Well, since it's a leaf eating caterpillar, I'd go with what TC and Chris S. suggested...any product containing Bacillus Thurgensis (BT) like the ones mentioned, Dipel Dust or Thuricide. And if you can, hand pick them off at night as well to help out...
Slugs I've been able to handle with the old beer in a jar trick.
Yep it's a caterpillar.
Dipel Dust and/or hand picking and feeding to the fish.
Thanks everyone. I've been doing the flashlight kill method. Haven't caught that many and yet the Kale looks much better (I guess it was only a few of them doing all that damage).
I do a quick check with flashlight every other night or so and kill ratio dirt garden to aquaponics is about 5 to 1, respectively. The gravel beds don't seem to support nearly the same number of pests. One worm returning to the same plant each night can do a lot of damage and as you've noticed things turn around quickly once you kill that worm. Certain conditions favor the bug hunting - some nights they're out feeding and others not. I drop the aquaponics bugs in the fish tank and whether the fish eat them or not they become part of the system.
I don't know what is causing the problem, but if you want to test for cutworms hiding in your substrate, just flood a bed above the substrate and see what comes swimming up looking for air. I found about 50 cutworms in my system when I tried it.
Cool Nathan. The simple solution is sometimes the best one. Good fish food too.