Ospri lower South Island general manager Vivienne Larsen said the operation, covering more than 2130ha, would complement previous work undertaken to remove 20,000 possums from nearby Mt Cargill.
After several years of pest control at Flagstaff and the removal of 515 possums, numbers were being contained at a low level, she said.
Contractors would begin work on Monday in an area including Swampy Ridge, the Pineapple Track, Flagstaff and Nicols Falls.
The work was expected to be completed by June 30.
The work was essential to Ospri’s mission to eradicate bovine tuberculosis, Ms Larsen said.
"We’re on the pathway to eradicate bovine Tb. We need possum numbers to be at sustained low levels for at least three years."
The control would provide the third year of low possum numbers, as proven by previous monitoring results, she said.
"We know the area is popular for walkers ... we’ve taken great care to mitigate risks to pets."
No 1080 would be used.
Trapping, Feratox and brodifacoum would be used and dogs should be kept on a lead in the operation area while warning signs were in place.
It was likely that would be until the end of June.
The toxins being used posed an "extremely low secondary poisoning risk" to pets, she said.
Bait would be in bait stations or bags and there would be no toxins or traps within 20m or in sight of tracks.
Following the Flagstaff operation, Predator Free Dunedin and the Halo Predator Free project would run a possum control programme to maintain the gains and further reduce the possum population over time, Ms Larsen said.
