Jacobaea vulgaris Gaertn.- Ragwort

Ragwort, Facobaea vulgaris, is a weed of major economic significance in Vic and Tas due to its detrimental effects on agricultural production and toxicity to livestock. Annual production losses have been conservatively estimated at well over $4 million per year. Biological control programs have resulted in the release of seven agents since 1930. Although five agents have established, the cinnabar moth Tyria jacobaeae is confined to only one site in Vic, where its impact on ragwort is not significant, and it has failed to establish in Tas. Two species of flea-beetle, Longitarsus flavicornis and Longitarsus jacobaeae, have established in both Vic and Tas. In Tas, the root-feeding L. flavicornis has become the dominant flea-beetle and is now widespread on ragwort throughout the state. It has had a major impact and is capable of reducing infestations by up to 95% at some sites, resulting in multi-million dollar savings to the dairy and beef industries through increases in production. Biological control now ranges from substantial to complete in many parts of Tas. However, on some properties unfavourable site conditions and incompatible management strategies have restricted its impact. In Vic, L. flavicornis has established only in high-rainfall locations above 500 m and has spread slowly. It has not had a significant impact, nor has the less common L. jacobaeae. Two other agents, the ragwort stem- and crown-boring moth Cochylis atricapitana and the ragwort plume moth Platyptilia isodactyla are now well established in Vic and Tas and are continuing to spread naturally. Both species have been observed causing considerable damage to crowns and stems at field sites in these states, with trials in Vic indicating that they are capable of significantly reducing plant vigour and reproductive output. In Tas, these species are also expected to provide significant control, particularly in areas where L. flavicornis impact is restricted. Studies in Tas have provided comprehensive information on the biology and behaviour of L. flavicornis under field conditions, and its use and effectiveness in integrated management programs including herbicide control. Field studies incorporating C. atricapitana and P. isodactyla are now required if a more effective integrated control system for ragwort, using a combination of these biological control agents, is to be achieved.