Some of Australia's visa's require that the applicant spend a few months working on a farm, usually fruit-picking. These workers are still entitled to the same minimum wages (as far as I know) and other protections, in theory.

(Australia's geographical isolation makes it difficult to attract seasonal workers, unlike throughout Europe where traveling for work is comparatively cheaper and easier.)

However, farmers have always benefited from the fact that people wanted the visa more than the didn't want to work — many workers are taken advantage of. Now that there are none of these workers, farmers are having to complete for labor like anyone else and that is costing more than they intended.