White butterfly (Pieris rapae) and the white rust Albugo candida on Cook’s scurvy grass (Lepidium oleraceum)
Once widespread, Cook’s scurvy grass (or nau, Lepidium oleraceum) is now confined to a few offshore populations. Classed as nationally endangered by the New Zealand Department of Conservation, populations of Cook’s scurvy grass are threatened by a number of factors, including introduced herbivorous insect species such as the white butterfly (Pieris rapae) and white rust infection caused by the oomycete Albugo candida.