Disfiguring fungus hits Chch trees

Press, 20 November 1981, Page 21

Disfiguring fungus hits Chch trees

Many of Christchurch’s plane trees have been attacked by a disfiguring fungus, known as “anthracnose.” The plane tree is common in Christchurch parks, avenues. and private grounds. In Linwood Avenue alone there are 140 specimens. “It is worse this year because of the damp spring. I am surprised at the extent of the fungus but there is not a lot we can do about it.” said the Christchurch City Council’s tree specialist, Mr Walter Fielding-Cotterell. The sometimes-fatal fungus strikes at springtime. The first symptoms are blackening of the tree’s leaves, which then drop off. Many trees recover and grow new leaves which turn brown from the central veins, but these leaves usually stay on the tree. Mr Fielding-Cotterell said that several years ago the Council had had to remove two big diseased plane trees in Cramner Square. Some trees outside the railway station had also had to be cut down after the fungus caused eruptions under the bark and the bark to fall off. Spraying the trees against the fungus was usually impracticable because they were so large and most sprays had proved ineffectual. Mr Fielding-Cotterell said the council might now have' to consider the future of plane trees in Chch. The diseased trees looked bad, he said. “It makes you wonder about the future of the London plane tree." London and Occidental hybrid plane trees were worst affected by Anthracnose, while the Oriental plane tree was more resistant. Mr Fielding-Cotterell said he had known of the fungus for “a few years now.”

Dr lan Harvey, of the Ministry of Agriculture’s plant health station at Lincoln College, said the fungus struck “every few years." It was spread by the rain. This year's low spring temperatures and southerly rain had contributed to the spread of Gnomonia platani, the scientific name for the fungus. Anthracnose was a sporadic disease which attacked the stems and branches of the tree. The last big outbreak in 1976 struck trees at Jellie Park. Dr Harvey said.

On young trees it could cause canker on the branches which could stunt the tree or kill it. A spokesman for the Ministry of Agriculture in Christchurch said that several persons had telephoned with queries about the plane tree fungus. Nurserymen also said that people had brought in plane tree prunings asking about the fungus. But they say that regular spraying has" prevented the fungus affecting nursery specimens.