For a self-professed libertarian, economics do not seem to be your forte.
Moses did not walk down Mount Sinai with a stone tablet declaring "Yea, verily, strawberry pickers shall make $5/hour forever." The market determines their wages.
If the US expelled every single illegal immigrant and reduced immigration by unskilled labor (which would seem to be the market your post addresses), the supply of unskilled agricultural labor would drop. Strawberry growers facing their crop rotting in the field would raise wages of strawberry pickers to the point where they could get at least some people in the US to pick their crop to get it to market. The price of strawberries in supermarkets would rise probably to the point that many consumers who buy strawberries at today's prices would forego consumption of strawberries at the new (post-immigration) equilibrium price. You are correct about this point: Some growers would decline harvesting the crop due to increased labor costs. Do you think they would plant the same acreage in strawberries the next season? They would cut their losses in the short term and promise themselves that they would never put themselves in that bind again, but would find something else to do (either grow something else or leave agriculture altogether).
Over the next few seasons, some producers would shift to producing other commodities not so labor-intensive, some mechanical genius would design a machine that would pick some strawberries at an acceptable rate (probably crushing some ripe strawberries and picking some that were not yet ripe when picked, but would get the job done cheaper than the new equilibrium wage), some American labor would be attracted to the fields at the new wage rates, or some combination of all of the above.
But here's the point, while it might suck for strawberry consumers (some would pay the new higher prices, some would forego consumption), it would be a boon for unskilled/semi-skilled American laborers.
