This is how they start, munching on the juicy green foliage of the host plant. In this case they are on my second year hollyhocks. On any one leaf I counted 10-15 larvae at any time.
They work their way through the plants leaves to get enough energy to sustain their transformation into cabbage moths.
Leaving behind leaves on your favorite ornamentals and vegetables that look like this:
Not a pretty sight is it? This hollyhock wasn't intended to be a lace leaf variety. When I finally caught the cabbage worms I applied an insecticidal soap that contains neem oil which works as a feeding deterrent and as a growth regulator. Quite frankly I just want them dead and gone. (These worms also targeted a rose bush we have in the front garden. They have not made me very happy.) I did use a very effective if somewhat time consuming method when I first saw them, I call it thumbicide. Just take the little worms between your thumb and forefinger (I used gloves) and squeeze tightly. (If you're angry enough this may help you channel that anger!) If that is a little too icky for you consider using Bacillus thuringiensis or BT for short. It's a bacteria that is harmless to people but not to insect larvae. Another option is simple prevention. If you have a large crop of cabbage invest in row covers to prevent the moths from laying their eggs in the first place! I checked my one cabbage plant that came up from seed and found a small infestation there as well, you can bet I'll be definding my cabbage. I've got a batch of coleslaw that is depending on my fortitude!
Insects are just one of the many challenges in gardening, frustrating yes, but figuring out how to deal with them will make you a better gardener!
For more information on their control and lifecycle go to the University of Florida's Cabbage Looper Information Page.
To help fend off cabbage loopers from vegetable crops try this from Gardener's Supply:
|Pop-Up Pest Control Nets|