Warawara Forest in north Hokianga has been bouncing back after a 1080 poison drop last spring and intensive trapping on surrounding farmland.
But scientists have now confirmed the presence of the kauri killing pathogen phytopthera agathidicida (PTA) around trees on private land in the Puapua area, just north west of the forest.
"The area where we took those three soil samples, two of them came back positive. And the scientist pointed out suspicious brown blotches on the root system, so it doesn't look good," he said.
"I didn't realise how gutting it was going to be when the tests came back positive."
Te Rarawa people have worked hard to protect the forest that Dame Whina Cooper once described as holding the spirit or soul of the tribe.
Much of it is mountainous and inaccessible, and its high plateau where giant kauri grow was never plundered in the logging frenzies that denuded much of Northland in the late 19th and early 20th centuries.
Collaborative effort to fight pests
The iwi is one of the few to support the use of 1080 poison after intensive research and education campaigns by its leaders, and an aerial drop some years ago devastated possum and rat populations on Warawara's steep flanks.
But the ancient forest - with its colonies of native bats, and a remnant rifleman population - is surrounded by farmland, with little or no pest control and the pests soon reinvaded.
Mr Emery said it was sad to watch the decline.
"In the earlier days we could hear lots of kiwi calling at night," he said.
"But as the years passed more and more kiwi have disappeared because of pests - possums, rats, stoats, feral cats and dogs. It was sad to see our Ngahere fall so fast."
In a collaborative effort between Department of Conservation (DoC), nine local marae, Te Rarawa's runanga and the Northland Regional Council last summer, that decline was dramatically reversed.
In September, with Te Rarawa support, DoC paid for a 1080 poison drop over the forests.
Beforehand, Te Rarawa trappers with council support set up a network of bait stations and traps throughout the surrounding area, giving the pests nowhere to go to regenerate.
The 1080 drop, the ongoing pest control, and a brilliant summer transformed the Warawara.
Bronwyn Hunt advises the iwi's kaitiaki trust. She said the forest responded by rolling out a red carpet of rata for the first time in years.
"The kaitiaki (guardians) climb up to the lookout once a year to check the ngahere (forest)," she said.
"This summer, when we got up to the plateau we saw these red sweeps of rata that just covered the canopy of the ngahere, going out into the distance.
"It was incredibly humbling, and we were just so pleased to have that immediate visual confirmation, that possum damage had lessened as the result of the 1080 drop."
Possum numbers are already starting to creep up again in the forest, and DoC ranger Henare Chapman said ground trapping and poisoning was needed on the DoC land.
But the impact of the aerial drop on the rifleman population - the only one north of Auckland - was stunning, he said.
"We could only find 14 birds when we monitored in February 2105.
"But when we went back this year after the drop, we counted 60. That's huge, and there's more that we didn't count because they were outside our monitoring test area."
He suspected possums had been eating not just rifleman eggs, but the tiny birds themselves.
Northland Regional Councillor Joe Carr has championed the Warawara project. He said it was a triumph of collaboration between Maori, DoC, and the council.
The council supplies poison and traps for pest control on the private land encircling the forest, and the iwi finds wages for the trappers.
Mr Carr said he wished the same could be done for Herekino forest a little further north, which he said was dying of neglect, and had been since the late 90s.
"I don't want to comment on the politics of it," he said. "But I look at it and it hurts - I am looking at a dead forest."
The Warawara collaboration has not been without its tensions.
Ms Hunt said she and the iwi's environmental manager Rongo Bentson had both received death threats on social media from people with extreme views on 1080.
"They connect to Te Rarawa, but they don't live up here and they probably don't know what's going on.
"If I could say something to them, it would be come up here and learn from your kaumatua and kuia who are a lot better informed than you are about these matters. And come and have a look at the ngahere while you're at it."
Hunters told to scrub up
But with the discovery of PTA the partners are facing a new challenge.
The Warawara Kaitiaki Komiti has placed a rahui (ban) on people using the Puapua track to the forest, in a bid to limit the spread of the kauri killing pathogen.
The leader of the trapping team, Bobby Proctor, is appealing to hunters in particular to show a clean pair of heels - and wheels.
Last weekend he was handing out special cleaning packs to hunters who took part in the Pawarenga pig and possum hunt.
"It's all we can do, really," he said. "Until they come up with an antidote to this disease.
"Lots of cleaning. Boots, bikes, vehicles. We don't know what's spreading it but I'm thinking maybe bikes." Will the hunters scrub up?
"They're pretty much on board with it," Mr Proctor said.
"They understand it's to save the ngahere, just like they came round to the idea of the 1080 drop. They were worried it would kill pigs and their dogs. But there are still plenty of pigs around."