Biological control of ragwort ( Senecio jacobaea L.) in Australia

Abstract

The history of biological control of ragwort in Australia is outlined. Five biological control species have been released in southern Australia since the 1930s but only 3 have established. The flea beetle, Longitarsus flavicornis, has now dispersed over all ragwort infested areas of southern Tasmania and 90 % of infestations in northern Tasmania. In some localities it has reduced ragwort densities by up to 95%. L. flavicornis has only established in high altitude, high rainfall locations in Victoria from where it has spread very slowly and has not had a significant impact. Longitarsus jacobaeae has established in a few isolated locations in Tasmania and Victoria and is yet to have a significant impact. The ragwort stem and crown boring moth, Cochylis atricapitana, is establishing in both Victoria and Tasmania with recoveries at 35 % and 67 % of release sites respectively. At one Victorian site it has dispersed more than 10 sq. km and is reducing the height of flow-ering ragwort plants and killing smaller rosettes during autumn. Numerous attempts between 1930 and 1983 to establish Northern Hemisphere biotypes of the cinnabar moth, Tyria jacobaeae, have failed. Since 1995, attempts have been made to establish a New Zealand biotype that is adapted to Southern Hemisphere conditions. Although recoveries have been made from several sites there is still no evidence that it can be permanently established in Australia. The ragwort plume moth, Platyptilia isodactyla, is currently undergoing host specificity testing and, if specific, will be released during spring/summer