Bt is a species of bacterium that likes to eat caterpillar insides, as well as some other insects, killing them after a few days.

Best' is relative and needs scale. But currently Bt is an effective way to combat them, provided you know what you are doing and follow all directions carefully and faithfully.

Dan

Rachel - BT is my cole crop gardening friend! It is a microbial insecticide that attacks the inner lining of a leaf chewing worm's stomach. When it has ingested enough of it, it gets a real bad tummy ache, and starves itself to death. Cool!!!

EG

BT stands for bacillus thuringiensis . In past gardening lives I seem to remember it turning tomato horn worms black.
I think it's the next best thing to hand picking. But as Dan says you need to follow the directions carefully.