"Some of these proposals would create additional opportunities for persons from other countries to work legally in U.S. agriculture, while others would use different methods to enforce existing U.S. immigration restrictions. Any of these proposals, if enacted, are likely to have a substantial impact on U.S. agriculture and the market for hired farm labor. Labor is a major input for many agricultural sectors, and persons not authorized to work legally in the United States constitute a large share of the farmworkers employed by U.S. agriculture."
They note that labor accounts for about 17 percent of agriculture's variable production expenses and roughly 40 percent for fruit and vegetable farms and nurseries." The chart below is helpful in understanding how that is substantial for some crops.