Earlier quoted context omitted.
At 20 USD/hour I think you would be able to fill these jobs. But if you want to make that salary picking fruit, then we'll have to pay more for it -- or you'll need to have some automation to increase productivity. I doubt we'll want to pay more, consumers would rather buy imports instead.
Everything I have ever read indicates that white Americans don't want farm labor jobs even if you pay $20/hour.
$20/hour for temporary backbreaking work in exchange for not being near friends or family, having to move constantly, having to live in a rural area (not what most people want), having no upward income mobility.
The people that do it, do it because they have no better option. Not because they want to.