I think it depends how the incoming workers are being accommodated and fed. If they are staying on site, or all together, and if they are being provided with food and other necessities so that they don't have to leave the fruit farms, then flying them in for a couple of months is no harm.
It's like the outback farms in Australia. They fly groups in who stay on site and work for a couple of months, then head back to the cities. Awful conditions but (relatively) good pay makes it bearable for young people.
If students were busing in from all over the country and going home at night it would be much worse from an infection point of view.
Keelings should clarify where they are all staying, though.