Principle insect and disease problems are the cabbage looper and imported cabbage worm, cabbage root maggot, aphids, flea beetles, blackleg, black rot, clubroot, and yellows.
Symptom Probable Cause
Seedlings cut off at base - Cutworm
Leaves riddled with shot-holes; plant weakens - Flea Beetles
Leaves wrinkled or curled; discolored, stunted, tend to fall off - Aphids
Holes in leaves - Caterpillars
Discolored heads - Head Exposed Too Much Light
Gray patches on lower leaves spread upward - Downy Mildew, Fungal Disease
White butterflies; ragged holes in leaves, bit of green excrement on leaves - Cabbage Worms
Holes in leaves - Cabbage Loopers
Small holes, transparent holes in leaves - Caterpillar Of Diamondback Moths
Plants disappear all or in part- Deer
Plants disappear all or in part - Rabbits
Plants disappear all or in part- Woodchucks
Young plants wilt in heat, may yellow and die.- Cabbage Maggots
Foliage eaten - Vegetable Weevil