Thistle Tortoise Beetle Larva

Cassida rubiginosa was brought to New Zealand for use as a biological control agent against Canada thistle in 2006. In New Zealand this species is commonly referred to as the 'green thistle beetle' by landowners and biological control practitioners. Field releases of egg-laying adults were first carried out in Otago and Southland in spring 2007. Beetle populations at early release sites in Southland have become established and are already having a minor localized impact on the thistles. It is estimated that Canada thistle (known commonly in New Zealand as 'Californian thistle') costs landowners around $32 million per year in Otago and Southland alone.