Farmers say they can't get legal workers to work for the wages they pay and the seasons are short. I see two answers to this. First, pay higher wages. This will drive prices up, but that is the price we will pay to stop the illegal immigration. This would have to be coupled with making all employers use E-Verify and penalize those that don't.
Second, require all those that are receiving unemployment and welfare to work at these seasonal jobs as a condition of receiving their money from the government. This in turn would help bring down the national debt and make labor available for the farmers.