Rust said he was saddened, especially since pōhutukawa were threatened by myrtle rust disease.
"To kill a tree that's already in danger, and such a beautiful specimen, is just despicable in my view," he said.
Rust surmised the "selfish" act occurred because someone thought the pōhutukawa was detracting from a sea view. "I think there's nothing worse than just a bare landscape and the sea. In particular the pōhutukawa is just such an iconic tree and when they're in bloom, they're spectacular."
Rust's concerns were shared on social media, with dozens of people echoing their dismay to his post on the Doubtless Bay Noticeboard Facebook page.
Rust hoped the attention would put off anyone from poisoning a replacement or any other trees.
"There are a few others I would hate to see killed."
The incident follows the poisoning of four Opito Bay pōhutukawa late last year. The trees were responding well to a home-grown treatment by Kerikeri expert Phil Walesby.
The Far North District Council had not yet received a report of any trees being killed on Dudley Crescent, spokesman Ken Lewis said.
Under Section 76 of the Resource Management Act, anyone who damaged or cut down a tree protected under that act without consent could be fined up to $300,000. Similar financial penalties were contained in the Reserves Act.