Spraying targets unwelcome grass

The noxious pest spartina grass which historically has invaded parts of Tauranga Harbour is once again under attack with a spraying programme beginning this week.

The herbicide Gallant will be sprayed by hand over numerous sites within the harbour by Department of Conservation staff using knapsack applicators from today until December 20.

Spartina, also known as cord grass, is an introduced grass that invades coastal mudflats and high tide zones. The thick grass can trap silt and reduce habitats for fish and wading birds.

The grass, which originated from North and South America, was deliberately planted by farmers during the 1950s and 1960s to bind erosion-prone stopbanks, trap sediment to help reclaim estuaries and for stock grazing. It can be found in wetlands, especially estuaries.

But its extensive root system ruins seafood beds, chokes waterways and smothers other indigenous plant life such as sea rushes.

DOC biodiversity ranger Dan Rapson said this year's annual summer spraying was a joint control programme between DOC and local councils in an attempt to totally eradicate the noxious grass from the harbour. Spraying areas include Athenree, Tanners Point, and the mangroves along Baypark expressway and the Te Maunga-Welcome Bay expressway.

Most of the spraying will not occur near boat ramps or close to residential housing but in some instances DOC will need to go through private farmland to access the control sites, Mr Rapson said.

He said one of the biggest sites being sprayed was a 1.5km stretch of mudflats at low tide near Tanners Point.

He said other methods of spartina control had been tried over the years, both organic and chemical, and included hand pulling the grass, cutting or mowing it, but it easily grows back from root fragments.

"But Gallant has been proven to be the most effective, environmentally friendly eradication method," he said.

Mr Rapson said during spraying signage would be placed at all access points to the treatment sites, and remain in place for at least seven days after the last discharge of herbicide.

Mr Rapson said if anyone saw spartina or other noxious plant pests in and around the harbour they were urged to call DOC on 578 7677 or their local council.