Biology

• The white butterfly is common throughout the country and is a common pest of brassicas
• Adult butterflies have creamy white wings with the tips of the forewings tipped with grey or black
• Females have two black spots on each forewing while males have only one. Both have a single black spot on each hind wing
• The average wingspan is about 50 mm
• Butterflies are commonly seen flying above brassica crops or feeding on the nectar of flowers
• The females lay yellow oval eggs singularly on the underside of brassica leaves
• Each female can produce up to 400 eggs. In warm weather these hatch in 8-10 days giving rise to 1.5 mm long yellow/green caterpillars. As these grow they become a dull green colour with an orange strip down their backs
• There are five caterpillar stages and eventually they reach about 25 mm long. They pupate off the host plant on fence posts, nearby shrubs or buildings
• It takes 20-40 days from egg to pupa and a further 15-18 days to emerge as a new adult
• Depending on temperature there can be three or four generations a year
• They spend the winter as pupae with butterflies appearing again in spring.