A number of residents have reportedly been targeted by a pair pretending to be biosecurity officers, spraying for fruit flies.

Biosecurity New Zealand said it was aware of a report made by north Auckland residents that a man and a woman had visited their homes with a spray bottle.

On Wednesday, a man and a woman were said to have entered a North Shore property, after calling out to see if anyone was home first.

"They came through our side gate to the backyard and found my husband there, so they told him they were there to spray for fruit fly," a post on the public Birkenhead and Northcote Community Facebook page said.

"The man then gave our Puka tree (not a fruit tree) a couple of squirts with a spray bottle before leaving."

According to the post, only the day before official Biosecurity New Zealand officers with ID had visited the address. 

Other people said the pair had also visited their properties in Birkenhead and Northcote.

Biosecurity New Zealand placed legal controls on the movement of fruit and vegetables in Devonport and Northcote in February, after a Queensland fruit fly was collected from a trap and identified.

The Queensland fruit fly can have damaging effects to New Zealand's agriculture and horticultural industry.

A Biosecurity New Zealand spokesman said it was aware of the post, but had received no other reports of people posing as biosecurity officers.

While biosecurity response activities were being carried out, he said Biosecurity New Zealand had been in contact with community police officers in the Northcote and Birkenhead areas to ensure the safety and security of properties.

"Individuals posing as biosecurity officers could potentially hinder our work by undermining trust in our response teams. We rely on community support to help eradicate this pest," the spokesman said.

Biosecurity New Zealand said its workers were "clearly identifiable" in their uniforms or in hi-visibility clothing branded with "Biosecurity Response". 

Their workers also carried photographic ID stating they were working on the Queensland fruit fly response.

"When visiting a property, Biosecurity New Zealand staff make contact with the homeowner when possible, and provide a full explanation of why they are there," the spokesman said.

"We provide written information that explains the purpose of the response, who has been on the property and when, and what activity is being undertaken."

A police spokesman said it was not immediately aware of reports of Biosecurity New Zealand imposters.

He said police were aware of people in the past who had tried to scam residents by posing as tradesmen, survey workers and cold callers.

Anyone who had witnessed suspicious behaviour was encouraged to contact the police.

To prevent being targeted, homeowners could secure their properties with locks and gates and by keeping "attractive items" out of sight. 

People should also note any suspicious activity and check the ID of any people claiming to be workers or tradesmen.