As few as were on the leaves, I just smashed them. I have used Sevin dust before when there were a lot of them in the garden. Just a light dusting on the leaves before the heads appear.
That's what I do with tobacco horn-worms. Since I don't have acres of tobacco, I go out 3 times a day and examine the plants and smash the little buggers.
I actually get fairly loud doing it, taking joy in their destruction. ;)
/johnny