South Australian authorities are reviewing import entry requirements for mangoes after a spate of Queensland fruit fly incursions over summer.
A trade ban has been lifted on one far north Queensland mango farm after an investigation revealed hail damage was the most likely cause of the breach, but investigations are continuing around three other separate incidences since December.
Queensland's general manager of plant biosecurity Mike Ashton admitted the spike of detections in South Australia had surprised authorities and reinforced the need for mango growers to remain vigilant.
Mr Ashton said it was too soon to know the cause of the outbreaks which had collectively resulted in more than 10,000 trays of mangoes to be recalled.
It had been a "particularly bad year for fruit fly", he said.
Up until December, only four Q-fly cases had been found since 2013, with the introduction 15 years ago of pre-harvest treatments for all mangoes destined for 'fruit fly-free' markets being credited for the extremely low rate.
Mr Ashton said current pre and post-harvest chemical treatments were designed to achieve a 99.997 per cent mortality rate, or three survivors in 100,000 fruit flies.
"It's not 100 per cent effective. If the level of infestation in the field is high then there is potential for failure and it's possible that's what happened in this case," he said.
"The second one was related to a hot water treatment used by an organic grower, where obviously chemical treatments aren't appropriate in those circumstances. That's (also) being investigated."
Industry denies growers 'dropped the ball'
The Australian mango industry has defended its growers and moved to reassure its domestic and international markets of its ongoing commitment to strict export protocols.
Pre and post-harvest chemical treatments are an entry requirement for all fruit fly-carrying produce sent to South Australia and parts of Victoria, where multi-million horticultural export industries depend on maintaining 'fruit fly-free' status.
Chief executive of the Australian Mango Industry Association Robert Grey said the mango industry had a very thorough process for dealing with fruit fly, both in the field and in the packing sheds prior to shipment.
"I don't think the industry has dropped the ball."
Mr Grey said the South Australian market accounts for around ten per cent of Australia's mango business, but the flow-on effects of fruit fly to that state are critical.
"The South Australian production region is one of the largest for [crops] like grapes, citrus and stonefruit, and they all really on that fruit fly-free [status] to access a range of international markets," he said.
"So while we are very focused on maintaining access for our mangoes into South Australia, we're also very focused on doing our bit in terms of keeping pests away from areas that don't have them."
SA flags tighter on-farm measures
Biosecurity South Australia has moved swiftly to ban the sale of hail-damaged fruit from Queensland in SA.
"We [usually] get a very small number of infected consignments once or twice a year, but this time there have been five," chief plant health officer Geoff Raven said.
Of the five infected consignments, one was detected by the importer and the other four were reported by members of the public.
"In the three investigated, they all seem to be associated with bad hail events, which causes blemishes and can impact on post-harvest inspection," he said.
Authorities in SA have also asked all fruit importers to step up their checks for incoming fruit and are also reviewing the protocols under which Queensland farmers can export mangoes to SA.
"We will critically evaluate the efficacy of that arrangement, that protocol, to determine if it meets our import requirement and if there are any gaps," Mr Raven said.
"That protocol involves pre and post-harvest treatment inspection. There are a number of steps there to prevent fruit fly larvae being present in mangoes sent to SA.
However, Mr Raven denied the review of the current export protocols indicated the current biosecurity system was flawed.
"When you have any non-conformant, you invoke corrective action and introduce things to prevent recurrence," he said.
He said while some changes might be needed, the strength of the system was the responsibility it placed on farmers to be fruit fly-free.
"It's not particularly easy to police, which is why we set the system the way it is," Mr Raven said.
"The exporters from Queensland, the farmers, know if we find fruit fly it will shut down their business and lead to bad press for them.
"That has happened in this and other cases, so they know they have to follow their procedures.
