The white butterfly is the cabbage worm. There are three species, but the imported version is the most destructive. Small green caterpillars that blend into the foliage.
https://entnemdept.ufl.edu/cre...
Loopers are the larvae of a brown moth. The larvae are what we old folks called inch worms or measuring worms.. They anchor their rear reach and grab a hold, then pull their rear up
https://entnemdept.ufl.edu/cre...
Common Bt either in liquid or dust form is quite effective and about as harmless to other organisms as is possible. Unless you are mixing large amounts and have more than a couple of gallons left over, I would just pour it in the garden. Once it gets wet it biodegrades rapidly which is why it is useless when stored for a day or more.
