Biosecurity Tasmania acting general manager Rae Burrows provided the update on fruit fly testing as part of budget estimates on Thursday.

Tasmania is considered fruit fly free, but testing continues on imported fruit as it comes across the border.

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Ms Burrows said last year larvae was found in passionfruit and had also been found in raspberries, which had been previously categorised as low risk host fruits. More frequent checks were being done on stone fruit and mangoes imported into Tasmania.

She said increased testing started 12 months ago as part of the Securing Our Borders initiative, to respond to the growing threat of Queensland fruit fly.

"We started this 12 months ago and the idea was to increase 600-count inspections at the border because we were aware that the risk of Qfly entering Tasmania had increased, particularly as we had just eradicated the North-West and the North of Tasmania and Flinders Island from Qfly, as you're well aware," she said.

Last year, Biosecurity Tasmania staff undertook 4147 inspections at the border. A total of 1.8 million individual pieces of fruit were inspected by staff, many of whom were seasonal workers.

Ms Burrows said there was a particular focus on mangoes because that is where they were getting the most detections from. More than 137,000 individual mangoes were tested on arrival in Tasmania.

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"I have to compliment my staff. Some of these are seasonal staff, who come on for the securing our borders initiative. They pick up the piece of fruit and they are looking for sting marks. We are talking about a needle-point mark on the fruit. Unless the fruit looks a bit gungy, that's what they get," she said.

There have been two detections of fruit fly larvae in Tasmania in 2020 but neither is considered an outbreak.

Ms Burrows said over the testing period, staff detected 431 pests and diseases. Some of which were fruit fly.

She said the detection of larvae in passionfruit "was a worry" because it had never been considered a high risk fruit. Both passionfruit and raspberries have had their risk profile updated in response.