Eradication of the exotic weeds Helenium amarum (Rafin) H.L. and Eupatorium serotinum Michx. from south-eastern Queensland.
Successful eradication of two potentially serious exotic weeds, H. amarum (bitterweed) and E. serotinum (seroty weed), from separate sites in southeastern Queensland, Australia is documented. Bitterweed was first detected in 1953. It ultimately spread over 50 ha, with a single satellite infestation establishing at 1.6 km from the original infestation, and required 370 person-days over a period of 39 years to eradicate. Seroty weed was discovered in 1962. It spread over a comparatively smaller area (0.5 ha), with one satellite infestation establishing at 1.0 km from the original infestation, and took 50 person-days over an 18 year period to eradicate. While both species are wind-dispersed, the relative positions of satellites suggest that other vectors, e.g. transported soil or vehicular movement, may have been more effective. Both plants were readily controlled by foliar application of 2,4-D herbicides. However, perusal of reports detailing surveillance and control missions suggests that seed dispersal and extended seed longevity prolonged both eradication efforts.