He'd go out in the vineyards & hand-apply predatory mites onto the vines with a paintbrush.
"There you go!" he said. "I applied predatory mites. Your vineyard's protected. Just don't spray anything that would kill them."
So here's the thing about that,
You only need to put predatory mites onto your plants if you're in a greenhouse. And you need to put out thousands. A few per plant with a paintbrush won't do it.
But for crops in an open field, predatory mites usually show up on their own. No application necessary.