"We're stepping in to take over."
Mr Martyn said the planned drop was in the north of the district in rough and hard to access areas where ground control options would not be possible or effective.
It would the council's first 1080 drop in more than a decade and would be voluntary for landowners.
Mr Martyn said Horizons would have to wait to see is it had enough support to make the drop effective.
The use of 1080 faces some opposition in New Zealand and executive director of animal rights group SAFE, Hans Kriek, said there was no dispute 1080 was an inhumane way to kill animals.
"We're an animal rights group so we look at it as an animal rights issue. Purely from that aspect we are opposed to it," he said.
"We know that 1080 is an inhumane was of killing animals. I've seen video of animals dying from 1080. There's no New Zealander that would find it easy to watch."
But Mr Kriek acknowledged that in some terrain there were few options so he would like to see more effort and research put into alternatives.
"For the foreseeable future we can't really see them using anything other than 1080 in those areas but is that what we want to do for the next 50 to 100 years?
"I think in the short term there is probably very few options available. In the long term we definitely want to get people in authority to look long term.
However, Forest and Bird lower North Island regional conservation & volunteer manager Amelia Geary supported Horizons picking up OSPRI's work and the use of 1080.
She didn't share SAFE's concerns and said the use of 1080 was also backed by the Parliamentary Commissioner for the Environment.
"It's an important tool in keeping possum numbers down and protecting the bush. We're pretty glad that Horizons have picked this up really."