Two biological control options for Sonchus oleraceus in Australia.
Common sowthistle, Sonchus oleraceus (Asteraceae), is a widespread invader of disturbed ecosystems in Australia. It is a major weed of Australian cropping systems, its incidence having increased over the past two decades. Surveys of this weed throughout Australia have found two organisms on Sonchus spp. that are very damaging; an undescribed species of eriophyid mite (Aceria sp.) causing extensive leaf-rolling damage and a rust fungus, Miyagia pseudosphaeria. Both appear to be specific to Sonchus spp. and could be considered for a conservative approach to biological control. The interactions of these two organisms with the weed species and the only native sowthistle species in Australia, Sonchus hydrophilus, are being investigated to establish the origins of these organisms and likely impact, both in natural and cropping ecosystems.