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Published: 2003-07-16 00:00:00

Environment Waikato, in close collaboration with DoC plans to eradicate the coastal plant pest spartina within 10 years in most Waikato areas.

This week’s Biosecurity Committee heard eradication is likely to take 20 years in Kawhia and Aotea Harbour where there are extensive patches.

Department of Conservation representative Rachel Kelleher outlined the work DoC is doing to control the weed in the West Coast and Coromandel harbours. Environment Waikato is contributing by monitoring the consents, which were required to use herbicides in the coastal marine area, and paying up to 30 percent of the control costs in any given year.

Ms Kelleher said spartina was introduced to stabilise tidal areas and as a stock feed in inter-tidal areas – which was now considered environmentally unacceptable. Many groups, including the Agriculture Department until the 1960s, encouraged its use.

Spartina is a grass and grows up to a metre tall, taking over large areas of estuaries and resulting in loss of natural habitat for wading birds and fish spawning sites, damaging recreational fisheries and seafood sources and causing navigation problems.

Doing nothing about the pest had been considered, but this would damage biodiversity and regional conservation values over 7,000 hectares in the Region so eradication was the preferred option.

Spartina caused biological changes in estuarine areas and was now widespread in Raglan, Aotea, Kawhia, Manaia, Coromandel, Tairua and Whangapoua harbours and in the, Firth of Thames and Waikawau Bay.

Most infestations were still under a hectare, which is why it was considered preferable to eradicate it while it was still manageable.

The herbicide Gallant™ was being used because it targeted grass species only and was being spread by helicopter, air boats and knapsack sprayers. Areas under mangroves were a challenge, she said.