Biological control of St. John's wort: past, present and future
D.T. Briese, CSIRO Entomology and Co-operative Research Centre for Weed Management Systems, GPO Box 1700, Canberra, ACT 2601, Australia.
Summary
Work on the biological control of St. John's wort (Hypericum perforatum L.) in Australia first commenced almost seventy years ago, and has passed through a number of discrete phases, leading up to the current program of work. A total of 15 agents have been studied in some detail with a view to introduction, and 12 of these were eventually released. Six agents became established, four during earlier phases of work in the 1930s to 1950s and two in the current phase of work from the mid 1970s on. Two of the original agents to establish, the defoliating chrysomelid beetles Chrysolina quadrigemina and C. hyperici, provide some degree of control in certain situations, but are unable to prevent the continued spread of the weed. There is, however, some early evidence that the recently released eriophyid mite, Aculus hyperici, can cause substantial reduction in the vigour of St. John's wort populations and might therefore improve the overall level of biological control. This paper looks at the history of introductions of agents into Australia in the context of changing strategies for biological control of the target weed, and looks at the potential for further introductions of new agents. Whether further work is required, however, depends on the eventual impact of A. hyperici, and the need for careful evaluation of this agent is stressed.
Plant Protection Quarterly (1997) 12 (2) 73-80.