All sources said that the cabbage looper is "very destructive" to plants due to its "voracious consumption" of leaves. Watch out plants!
Solutions: One suggestion is to attract beneficial insects by planting flowers, such as marigolds, calendula, sunflower, daisy, alyssum or dill nearby. These plants attract insects that attack and kill cabbage loopers and cabbage butterflies.
http://www.bhg.com/gardening/pests/insects-diseases-weeds/stop-cabbage-loopers/
Another solution is to cover the plant with netting to keep the insects out.
Photos above by J. Zacarias





















