ReviewProgress in risk assessment for classical biological control
Introduction
In this contribution, we summarize recent developments in research on biosafety of biological control. We start by discussing briefly the history of research in this area, through a period of controversial debate to a realization that the efficacy of biological control as well as the environmental safety of the outcome can benefit considerably from a robust pre-release risk analysis, an ecological approach to the selection of biological control agents and post-release monitoring of target and non-target impacts. We then examine recent research advances in the areas of biological control agent selection and characterization, and provide some detail of current advances in laboratory testing for host range prediction, an area that is central to risk analysis for regulators. We discuss post-release assessments of biocontrol safety, and recent advances in predictive modeling of population impacts of biological control agents. The paper focuses particularly on research that has been carried out in New Zealand and Australia, and we conclude with a section on the regulatory process in New Zealand, and how well this has performed over the first 10 years of its implementation.
Section snippets
The biosafety controversy
Research on biological control flourished after the publication in 1963 of the book ‘Silent Spring’ (Carson, 1963), which alerted the public to the environmental and human health dangers of pesticide use. In the aftermath of this book demands were made that pesticide use be scrutinized and safer alternatives found. In the book, Rachel Carson examined and promoted the use of biological control and other alternative technologies. Biological control was suddenly seen as the ‘magic bullet’, and it
Agent selection and characterization
The aftermath of the biosafety controversy has seen increased emphasis on selecting biological control agents that are likely to be highly effective at reducing the population densities of the target pest or weed, but that are unlikely to impact on non-target species. Efforts to characterize suitable agents have been hampered by the complexities of pest–enemy interactions, though recent successes with multi-factorial approaches (e.g. Lynch et al., 2002) suggest that further progress may be
Host range prediction
Approaches have changed dramatically from earlier times when natural enemies were deliberately selected because they were not host specific, so that reservoir populations of the biological control agent could be maintained on non-target species for periods when the target pest was scarce. It is no longer acceptable for polyphagous biological control agents to be seen as usefully “lying in wait” ready for an opportunity to parasitize or prey on a pest when outbreaks occur (Murdoch et al., 1985).
Post-release assessments of biological control safety
Post-release investigation of non-target impacts of earlier biological control agent introductions, sometimes coupled with retrospective laboratory testing, have been particularly informative for early releases which pre-dated the current requirement for rigorous risk assessment. Louda et al. (2003) reviewed some key biological control case histories and concluded that host-specificity testing has generally been adequate for determining physiological host range, but falls short on predicting
Measuring impacts
In evaluating the consequences of biological control it is important to identify exactly which impacts are important. We might consider the economic costs of the target species or economic values of non-targets, cultural or esthetic values of the species, or their ecosystem function, but in the vast majority of cases the ultimate measure of impact is the effect of a biological control agent on the population sizes of target and non-target species. Nevertheless, population-level impacts are
Testing a regulatory process in New Zealand
In 1998 the Hazardous Substances and New Organisms (HSNO) Act came into force, requiring approval from the Environmental Risk Management Authority (ERMA) for any deliberate release of new organisms into the New Zealand environment. By definition all new organisms, including biological control agents, are considered a hazard and must be subjected to a risk assessment before approval for release can be given. Formerly the introduction of new biological control agents had been administered by the
Challenges for the future
An enormous amount has been achieved in the last 20 years not only in research and regulation relating to biological control, but also in easing the tension between biological control practitioners and those with strong concerns about biosafety. We anticipate that in the future there may be a greater emphasis on balancing efficacy with biosafety, and that biological control agent biotypes will be selected to optimize these characteristics. Indeed, perhaps in the future we will be able to
Acknowledgments
We thank the organizers of the ANZ Biocontrol Conference in Sydney in February 2008 for supporting in part the attendance of F.G.H., and for the opportunity to assemble our contributions into this paper; this work was partially funded by New Zealand’s Foundation for Research, Science & Technology through contract CO2X0501, the Better Border Biosecurity (B3) programme (www.b3nz.org).
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