This, btw, happens all across the EU is my impression. Modern-day slavery very much alive globally even!
If farmers paid good wages they wouldn't need to rely on foreign labour and food prices would go up. This is a workable solution, but is is what people living in western countries want?
We have the same issue here in the UK with the NHS.. We pay NHS workers terrible wages so we need to import foreign labour because wages aren't high enough to attract domestic workers. In one sense it's great because we get better health care than we would otherwise afford and foreigners have an opportunity to get better pay in the UK (even if it's bad by UK standards).
I've found many people here get angry about what we pay NHS workers while also getting angry about NHS waiting times. If we wanted to we could increase wages which would either require resource cuts and lower output or higher taxes for the same level of care. It would also mean we wouldn't need to depend on foreign labour, but who benefits from this? By paying more foreigners now have less opportunity to move to the UK and British citizens have sub-par / higher cost health care.
Presumably, it's the same with agricultural workers. Sure you can pay more, but who benefits from it? The root "problem" is that labour is extremely cheap outside of developed countries. Developed countries can cut themselves off from that labour supply if they like, but I have no idea what the economic incentive (or benefit) of doing so is for either the workers or the citizens. Call it modern-day slavery if you like but these are consensual working relationships, which presumably wouldn't take place if they didn't benefit both the worker and the employer.
So long as labour remains cheap outside of the developed world a trade off will always exist – paying more will just mean higher prices for citizens and fewer opportunities for those living in the poorest parts of the world, but on the up side you can say you pay a fairer wage by your own national standards.
It would end supply of people who are willing to work for unlivable wages, thus making wages for low-end work to go up. The lowest rungs of society would benefit greatly from it, while everyone pay would pay for it (via increased prices).
The UK has done, it is known as Brexit.
Jobseeker agencies paid by the Federal government to 'place' workers, this doesn't factor in the jobs actually being suitable or useful mind.
The workers on unemployment are also required to apply for a quota of jobs or risk losing their benefits, even though there may actually be no new jobs to apply for.
I'll pay you minimum wage, but charge you exorbitant amounts for board and lodging and you have no choice because it's the middle of nowhere.
Or for the extra dodgy types, cash payments below minimum wage because they know international workers are less likely to know their rights and be aware of what the minimum wage is.