The cabbage white caterpillar is a pest that feeds off members of the 
cabbage family (including cabbage, broccoli and brussel sprouts),
nasturtiums and wild crucifers. The damage to the cabbage family is most
significant because these plants are grown as food crops. The level of the
caterpillar is controlled chemically by using insecticides or biologically by 
an ichneumon fly which lays its eggs in the caterpillar. When the eggs hatch
the ichneumon larvae eat the caterpillar therefore killing it.