I find it strange that articles about farmers not being able to get workers to pick their crops come out whenever there is a controversy concerning illegal immigration and deportation.
From my own experience, I know that most foreign workers on the farms have seasonal agriculture work visas. However, even when all the visas are taken up to fill the positions open at the various farms, many do not show up. It can be due to their working at manufacturing and light industrial plants, Home Depot, Lowes, warehouses, or even construction jobs where they pay much more than what would be received from work in the fields.
There is also the union factor which reporters fail to bring into the stories as well. They wish to use the readers' ignorance on the matter of where the non-documented workers go for jobs, and the last place is on the farms.
There used to be college students during their break in semester studies who would go out to seek work in the fields. However, unions persuaded them not to, as they were weakening their power over the farm owners.
You can check the data on the number of visas being taken out and filled for work compared to the numbers of workers who actually show up to work on the farms, which they used to get into the country.
When I hear crops are not being picked, I immediately think unions. Many workers who come across the border don't want to mess with the unions or pay dues, monetary or otherwise.
You really should talk to some of these "seasonal workers" that go to the higher-paying jobs. I have seen them with signs that say, "Will not work for less than $20 per hour."