Biological control of horehound: lessons from South Australia

C.R. Clarke, J. Baker, M.A. Keller and R.T. Roush, CRC for Weed Management Systems and Department of Applied and Molecular Ecology, The University of Adelaide, Waite Road, Urrbrae, South Australia 5064, Australia.


The biological control program against horehound in South Australia has focused on evaluation of the horehound plume moth, Wheeleria spilodactylus (Curtis), and initial releases of the horehound clearwing moth, Chamaesphecia mysiniformis Rambur. The plume moth has established at 37 of the 51 release sites studied in South Australia. The current rate of population increase in the plume moth, greater than 100 fold annually, appears to be enough to cover South Australia with horehound-suppressing densities of larvae in less than five years. However, the spread of populations away from release sites indicates that it will take 27 500 years for the plume moth to become distributed across the whole of South Australia. This could be overcome by actively redistributing the moth to many more sites. The horehound clearwing moth was released at three sites in 1999. The status of this insect will not be known until the end of this year. Evaluation of the impact of these biological control agents is desirable to determine their impact, to justify future redistribution efforts and to determine if additional natural enemies should be imported to enhance biological control.


Plant Protection Quarterly (2000) 15 (1) 29-32.