The Ministry of Primary Industries is defending its leadership of the kauri dieback programme.
One scientist has been critical of the programme saying, over its nine years, crucial research was never commissioned.
Dr Amanda Black, from Lincoln University's Bio-Protection Research Centre, said the programme was a "trainwreck".
"We've had weak governance around the programme, we've had people involved in managing the programme not knowing how to procure research, not knowing what to look for, and not knowing how to manage it. And we've had some non-delivery in key science areas that has led to the further demise of trees in this forest."
However, the ministry's conservation adviser, Eric van Eyndhoven, said the governance group, which includes Department of Conservation (DOC) and Regional Councils, was advised by scientists.
"I think it's very easy to criticise from the outside, but there's always going to be competing priorities for that [research] funding," he said.
"Whatever we choose to fund there's other things that can't be funded. But in that time we've funded more than 70 projects in full or part so there's a massive effort gone in with the funding we've had available."
The research budget in the early years of the programme was just a few hundred thousand dollars a year, but was boosted in 2014 and now stood at more than $2.6 million a year, Mr Van Eyndhoven said.
Scientists say iconic trees are at risk in Northland's Waipoua Forest because comprehensive soil sampling work has not been done.
Dr Black said Waipoua was in urgent need of a crisis management plan if the big trees were to be saved.
However, Mr van Eyndhoven said the responsibility for soil sampling and other ground work on conservation land and private property lay with DOC and Regional Councils, respectively.
Auckland Council carried out aerial surveys of its kauri forests starting in 2010, followed by soil sampling, and now has clear data on the location and spread of the disease.
The Northland iwi Te Roroa has taken DOC to task for not doing similar detailed work in Waipoua Forest, where kauri dieback is creeping closer to rakau rangatira - revered trees like Tāne Mahuta and Te Matua Ngahere.