These nasties are the culprits, what are they and how to get rid of them?
What kind of caterpillar is eating my cauliflower (pics)
Looks like an army worm. Bt (Dipel or Thuricide) should work.
Would this be safe if I have been growing organically? http://www.gardensafe.com/Products-and-Solutions/Insecticide/Bt-Worm-and-Caterpillar-Killer.aspx
Bt is on the safe list.
And, they aren't called "army' worms for no reason...where there's one, there are usually scores, so get on it in a hurry.
They can tear you up overnight...the faster you put some Bt in their guts, the better off your garden will be!
The Bt needs to be sprayed on the LEAVES, top and bottom.
It works when the worms eat the leaves and the agent enters their digestive tract, so spray when there's little chance of immediate rain, so the Bt isn't washed off right away...
Army worms is the right answer. Get after them quich or they will defoliate your plants. Squashing them might work, but the way they hit us down here is just be time consuming.