Red eared slider turtles are sold in pet shops, but are listed as one of the world's 100 worst invasive species.

A Christchurch woman who sneaked a tiny red-eared slider turtle into New Zealand faces sentencing for a breach of the Biosecurity Act.

The turtle is listed as one of the world's 100 worst invasive species.

The turtle had been given to 43-year-old Qiang Wei Luo's 6-year-old son on a visit to family in China.

Luo knew it could not be brought into New Zealand, but she decided to bring it in when her son became upset.

The Waltham woman, who is a New Zealand permanent resident with a Chinese passport, pleaded guilty in the Christchurch District Court on Thursday to a charge of possessing unauthorised goods under the Biosecurity Act.

The Ministry for Primary Industries told Judge Tony Couch that New Zealand was one of the few countries without an established wild population of red-eared slider turtles.

The species was readily-available in New Zealand through pet stores and over the internet.

Their impact was largely unknown, but they could affect aquatic plants, insects, small fish and ground nesting birds.

While Luo visited her parents in China in December, her mother bought two turtles and gave one to her son.

Luo knew it could not be brought into New Zealand, but after her son became upset she put it in a container in his backpack.

When she was interviewed later, she said she hoped the turtle would be found at the border so it would be someone else, and not her, taking the turtle from her son.

She did not mention the turtle when questioned as she arrived in New Zealand. It was not found when their bags were X-rayed. The turtle was about the size of a thumbnail.

She took the turtle home to Christchurch where it was found on February 1 when ministry officials arrived for an inspection. The turtle was seized and a veterinarian humanely euthanised it.

The husband and wife cooperated with the investigation and showed remorse.

The ministry asked for $61 reparations – the cost of euthanising the turtle.

The turtle is seen as a medium category pest. Three regional councils in Auckland, Waikato and Wellington control the turtles in their pest management plans. The turtles are prohibited imports.