A big 1080 drop has taken place in Golden Bay to try to stop possums spreading bovine tuberculosis to cattle and deer herds.
TB Free New Zealand carried out the operation, which saw about 10 tonnes of 1080 dropped over 7000 hectares of hill country.
The organisation's northern South Island programme manager, Matt Hickson, says the operation targetted an area where possums are suspected to be carrying TB.
"Currently there's no herds in that area that are infected with TB, but we very strongly suspect that there is TB in the possums within the Kahurangi National Park.
"So the area was part of our boundary control to stop movement of possums and the disease from the Kahurangi into those areas where they can interact with cattle."
Mr Hickson says the aerial 1080 operation will be complemented by a ground operation, focusing on farms and the boundary of the Kahurangi National Park.
He said 1080 is highly toxic to dogs and he urges dog owners to keep their pets under control at all times near Kahurangi National Park or out of the area all together.