Pest risk analysis- introduction, types and methods
Pest Risk Analysis (PRA) is a science-based process used by national plant protection organisations (NPPOs) to evaluate evidence to determine if an organism is a pest, whether it should be regulated, and what phytosanitary measures are needed to prevent its introduction and spread.
Introduction to Pest Risk Analysis
The primary purpose of a PRA is to provide technical justification for import regulations and other phytosanitary measures to protect a country's plant resources, agriculture, horticulture, forestry, and environment from potential damage. It is a requirement for international trade under the International Plant Protection Convention (IPPC) and the World Trade Organization's Agreement on the Application of Sanitary and Phytosanitary Measures (SPS Agreement).
The PRA process is not necessarily linear and involves ongoing information gathering, documentation, and risk communication throughout its stages.
Types of Pest Risk Analysis
PRA can be categorised based on how it is initiated and the specific focus of the analysis:
Pathway-initiated PRA: This is triggered by a new or existing pathway, such as a new trade in a specific commodity (e.g., imported plants or plant products), packing materials, or natural spread, to identify potential pests associated with it.
Pest-initiated PRA: This occurs when a specific pest is identified as a potential threat (e.g., a new outbreak is detected, or a pest is repeatedly intercepted), and an assessment is needed to determine if it should be regulated.
Policy-initiated PRA: This type is prompted by a need to review or revise existing phytosanitary policies or regulations, often due to new scientific information, a change in a country's pest status, or a trade dispute.
In terms of methodology, PRAs use both qualitative (subjective judgment and descriptive categories like "low," "medium," "high" risk) and quantitative (numerical data and statistical modelling) approaches, depending on the available information and data.
Methods (Stages) of Pest Risk Analysis
According to the IPPC International Standards for Phytosanitary Measures (ISPM 2 and ISPM 11), a PRA is structured into three main stages:
Stage 1: Initiation
The goal is to identify the pest(s) and pathways of concern and define the area to be protected (PRA area).
Key steps include:
Determining if the organism in question meets the IPPC definition of a "pest".
Gathering initial information on the pest's identity, distribution, and association with host plants or commodities.
Stage 2: Pest Risk Assessment
This stage evaluates the probability of the pest's introduction, establishment, and spread, as well as its potential economic and environmental consequences.
It consists of three steps:
Pest Categorization: A quick assessment to determine if the pest satisfies the criteria of a quarantine pest (not yet present or not widely distributed and under official control, with potential economic importance).
Assessment of Probability of Introduction and Spread: This involves evaluating the likelihood of the pest's entry via specific pathways and its ability to survive, establish, and spread in the new environment, considering factors like climate suitability and host availability.
Assessment of Potential Consequences: This step identifies the potential impacts, including direct effects (crop loss, damage) and indirect effects (market access issues, control costs, environmental changes).
Stage 3: Pest Risk Management
If the risk is deemed unacceptable, this stage identifies, evaluates, and selects appropriate phytosanitary measures to reduce the risk to an acceptable level. Measures must be technically justified and the least trade-restrictive possible and may include:
Inspections and testing of consignments.
Specific treatments (chemical, thermal).
Prohibition of certain commodities.
Production in pest-free areas or under certification schemes.