I just read in an old OG magazine about a corn farmer who uses trichogramma wasps -- he buys cards of wasp eggs and uses twice the card than recommended. He uses pheromone traps to monitor for the pest moths and as soon as adults start showing up in the trap, he sets out the wasp eggs because trichogramma wasps attack the EGGS before the caterpillars hatch. Should work for these as well. Definitely plant to attract beneficials. Check out the sticky in Permaculture forum.
Edited to add: The trouble with this kind of solution is that the "beneficials" also attack desirable butterfly and moth eggs and larvae. Each year, I have to bring most of the Monarch butterfly eggs and cats inside to raise because if I leave them outside, they get parasitized and don't grow up to be butterflies. (Nothing more heart-breaking than to watch the 5th instar cat struggling to molt and crysalize, only to end up with the "alien" effect and find the empty cat husk in the morning. I also find them outside in late summer
) Right now, I'm debating on what to do with [img]https://i290.photobucket.com/albums/ll272/applesbucket/Image1455.jpg[/img]
He ate the leading branch including a couple of green Grape tomatoes, but my kids are thrilled to see him getting bigger and bigger. I just might have to put him in with the cabbage worm my 9 yr old is raising