A COUNCIL investigation is underway into the deliberate poisoning of a 150-year-old gum tree in Adelaide’s northeastern suburbs.

The poison was put into holes drilled into the base of the red gum on Lower North East Rd, Highbury, sometime in the past several months.

A security fence has been placed around the large tree, which is showing significant signs of distress.

Signs placed by council say the old gum was around when “Adelaide streets saw the horse and buggy replaced by the first motor cars”.

“Many generations of Tea Tree Gully residents have enjoyed its beauty but sadly, we do not expect it to survive.”

Tea Tree Gully Council arborist Andrew Nicholls said the tree had about two per cent of its green foliage remaining.

The maximum penalty for damaging trees is $120,000.

Anyone with information is asked to contact the council.