Caterpillars do not like sage. There are bacterial pesticides, like Bacillus thuringiensis. Everyone wants butterflies, but nobody wants caterpillars... Only 1 to 5 percent reaches that stage. (The caterpillar is a larva of the butterfly. Chickens lusts them).

rupsenYou can catch caterpillars. But there are always a lot more than you think! While you're busy butterflies fluttering all around the cabbage again with a new load. And caterpillars are growing fast!
I have at the cabbage plants a pot (with lid) and tweezers. Fish and chicken are fond of caterpillars. In trees and bushes you can hang a rag, a wad of cardboard or some branches. The caterpillars come together here to pupate and so you can remove them.

Caterpillars are often difficult to see, especially if they are small. They have more often camouflage- than striking quenching colors. Sometimes you see them barely even when they sit in front of you. In the same green as the cabbage leaf. But of course you can see that the leaves are eaten.
Or you see droppings (spheres) located in the leaf axils. If they are fresh green, the track is not far. If there is one, there are more. Search on and under every leaf. And look especially well in the soft, protective heart of the cabbage. Several times a day. If you open the petals sometimes you can find on every leaf, as in Russian dolls, each time a new resident.
Hold a sheet under the track because they let themselves fall if you touch them. Good chance that you will no longer find them.
If after a few hours you try once again, you can definitely find other copies.
If you have a few big caterpillars found that mainly means that you have not already seen the little ones days ago. Look at the under side of large bracts. You recognize the grouped eggs and can easily press and rub them. Before the worms gnaw. Same with small worms, which are all still easily very close to each other. Hit in times then you have less work and less damage.

(As I noted in August that my climbing roses suddenly had much less leaves I've there harvested also huge primarily black and orange dotted green caterpillars and thrown into my pond. Three days later I fished seven dead fish.)

The best protection and prevention is a cover with fine gauze, without openings, to make sure that butterflies can’t reach the plants.

"In a better -ordered world the caterpillars would show up in October and devour the leaves as they lie on the ground.” (Edward Stevenson)