Green Caterpillars

[El Sapo]

This year I planted my first ever garden and it has gone remarkably well up until now. Upon returning from a mini-vacation today I find that my collard green, brussel sprout and cabbage plants are under assault. They look like someone took a shotgun to them and the culprits are some very well camouflaged green caterpillars that I began finding on the plants.

I squashed at least 20 of them today but I'm concerned they'll come back. I had been planning on doing more of an organic approach with the garden but I'm willing to break out some serious firepower against these suckers if need be.

What are these caterpillars and what is the best way to get rid of them?

 

[Sangre Naranjada]

Start here

That will give you a good jump on ID as well as control measures.

 

[El Sapo]

Thank you for the link, this was exactly what I needed. They are Cabbage Loopers

My garden is small enough that I can control them by hand. Now I just need to decide which is a worse fate for them (the soapy water suggested or death by squashing) and then go that route.