Cabbage White

Pieris rapae — the small white, called the cabbage white in North America — is the most agriculturally consequential butterfly in the world. Native to Europe and temperate Asia, the species was accidentally introduced to Quebec, Canada in 1860 and to the United States via New York around 1868. It spread across the entire North American continent within 20 years and now occurs in every US state and every Canadian province where Brassica vegetables are grown. P. rapae is also established across South America, Australia, New Zealand, and most of Eurasia outside its native range. The caterpillars are bright green with a faint yellow stripe and feed on the leaves of plants in family Brassicaceae: cabbage, broccoli, cauliflower, kale, brussels sprouts, kohlrabi, bok choy, mustards, and ornamental brassicas. Damage is severe — a single caterpillar can consume its body weight in cabbage tissue per day, and infestations of 10-30 caterpillars per plant routinely defoliate entire vegetable crops. USDA estimates US economic damage exceeds $200 million per year. The adult butterfly is unmistakable: white wings with one (males) or two (females) small black dots, wingspan ~5 cm. Adults live 2-3 weeks and produce 3-7 generations per year depending on latitude. The species is a major focus of integrated pest management research and has driven the development of organic Bt (Bacillus thuringiensis) sprays and trap-cropping techniques.