Apparently listening to Jeremy Vine, there is no real shortage of fruit pickers. Farmers are rejecting British applicants in order to get cheaper foreign workers from Romania and thus force the government to continue with freedom of movement for fruit pickers. One caller claimed to have made over 30 applications, all rejected.

There were complaints that the job conditions were deliberately set so bad that it forced british workers out of contention. You had to live in a caravan with strangers, you couldn't drive to work. This would be very difficult for people with families.
There were also allegations that farmers were cynically rejecting british workers in order to let all the fruit rot as a demonstration to the government that we need foreign workers to freely come over.

All sounds very familiar.

If farmers do employ British people, they make it hard for them, then they eventually end up quitting.

Even though there's no skill in fruit picking, farmer's don't want to pay minimum wage. Farmers advertise with DWP just to make them look good but the farmers would never interview them for a job unless they very desperate.

Most farmers these days are no more than landowners who can't wait to sell up to the highest bidder.