NEWCASTLE City Council is investigating the poisoning of 25 eucalyptus trees near the entrance to Blackbutt Reserve, New Lambton.
Many of the trees, in a reserve off Blamey Avenue, had been drilled and poisoned.
"It appears that the remaining trees have died due to poison being dumped on the ground," Newcastle City Council parks and recreation manager Deb Alterator said.
"All levels of vegetation in this area have been affected, from the canopy to the grass and undergrowth."
Police and the council's compliance team are investigating.
Poisoning trees on public land is a criminal offence and can attract significant fines. That, and the method used adjacent to the creek and bushland, breach the Local Government Act 1993 and the Protection of the Environment Operations Act 1997.
Prosecution can result in a civil conviction and significant fines.