Kauri could be wiped out from the Waitakere Ranges within the next 20 years if the Ministry for Primary Industries doesn't take urgent action, an Auckland community group is warning.
Friends of Regional Parks secretary Mels Barton said she had seen the native trees die off in the Waitakere Ranges for years, and figures released by Auckland Council indicated the problem was getting worse.
Between 2011 and 2016 the spread of kauri dieback disease increased on average from 8 percent to more than 19 percent in the Ranges.
In some areas, including Piha, up to almost 60 percent of trees are infected.
Dr Barton said it was time for urgent action.
"If we don't do something about this now we're going to lose all our kauri, certainly within my lifetime."
The Ministry for Primary Industries (MPI) is the national co-ordinator of the $26 million Kauri Dieback Programme, which was set up in 2014 to try to control the disease.
Regional councils and the Department of Conservation (DOC) are responsible for delivering the programme locally, including making sure hygiene stations for people to clean their shoes are stocked with disinfectant and raising public awareness.
Despite Auckland Council monitoring the spread of kauri dieback in its region, MPI principal conservation advisor Erik Van Eyndhoven said there were no national figures.
"To get out and do surveillance on the many, many hundreds of thousands of trees out there is just absolutely impossible. It's just something we could never do ... we just could not give you that figure, no one could."
Instead, he said they measured the programme's success in other ways.
"The development of new tools to help us manage the disease is a really strong marker, given our strong investment in science and tool development."
Friends of Regional Parks said the Ministry's programme had serious and systemic failings and wrote to Minister Nathan Guy with its concerns.
"MPI are not holding meetings, they're not commissioning research, there's blocks on the funding. Stuff is just not happening," said Dr Barton.
She said more trees could be saved if community groups had funds to teach people how to avoid spreading the disease.
Coromandel Kauri Dieback Forum trustee Viv McLean agreed, and said they had been working hard with what little they had.
Central to the group's success was having a part-time co-ordinator funded through DOC, but that money had run out and the Forum's future was not clear, Ms McLean said.
The Ministry said it would not fund staff but $60,000 in funding was available for community groups to apply for. Dr Van Eyndhoven said three groups were currently getting funding through it.
But Mr Guy backed his ministry.
In a letter to Friends of Regional Parks, he said the level of public awareness of the disease had doubled since 2011, more research was being done than ever before and working with community volunteers remained a priority.
Auckland Council said it would be releasing in the next few weeks a report on the spread of kauri dieback between 2011 and 2016.