Imported cabbageworms are an insidious garden pest.
Cabbageworms start out as tiny yellow or white, rocket-shaped eggs that are laid singly on the undersides of leaves. Then, slightly fuzzy green caterpillars emerge and start feeding, and feed they do!
According to the UC IMP (Integrated Pest Management) page: biological controls include natural enemies such as the pupal parasite Pteromalus puparum; the larval parasites Apanteles glomeratus, Microplitis plutella, and several tachinid flies; and egg parasites in the Trichogramma genus. Biological control and sprays of Bacillus thuringiensis (Bt) and the Entrust formulation of spinosad are organically acceptable management tools.
In addition to regularly monitoring plants for the presence of cabbageworms, I have trained my dog to chase cabbage butterflies out of my yard.
You can grow a surprising amount of food in your own yard. Ask me how!