European and Mediterranean Plant Protection Organization, 1 rue Le Notre, Paris, France

Within the present century, most countries of the world have developed phytosanitary (= quarantine) regulations that are applied to imports of plants and plant products (but also to some other types of traded commodities) in order to prevent the introduction of exotic plant pathogenic organisms into their territories. Such regulations generally include quarantine lists of prohibited pests and certain restrictions on imports. The decisions as to which pests should be included in quarantine lists was generally based on the advice of national experts, but, as no consistent criteria were available to aid these decisions, the justification for taking phytosanitary measures was often questioned.

In 1994, the member countries of the World Trade Organization completed the Agreement on the Application of Sanitary and Phytosanitary Measures (SPS Agreement) which had the aim of preventing the use of phytosanitary regulations as disguised barriers to international trade. The SPS Agreement recognizes that countries have the right to apply phytosanitary regulations to protect their territories against the introduction of certain pests, but (i) the risk from each pest must be scientifically determined, and (ii) the measures used must be no greater than necessary to reduce the risk to an acceptable level. In order to decide which pests should be covered by phytosanitary regulations and which measures should be applied, a scientifically based analysis of risk should be used. As a consequence of the SPS Agreement, the development of the subject of pest risk analysis (PRA) has accelerated in recent years, and decision-making schemes on pest risk assessment and pest risk management have been published or are in development in many parts of the world. Such schemes guide the assessor through the essential questions that should be answered in order to reach an acceptable assessment of risk. They seek to determine whether and how probable it is that a particular pest could be transported by international trade, that it could enter and establish in a particular area and that it would be likely to produce a significant economic impact; if the answers to these questions lead to the conclusion of an unacceptable risk, a pest risk management scheme would assist in deciding which phytosanitary measures could be applied. However, in order to answer the questions, it is essential to have a considerable body of information about the distribution, biology, host-parasite relationships and economic impact of the pest. Such information is not always available or reliable for exotic pests and there is, therefore, an urgent need to focus research towards obtaining the appropriate data to conduct adequate PRAs.