Use a Bacillus thuriengensis insecticide. Trichogramma wasps exist naturally and can be introduced to attack eggs. DBM have black heads, cabbage loopers have black heads and spots on the body, and white imported cabbage worms have brown heads and are light-green and hairy. Scouting for larvae before and after insecticide application with records will give control level obtained and indicate whether additional sprays are needed. Cabbage worms are velvety green, hairy, and slow moving.
Cabbage loopers are light-green, smooth, and loop when they move.
Diamondback moth larvae are very light green, pointed at both ends, and wiggle when disturbed. They also spin a silken thread. Larva of the diamondback moth. In small gardens, barriers around plants can prevent serious cutworm damage. By encircling individual plants with cardboard or metal collars pressed into the soil, cutworms are barricaded from the plants.