Among the dozens who have lost their jobs at one of Australia's largest tomato production companies is migrant worker Sharon Tarisesei, who says many of her colleagues are feeling apprehensive.

Ms Tarisesei picked tomatoes in the glasshouse at Perfection Fresh, but the detection of the tomato brown rugose fruit virus (ToBRFV) at three farms in the Adelaide Plains last month has left hundreds of her colleagues in limbo.

"Lots of them [are] worried that they're not going to be able to find jobs to make ends meet," she said.

Ms Tarisesei, who recently travelled to Australia from Vanuatu, is a participant in the Pacific Australia Labour Mobility (PALM) scheme, which means she will be guaranteed work at another farm somewhere Australia.

"I've got my mother, my children, my husband and my brothers and sisters — I literally look after everybody," she said.

But she said some of her colleagues had less job security, because they were labour hire workers.

"[There are] lots of questions going through our mind, like what it's going to be like," she said.

"You don't know whether you'll be redeployed to a farm where you'll enjoy working there, like here at Perfection."

Finding work is 'going to be difficult'

Along with Gawler River Tomatoes and SA Tomatoes, Perfection Fresh was recently placed into quarantine by the South Australian government after ToBRFV was detected — with an order for the impacted growers to dump their tomato crops.

The virus does not pose a threat to human health, authorities have said, but can reduce the yield and quality of produce.

The outbreak in South Australia has led to Western Australia and Queensland banning SA tomatoes, while New South Wales is only dealing with businesses in the clear.

On Wednesday, Perfection Fresh announced a "significant number" of jobs would go, after previously warning the SA government that biosecurity restrictions could result in the loss of up to 500 employees.

The United Workers Union's Tim Nelthorpe said there were three different "cohorts" of impacted workers at Perfection Fresh — permanent staff, labour hire workers and participants in the PALM scheme — and that each could be impacted in different ways.

He said more than 200 labour hire casuals at the farm, who are mostly from Afghanistan, Nepal, Cambodia, Congo and Sudan, would lose their jobs in a staggered way over the next two months.

"[For] other people … this is their first job in Australia.

"The union will work with Perfection, with some of our big employers in South Australia to try and find redeployment opportunities — but that won't be possible for some workers, which is why we're calling on the federal and state government to provide some financial assistance."

Mr Nelthorpe said over 200 PALM Perfection Fresh workers from Vanuatu and Timor Leste would be redeployed in coming weeks across Australia, and that the union would fight hard to ensure no redundancies take place among the 200 permanent workers at the farm.

"We expect this to be a short-term, temporary stop of work for [the permanent workers]. Some of them may be stood down and we'd have to work through that if that takes place," he said.

Staff let go 'over staggered timeframe'

Perfection Fresh's chief executive Michael Simonetta previously said the government's decision to shut down its operations was "entirely unnecessary" because the virus had been contained.

"With no timeline for when the lockdown might be lifted, we have no choice but to stand down workers, some of whom have been with us for many years," Mr Simonetta said in a statement.

Opposition leader Vincent Tarzia also called for more support for impacted producers and workers.

"We know that the minister and premier, they have discretion to compensate the producers and employees whenever an order this like is made," Mr Tarzia said.

"It's not good enough to just send those people onto the Centrelink queue."

Premier Peter Malinauskas said the government had to take action because the virus reduces a tomato plant's productivity by up to 75 per cent.

"The responsibility of government is to make sure we protect a $230 million industry," he said.

Primary Industries Minister Clare Scriven said many of Perfection Fresh's workers remained employed for now.

"There is still work at Perfection Fresh in the cucumber side, and also potentially other work in terms of clean-up and so on, so the letting-go of staff is being done over a staggered timeframe," Ms Scriven said.

"The federal Department of Employment and Workplace Relations is meeting with the company … to get a more detailed understanding of the different visa types that some of the workers are on."

The minister said the government had established a support assistance centre for impacted workers, although she acknowledged the centre had not been heavily utilised so far.

"It's not surprising that the very next day there's not a lot of workers there because some of them, many of them indeed, are still employed," she said.

Ms Scriven said her aim was to ensure other states open up to South Australian tomatoes as soon as possible, and that remaining jurisdictions do not close their borders.