There are fears the price of tomatoes may rise with a third grower infected in the latest virus outbreak.
As supermarkets placed two-carton restrictions on eggs during the avian flu emergency, some consumer groups are already tipping tomatoes may be next.
The devastating tomato brown rugose fruit virus has been confirmed in a third "commercial business" in a key growing region just outside Adelaide to spark the latest scare campaign.
The virus had never been detected in Australia before.
South Australia's Primary Industries and Regions department has been charged with steering the immediate response to the find in the North Adelaide Plains.
Infected imported seeds are believed to the source of the outbreak.
PIRSA this week confirmed the third discovery but also went public with a warning.
"... PIRSA is undertaking extensive tracing of seed lots to try and identify the source of infection, which remains unknown at this stage," the department said on Thursday.
"Tracing has shown some other states may have also received potentially infected seed, and these jurisdictions have been informed and are conducting follow up testing."
Like the bird flu outbreak which spread rapidly across Victoria from a central supplier, it is feared the tomato virus could do the same.
New Zealand was quick to ban Australian tomato imports and Queensland and Western Australia have followed with South Australian bans.
New Zealand growers remain fearful.
One farm leader claimed the South Australian outbreak was linked to a "a very large propagator that sends tomato plants all around South Australia where the infection has been found and in other states".
PIRSA said the third detection of the virus was "linked through the movement of plant material to known infected sites on the Northern Adelaide Plains".
More than 2000 plant samples have been taken for testing from 18 businesses, encompassing 84 greenhouses.
"Response activities, including surveillance and tracing measures, have been underway since the first detection was confirmed on August 5, and PIRSA continues to work closely with affected businesses," the department said.
"Three businesses are also being followed up in case of infected seeds, with PIRSA undertaking extensive tracing of seed lots to try and identify the source of infection, which remains unknown at this stage."
Listed as a National Priority Plant Pest in Australia, the virus is said to be highly contagious and is regarded as a "considerable threat" to Australia's $5.8 billion vegetable industry due to reduced yield and quality of produce.
The virus has no known effects on human health.
The PIRSA update also said "no shortages of tomatoes or price rises are expected at this time as a result of these detections" although some growers say this depends on whether the quarantines were in time or the virus had already spread to other states.
Infected plants show symptoms such as mosaic patterns, yellowing and deformities on leaves, while fruits develop brown wrinkled spots, deformations and uneven ripening, reducing their yield and marketability.
South Australian chief plant health officer Nick Secomb encouraged growers to reduce the risk of spreading pests and diseases by cleaning shoes, hands, and equipment regularly, and to report signs of the disease.
The Northern Adelaide Plains are home to some of the most productive vegetable farms in the nation with large greenhouses and open farm operations producing tomatoes, cauliflowers, sweet potatoes, cucumbers, eggplants, mushrooms and many more products.
The virus has been reported in Canada, China, Germany, Greece, Israel, Italy, Jordan, Mexico, UK, USA, and Northern Palestine.
