanting native plants along the Taruheru to improve the biodiversity of this area.”

For more information, follow the Facebook page Haumanu Tū Ora   or visit the council’s website.