Many farms are run purely by the family, and involve no work from outside forces. It seems ridiculous that barring illegal workers from being on the farm would eliminate the vitality of every farm in America, but it may require new groups of people to take on more responsiblity for doing this labor.
Without illegal labor farms would still exist today, but there would be a lot less of them. Illegal labor allows smaller farms to stay afloat while large farms with high dollar contracts can afford to pay their laborers, whether they do this or not. There are many ways for farms to be profitable without illegal labor.
Yes, farms are not solely based on the labor of immigrants. Many farms are still run in the same way that they have always been run; family. Over two generations of families are still known to live on a slice of land and all contribute to the future of the farm by labor. I do think that the output of farms would be greatly impacted by the lack of illegal labor.
Farms would still exist in America without illegal labor. It's just that products would cost more money. Local farmers would be more prominent because those entities could compete with mega-farms that use illegal immigrant workers. Farms would still exist in today's world, but more and more farmers would be family operations that serve local populations.
Yes, farms would still exist without illegal labor. While many farmers do take advantage of inexpensive, illegal labor to increase their profit margin, there is no question that farming could certainly survive without it, provided all farms were operating under the same guidelines. Perhaps with some government organization, and assistance, with the movement towards using strictly workers who are in this country legally, the structure of the farming system would adjust and adapt to the increased labor costs.