It isn't a government problem. It is a farmers doing things as cheaply as possible problem.
Why aren't you asking what the farmers are going to do when they can no longer import unskilled EU migrants? If you don't know by now then the answer is that they'll have to employ those people that currently won't do it for the pittance minus accommodation costs that they currently offer and will have to increase their compensation package.
From the link I posted above is the pay page. They are offering
50p per hour above minimum wage but then there's over £200 per month of accommodation costs to come off that for the luxury of a shared shipping container with 5 strangers.
https://www.broadwaterfarm.biz/summer-fruit-picking-uk/
They will be selling food and everything else these people need at inflated prices from the onsite shop as well. It is obvious why they prefer importing labour and it is disgusting that we allow it to happen just to get cheaper fruit and veg and to line the pockets of farmers and supermarkets.
* Edited because I was looking at last year's minimum wage figures.