This product active ingredient is "spinosad". How it works is when bugs bite the leaves which you have sprayed, it kills them. So "generally" it won't kill beneficial bugs - unless you spray something and within 3 hours a beneficial bug (such as a bee) visits the plant before it dries.

Anyway - so "directly" it won't kill the cabbage butterflies, as they don't munch on the leaves - their larva do (the little green worms). The larva will be killed by the spinosad very quickly - at the very least over night. And eventually, the butterfly population will start to disappear, as you are killing all of the larva.

Hope that helps explain things a bit.

I use Bt Worm killer on my plants to control hornworms, cabbage loopers, and other wormy type critters. (I think it's made by Green Light) One application pretty much eradicated them from the garden. I also use beneficial nematodes in the garden and parasitic wasps, all organic controls.

Here is a link that might be useful: The Haphazard Gardener

Cap. J.s' dead bug concentrate KILLS STINK BUGS!!!! The required mix is 4oz of the concentrate to 1gal water. Show no mercy! It takes about 5 or so minutes, but they do die.

I dusted my cucumbers, cabbage,broccoli,ect. with captain jack's dead bug brew. Two hours later it started to rain and washed all the dust off. Should I wait for the minimum days to reapply. What should I do? The beetles were eating my cucumber plants.

Does it work on tomato horn worms

Does not work on Mexican Bean Beetles, the larvae of which are horrendous pests which destroy squash more than beans. Superbugs apparently.

...Bagworms on evergreens is my problem. Anybody have experience with Captain Jack's Brew on bagworms??