ENVIRONMENT

400-year-old Chinese banyan tree in Kowloon Park saved from the chop

After surviving for four centuries, a banyan infected with brown root rot has been saved from the chop and is part of a treatment trial

PUBLISHED : Monday, 10 November, 2014, 6:46am
UPDATED : Monday, 10 November, 2014, 5:41pm

A 400-year-old tree in Kowloon Park has been saved from the chop and is now part of a trial to test a possible remedy for brown root rot disease.

The Leisure and Cultural Services Department overturned its earlier decision to remove the Chinese banyan, which is suffering from the infectious disease affecting trees across the city.

The Tree Management Office said the trial would cover three other heritage trees: the Lam Tsuen Wishing Tree in Tai Po; a banyan in Lei Yue Mun Park, Shau Kei Wan; and another banyan in Shui Mei village playground, Yuen Long.

The 400-year-old "king" of the city's trees had been on a removal list since August last year after fungus from brown root rot was found on its trunk. There is no proven treatment for the disease.

Advisers from the tree office said at the time the "painful" decision had been taken to prevent the spread of the disease.

But the department last week told the Post that the tree - which is under its management - has been kept to try out a new treatment. A spokeswoman said: "The tree has shown signs of improvement since April. Given its historical value, it has been retained for a trial … with a view to salvaging the tree as far as possible."

The U-turn has sparked debate among tree experts, with one questioning the trial method and warning the disease might spread if the tree is not destroyed.

"It is understandable that the government wants to save it as far as possible, but the trial itself is unscientific," said Professor Jim Chi-yung, a University of Hong Kong academic and a member of the expert panel at the tree office.

The office said that under the trial, microfungi named Trichoderma had been applied in the soil around the root zone since August. It said the trial aimed to test the effectiveness of the microfungi in suppressing the fungus that causes the disease.

But Jim said the trial was not being conducted in a controlled environment, meaning any change in its conditions from the microfungi could not be proven.

He also warned that spores from the fruiting bodies of the disease could be released and carried by the wind, rain and animals - spreading the problem elsewhere in the city - if affected trees were not removed.

Jim and Ken So Kwok-yin, who is also on the expert panel, said the office had not consulted them on how to conduct the trial.

So said a tree with brown root rot had shown improvement in the microfungi trial but later died. The office confirmed a Chinese hackberry tree in Kwai Chung involved in the trial was chopped down, but would not say why.

Nevertheless, So said: "This is the biggest banyan … we have no choice but to take a chance."

The trial will run until the end of next year, the office said, adding measures had been taken to minimise the spread of the disease. Lam Tak-chak, of the Trees Conservation Association, said an independent arborist should be brought in to assess the tree.