Nobody forced the farmers to become reliant on migrant workers though. It was just a simple decision for them: cheap labor that's available today or expensive labor... They mostly went with cheap, and now they don't have anyone available. Tough luck I guess, but it always was just a question of time until this happened.
Not strictly true in a competative market that races for the lowest possible cost. It's the toxic company culture mentality that in this case, the shareholders are the customers and they want to have their cheap food.
Hence many farmers been squeezed via large corporations and dairy farmers and many others operate upon margins that are just insane and unsustainable that many end up producing at a loss overall.