Lesson 3: Conducting Pest Risk Assessment for Trade
Topic 2: Pest Categorization
Pest categorization is the next step in the PRA process. In this step, the analyst identifies potential quarantine pests or regulated nonquarantine pests. This topic presents the need for this step and discusses relevant pest definitions.
Objectives:
- Be able to define pest categorization and describe the steps involved with this process
- Apply the concept of regulated pest and quarantine pest to pest categorization
The Need for Pest Categorization
Recall that, according to ISPM No. 2 and No. 11, PRA includes three basic stages. The second stage of PRA, pest risk assessment, begins with pest categorization. The analyst proceeds to this step if it has been determined in the first stage that an organism (or organisms in the case of a pathway assessment) should be assessed further.
Pest categorization is “the process for determining whether or not a pest has the characteristics of a quarantine pest or those of a regulated non-quarantine pest” (e.g., a regulated pest).
The pest categorization step usually involves a simple assessment to determine whether the pests identified in the initiation stage meet the criteria for being regulated pests. Usually, this means briefly examining evidence to determine whether a pest occurs in the PRA area (for quarantine pests), if a pest would be able to survive in the PRA area, and if a pest has the potential to cause economic harm. If evidence indicates a pest meets these criteria, the pest risk assessment continues to the next step.
If, however, evidence indicates that the pest is not likely to cause unacceptable economic harm or if it indicates that the pest is unlikely to become established in the PRA area, then the pest risk assessment can be stopped at this point.
In the case of a pathway assessment, the pest categorization step also examines whether pest(s) identified in the initiation stage are likely to be associated with the specified pathway. For instance, if the specified pathway is citrus fruit, only those pests likely to be associated with the fruit should be further analysed. Other pests, such as those that are associated with other parts of the plant or those that are not associated with imported plant parts, generally would not be analysed further. (Some might be analysed further, but only if it were technically justified.)
The pest categorization step is a unique aspect of PRA, setting it apart from risk assessments conducted for other purposes (e.g., food safety or environmental assessment). This step is necessary because a determination must be made as to whether the pest(s) are regulated by the country doing the PRA. If the analyst finds that the pests occur in that country already and are not managed or controlled—that is, if those pests are not regulated pests—then the PRA is stopped.
The Result of Pest Categorization
The pest categorization stage ends with a recommendation regarding the next steps to be taken.
Pests that are categorized as quarantine pests and that are likely to follow a pathway for entry are subject to further assessment. (For the purposes of this module, we will focus on the assessment of quarantine pests since regulated nonquarantine pests are rarely assessed in practice.) As in the initiation stage, analysts are advised to clearly document all of the evidence used to support judgments.
Case Study Example
Let’s return to our assessment of Pestis horribilis. In the initiation stage, we concluded that this pest is indeed a hazard. Now, you must determine if it meets the criteria for a quarantine pest.
The answers to the following four questions will help you decide whether or not to continue the PRA—that is, categorize Pestis horribilis as a quarantine pest. Be sure to base your answers on the most current information available.
- Is the pest present in the PRA area?
- What is the regulatory status of the pest if it is present in the PRA area?
- Is there potential for entry and spread of the pest within the PRA area?
- What are the potential economic consequences in the PRA area?
The IPPC defines quarantine pest as “a pest of potential economic importance to the area endangered thereby and not yet present there, or present but not widely distributed and being officially controlled” [FAO, 1990; revised FAO, 1995; IPPC 1997].
Identification of the endangered area within a PRA area is determined in the potential for entry and spread. The endangered area could be the whole PRA area or part of it. The IPPC defines endangered area as “an area where ecological factors favour the establishment of a pest whose presence in the area will result in economically important loss” [FAO, 1995].
The following is a combination of both questions you need to answer and questions you should consider. Use information gathered from these questions to determine if Pestis horribilis should be categorized as a quarantine pest. Each time you encounter a pest with potential to be categorized as a quarantine pest, use these questions to help determine whether or not a PRA needs to be performed.
What is the regulatory status of the pest if it is present in the PRA area?
If the pest is already widely distributed in the PRA area, then the PRA stops because it is too late to keep it out. This situation does not apply to Pestis horribilis and Importland.
If the pest is already present in the PRA area, there are two situations in which the PRA could continue:
- The pest is not yet widely distributed
- There is an official program in place to eradicate the pest
For example, if Pestis horribilis managed to escape into one tamola field but was not found elsewhere, it would be important to contain the pest to that field if possible. Your chances of containing and eliminating a pest are much better with early detection and quick implementation of control and containment actions determined from the PRA. The pest would need to be under official control or soon to be under official control for the PRA to continue.
The IPPC defines official control as “the active enforcement of mandatory phytosanitary regulations and the application of mandatory phytosanitary procedures with the objective of eradication or containment of quarantine pests or for the management of regulated non-quarantine pests” [ICPM, 2001].
Is there potential for entry and spread of the pest within the PRA area?
The potential for a pest to be introduced, establish itself, and spread requires that the whole or parts of the PRA area meet these conditions:
- Ecological or climatic conditions suitable for the entry and spread of the pest
- The presence of suitable hosts (including near relatives), alternate hosts, and vector, if needed
If your brief examination of conditions within the PRA area determines that these conditions do not allow for the entry and spread of the pest, then you cannot categorize the pest as a quarantine pest and the PRA stops. But if there is evidence of potential for entry and spread of the pest within the PRA area, then the PRA continues.
What are the potential economic consequences in the PRA area?
A brief examination of the information gathered in the initiation stage will help you determine if the organism is likely to cause unacceptable harm to cultivated or naturally occurring host plants in the PRA area. If you do not find evidence of potential harm, then you cannot categorize the pest as a quarantine pest and the PRA stops. But if you find evidence of potential for unacceptable harm, then the PRA continues.
Conclusion of Pest Categorization
All of the information you have gathered indicates that Pestis horribilis meets the criteria to be a quarantine pest. That means you should continue the PRA process. Now you must conduct a more detailed assessment of the probability of pest entry and spread and a thorough assessment of potential economic consequences.
Pest categorization is the first step in the pest risk assessment stage. Pest categorization is “the process for determining whether or not a pest has the characteristics of a quarantine pest or those of a regulated non-quarantine pest” (e.g., a regulated pest). This must be done first in order to determine whether or not completing a PRA is necessary.
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