It could be up to six years before new ways of killing possums become a practical reality, scientists say.
The poison 1080 is used extensively in New Zealand to control pest animals in native ecosystems and agricultural land, but its use is becoming less acceptable to many people.
Landcare Research possum biocontrol development programme leader Dr Janine Duckworth said in a Science Media Centre briefing different fertility controls were being researched as an alternative to the "boom and bust" of present possum controls.
It was hoped if a control could create 50% sterility in a population, the time between control work could be extended up to 12 years.
"This would be part of an integrated pest-management system."
Controls being investigated ranged from ways to interrupt fertilisation to a vaccine based on the smallpox virus.
It would take between two and five years "minimum" for these options to be ready to field-test, she said.
However, the future of this research was uncertain with funding ending on September.
Connovation Ltd director of research Dr Charles Eason said work was being done to extend the registration of low-residue poisons, to bring in toxins used overseas, to develop new toxins more favourable to the New Zealand and Australian environments and find smarter ways to deliver the toxins.
But it could be three to six years before a viable alternative to 1080 was available, he said.
Any new pest control product had to go through the lengthy New Zealand Food Safety Authority and the Environmental Risk Management Authority approval process.
"It's a huge challenge."
Work on the "designer toxin" para aminopropiophenone (PAPP), which targeted stoats, could be approved in a "crude bait" form in the next six to 12 months, he said.
However, it would then need more field research.
Other alternatives being researched included a pelleted cyanide, a control considered more humane which carried less risk to dogs.
It was in the process of becoming registered for use to control wallabies.
Zinc phosphide was another option used overseas being investigated for possum control in New Zealand, he said.
Also being researched were sodium nitrate, which was being tested for possum and feral pig control, and low-dose vitamin D.
Lincoln University wildlife management senior lecturer Dr Shaun Ogilvie said his research was at the "beginning of the conveyor belt", as it was looking at naturally occurring toxins in New Zealand plants and their potential for pest control.