Dunedin City Council community and recreation services manager Mick Reece was asked about the fate of the trees at yesterday's community development committee meeting.
The Otago Daily Times yesterday reported it was feared all 16 of the plane trees were threatened by an as-yet unidentified fungal root disease, after four failed to come into leaf this summer.
Mr Reece told councillors yesterday staff were anxiously awaiting the test results of samples taken from the trees, which were due next week and were expected to confirm suspicions the trees were being attacked by disease.
Concern was growing the longer the trees failed to show signs of life, but the situation would not be an "emergency" until the exact type of disease was confirmed by test results, he said.
"We think we are in trouble. We hope we are not, but the longer it goes on it's becoming obvious these trees are not just going to break into life.
"Something is happening to these trees that's not happened before."
On Monday, Mr Reece said the worst-case scenario was confirmation all 16 trees were afflicted by the plane tree equivalent of Dutch elm disease, which devastated elm trees in Europe and the United States last century and was found in Auckland in 1989.
The plane trees have lined the Octagon's central carriageway since 1891, and had a long history of problems with anthracnose, considered the "common cold" of trees, he said.
However, an "unmanageable" new disease could result in all 16 plane trees being removed and replaced with another type of tree, he said.
The trees usually came into leaf in November, but four had failed to do so this summer and showed little sign of life despite regular rainfall and pruning, he said.
Other trees within the Octagon were also showing signs of the disease, as were trees in George St, near Knox Church, and Princes St.
