Large r¯at¯a may be first in NZ to contract deadly disease
Scientists are testing tissue from a protected tree in central Christchurch to examine how it became infected and whether it could have succumbed to a fungus that has decimated native trees in Hawaii.
The large southern ra¯ta¯ on Cambridge Tce, on the banks of the Avon, appeared to die suddenly last month, prompting fears it may have fallen victim to disease.
Christchurch City Council staff are investigating the cause of its demise – though there are questions over whether it may still have life in it after green shots were spotted. An arborist told locals a trench that was dug nearby may have damaged it.
Specialists at the Ministry for Primary Industries (MPI) are also testing plant tissue and soil samples from the tree to determine whether it could have been affected by ceratocystis fimbriata, a disease not yet found in New Zealand.
The disease is a fungus known to have attacked a wide range of plants and trees around the world. A major outbreak in Hawaii in 2015 led to the death of hundreds of thousands of o¯ hia, the American state’s most abundant native tree, which belongs to the family of New Zealand’s po¯ hutakawa and ra¯ ta¯ .
The fungus kills trees within days or a few weeks. While there are concerns about the Cambridge Tce ra¯ta¯, which appeared to die quickly, scientists say initial signs suggest it was not killed by ceratocystis fimbriata.
A spokeswoman for MPI said: ‘‘MPI’s laboratories have received plant tissue and soil samples from the tree, and testing is under way to determine the cause of the dieback. The ministry is testing for a number of diseases, one of which is ceratocystis fimbriata. The symptoms, however, are not consistent with C fimbriata infection and our initial examination of plant material did not find any evidence of this fungus. We expect to have more information within the next 10 days.’’
Council operations parks manager Al Hardy said the tree was planted in 1950 and had been previously inspected twice. He was unsure how it died. The tree is not listed as being notable, but is protected due to its size.