"South Australia is the only mainland state in Australia that is fruit fly free," Mr McEwen said.

"We are very proud of that and work hard to keep it that way."

In the past 12 months, State Government inspectors deployed at random roadblocks have seized 1262 kilograms of fruit and fruiting vegetables.

"Any fruit and vegetables you carry into SA could be the deadly catalyst that brings our multi-million dollar horticulture industry to its knees," Mr McEwen said.

"All it takes is just one piece of infested fruit being brought into South Australia– whether that’s by car, plane, train, truck and caravan.

"If you are travelling back into South Australia, make sure you leave any fruit and vegetables in disposal bins or at permanent quarantine roadblocks."

Penalties for bringing fruit and vegetables into SA range from $55 to $210 (plus a $20 levy) depending on the quantity of produce.

No penalties are imposed if produce is voluntarily deposited at permanent quarantine roadblocks.

Travellers returning to the Riverland with fruit and vegetables purchased from a shop must carry a receipt of purchase or a Plant Health Certificate.

Home-grown fruit and vegetables are not to be taken into the Riverland.

Fruit disposal bins are located at the airport, highway entry points, and bus and interstate train stations.

Mobile random roadblocks will also be in operation over the long weekend.

* If people have inadvertently brought fruit into SA, please contact the Fruit Fly Hotline on 1300 666 010 for disposal.