Selecting biological control agents

Introduction

This is a selective review of the literature concerning the current state of knowledge about those principles and practices of biological control that are relevant to making an application to the EPA to introduce an exotic biological control agent into New Zealand. It does not cover issues relevant to genetically modified organisms, or to required Maori consultation. It covers the selection and pre-release evaluation of effective and safe agents, be they insects, other arthropods, phytophages, parasitoids, predators, or pathogens of plant and insect pests. It also reviews what we know about assessing the non-target effects of biological control agents on ecosystems and provides some avenues for thinking about these issues. Its purpose is to help applicants to more easily and more completely address the issues that are of importance to the regulator, and hence to environmental, social and cultural biosafety.

The EPA determines whether an agent should be released by weighing the potential benefits of introduction against the potential risks and costs. Applicants can maximise that benefit to cost ratio by:

selecting the agent or agents best able to reduce the adverse effects of the target;
knowing how well agent populations will establish, grow and spread;
identifying what the host range of the agent is likely to be and then testing that hypothesis;
analysing the likely interactions between the agent and its new ecosystem;
describing the environmental and ecological benefits of releasing the agent in New Zealand.

The biology and ecology of both targets and potential control agents are hugely diverse, and a 'one-size-fits-all' approach to advice on the selection and development of control agents is not possible (van Driesche 2004). It is unlikely that a prospective applicant will find a perfect model for a proposed biological control project because there is usually too little known and too much diversity. The HSNO process acknowledges that the outcome of a risk/cost/benefit assessment will be uncertain because our knowledge of both the agent and the target are imperfectly known, and because ecosystem responses in the new range cannot be known precisely. The EPA makes decisions in the face of this uncertainty. However, the comfort level of the Authority, and the prospects for a successful application, can be improved considerably by identifying and quantifying those uncertainties, by providing relevant information from parallel projects, and by demonstrating care and attention to the ecological complexity that is inherent in any application. This review facilitates access to theoretical discussions and case studies which will hopefully assist an applicant to consider all relevant facts before applying to import a particular biological control agent.

References

van Driesche R. (2004). Predicting host ranges of parasitoids and predacious insects - what are the issues? Pp. 1-3 In: Assessing host ranges for parasitoids and predators used for classical biological control: a guide to best practice, R. Van Driesche and R. Reardon (Ed.) USDA Forest Service, Morgantown, West Virginia.