The Cabinet has approved a $30 million programme to attempt to eradicate the southern saltmarsh mosquito around the Kaipara Harbour, Associate Biosecurity Minister Marian Hobbs announced today.

"This exotic mosquito, a known vector of the Ross River virus, is a real nuisance and is particularly vicious and aggressive, biting during the day," Marian Hobbs said. "We have yet to have a case of New Zealand-acquired, mosquito-borne disease in this country and this eradication programme will help to keep it that way.

"We're encouraged by results from a SSM eradication programme on the North Island's east coast and we expect a similar outcome from the Kaipara programme."

Around $30 million will be spent over the next four years developing and implementing a plan to eradicate the exotic mosquito from the Kaipara area, which covers a potential habitat of 2710 hectares.

The programme will involve aerial and ground spraying, using S-methoprene, an insect growth regulator that stops the mosquito pupae hatching into adults, and the biological spray Bti.

The mosquito lays its eggs on vegetation just above the waterline but wetting is vital for the eggs to hatch. High tides, heavy rain and wind that increase the size of waves can all encourage hatching.