It sounds like you might have an infestation of imported cabbageworms, although other worms may also attack cabbage, such as cabbage loopers. Imported cabbageworm is a green caterpillar with a faint yellow stripe down its back (see the top photo above); eggs are yellow, laid under leaves; you can often see the poop left on the leaves. Cabbage loopers are green with 2 white or yellow lines down their back, and move sort of like an inchworm; eggs are light green; you may notice cocoons in leaves. For caterpillar control, you might try some of the methods suggested in the above article. If you have a small garden, handpicking is the most effective. For heavy infestations, however, you might try spraying BTK (Bacillus thuringiensis var. kurstaki) according to manufacturer’s directions. Row covers help prevent the adult white butterfly from laying eggs on the leaves, but of course it won’t help control the pests already there. Remove weeds around the garden, especially from the mustard family. Good luck!
It sounds like you might have an infestation of imported cabbageworms, although other worms may also attack cabbage, such as cabbage loopers. Imported cabbageworm is a green caterpillar with a faint yellow stripe down its back (see the top photo above); eggs are yellow, laid under leaves; you can often see the poop left on the leaves. Cabbage loopers are green with 2 white or yellow lines down their back, and move sort of like an inchworm; eggs are light green; you may notice cocoons in leaves. For caterpillar control, you might try some of the methods suggested in the above article. If you have a small garden, handpicking is the most effective. For heavy infestations, however, you might try spraying BTK (Bacillus thuringiensis var. kurstaki) according to manufacturer’s directions. Row covers help prevent the adult white butterfly from laying eggs on the leaves, but of course it won’t help control the pests already there. Remove weeds around the garden, especially from the mustard family. Good luck!