It looks like a cabbage worm. I don't know what those little things on its back are, though.

-Anne

Nadata gibbosa, larva
http://www.discoverlife.org/mp/20q?guide=Caterpillars

Feeds on: Principally oak and other Fagaceae, but also reported from alder, birch, cherry, chestnut, maple, plum, rose and willow.

Which becomes the:

White-dotted Prominent Moth
http://bugguide.net/node/view/425

Don't know what the smaller things are.

Here is a link that might be useful: Nadata gibbosa ��

Do they eat cruciferous vegetables?

Gregory: Cabbage looper, cabbage worm, etc. Not sure about the parasites, though. Try posting in the garden Clinic forum.

They are PROBABLY the culprit. Or it could be a combination of pests. In either case, caterpillars eat foliage and traditional soaps and oils will not control them. However, I'd start treatments of BT(very safe and available at any garden center) and picking off by hand and you'll see improvement in the foliage.

Got to stay diligent with the treatments though -- after the initial once every week for 2 weeks, go to ONCE every TWO weeks.

Kevin

This post was edited by woohooman on Sat, Nov 2, 13 at 22:11

Yes, a cabbage looper. There are species of parasitic wasps specialize in those caterpillars and that's probably what's going on. Natural and beneficial control for the pests.

Those might be Tachinid fly larvae as well, they are also parasitoids.