United States

Department of

Agriculture

Animal and

Plant Health

Inspection

Service

Plant Protection 

and Quarantine

Agency Contact

Plant Epidemiology and Risk Analysis Laboratory

Center for Plant Health Science and Technology

United States Department of Agriculture

Animal and Plant Health Inspection Service

Plant Protection and Quarantine

1730 Varsity Drive, Suite 300

Raleigh, NC 27606

Guidelines for Plant Pest 

Risk Assessment of 

Imported Fruit & 

Vegetable Commodities
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Department of Agriculture.

First Edition Issued 2012
08/2012-01 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities TOC-1

Contents

Section TOC: Contents ........................................................TOC-1

Section TOC: List of Procedures ........................................TOC-3

Section 1: Introduction & Framework.....................................1-1

Introduction ........................................................................................... 1-1

Pest Risk Analysis Framework ............................................................ 1-2

Stages of pest risk analysis ................................................................... 1-2

The Legal Framework for PRA ........................................................... 1-4

International guidelines for considering economic impacts in PRA .. 1-10

National legislative framework for PRA ............................................ 1-14

Climate change in PRA ...................................................................... 1-17

Overview of the PPQ Risk Assessment Model for Commodity Imports 

for Consumption ........................................................................... 1-18

Overview of the model ....................................................................... 1-18

Volume of consignments consideration .............................................. 1-20

Pathway considerations ...................................................................... 1-20

The endangered area ........................................................................... 1-22

Likelihood of introduction .................................................................. 1-22

Potential consequences of introduction .............................................. 1-22

Uncertainty analysis ............................................................................ 1-23

Overall risk rating ............................................................................... 1-24

Risk mitigation documentation ........................................................... 1-25

Summary of processes ........................................................................ 1-25

Section 2: Conducting Pest Risk Assessment in PPQ .............2-1

Stage 1: Initiation .................................................................................. 2-1

Process 1: Documenting the initiating event and scope ....................... 2-2

Process 2: Determining if a weed risk assessment for the commodity is 

needed ............................................................................................ 2-4

Process 3: Defining the pathway .......................................................... 2-6

Process 4: Creating the pest list and pest categorization ...................... 2-9

Stage 2: Pest Risk Assessment ........................................................... 2-20

Processes in PPQ commodity import risk assessment ........................ 2-20
Contents

TOC-2 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-01

Risk elements evaluated in PPQ commodity import risk assessment .2-20

Process 5: Collecting information and defining the endangered area .2-22

Process 6: Assessing uncertainty for risk elements .............................2-33

Process 7: Assessing the likelihood of introduction ............................2-35

Process 8: Assessing potential consequences of introduction .............2-50

Process 9: Summarizing the final risk ratings and uncertainty ...........2-63

Stage 3: Risk Management ................................................................. 2-64

Risk Management in pest risk analysis ...............................................2-64

Uncertainty in risk management .........................................................2-66

Process 10: Risk mitigation notes .......................................................2-67

Section 3: Supplements and References ...................................3-1

Supplement 1: WTO Disputes ............................................................. 3-1

Supplement 2: Plant Hardiness Zones Area and Population Analysis ..

3-8

Supplement 3: Host Status ................................................................. 3-10

Host status issues in PRAs ..................................................................3-10

Scope and purpose ...............................................................................3-10

Key issues ............................................................................................3-11

Terminology ........................................................................................3-12

Evidence and information sources ......................................................3-16

Interpreting evidence to determine host status ....................................3-19

Background .........................................................................................3-19

Relationship of host status to risk .......................................................3-23

Examples, exceptions, and uncertainty ...............................................3-24

Appendix A: Recommendation for Prunus persica varieties to be considered non-hosts for Bactrocera cucurbitae ....................................3-27

Supplement 4: Evaluation of Evidence ............................................. 3-29

Literature Cited .................................................................................. 3-33
08/2012-01 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities TOC-3

List of Procedures

Procedure 1-1. Determining if a new or revised risk assessment is needed 2-2

Procedure 1-2. Documenting the initiating event ........................................ 2-3

Procedure 2-1. Determining if a weed risk assessment for the commodity is 

needed ............................................................................................... 2-4

Procedure 3-1. Defining the pathway .......................................................... 2-7

Procedure 4-1. Identifying potential pests for the pest list ........................ 2-11

Procedure 4-2. Optional: Determining whether a pest is actionable ......... 2-12

Procedure 4-3. Determining whether to include an actionable pest on the list .

2-13

Procedure 4-4. Completing the pest list table ........................................... 2-15

Procedure 4-5. Handling organisms identified only to genus level .......... 2-18

Procedure 5-1. Determining the order of analysis ..................................... 2-28

Procedure 5-2. Defining the endangered area ........................................... 2-29

Procedure 6-1. Assessing uncertainty for each risk element ..................... 2-34

Procedure 7-1. Assessing the likelihood of entry (Risk Element A) ........ 2-36

Procedure 7-2. Determining the likelihood of establishment (Risk Element B) 

2-42

Procedure 7-3. Determining the combined likelihood of establishment ... 2-47

Procedure 7-4. Determining the overall likelihood of introduction .......... 2-49

Procedure 8-1. Determining the potential direct impacts (Risk Element C) . 2-

52

Procedure 8-2. Determining if the pest is likely to cause unacceptable direct 

economic impacts ........................................................................... 2-58

Procedure 8-3. Additional analysis for pests with undetermined trade impact .

2-59

Procedure 8-4. Determining potential trade impacts ................................. 2-60

Procedure 9-1. Summarizing the final risk ratings and uncertainty .......... 2-63
08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-1

Section

1

Introduction & Framework

Introduction

In this document, we provide guidance for conducting commodity pest risk 

assessments in the United States Department of Agriculture (USDA), Animal 

and Plant Health Inspection Service (APHIS), Plant Protection and Quarantine 

(PPQ). The purpose of commodity pest risk assessment is to determine

1. the plant pest risk associated with fruit and vegetable commodities 

imported into the United States for consumption and 

2. the phytosanitary measures that may be used to mitigate the risk. 

Risk assessments are conducted by PPQ under the regulatory authority 

provided in Title IV—Plant Protection Act of 2000 (7 U.S.C. § 7701-7786, 

2000) and in conformity with PPQ’s responsibilities as the national plant 

protection organization (NPPO) for the United States under Article IV.2.f of 

the International Plant Protection Convention (IPPC).

Pest risk analysis (PRA) is the process used by NPPOs as the technical 

justification for phytosanitary measures. PRA is defined by the IPPC as “the 

process of evaluating biological or other scientific and economic evidence to 

determine whether a pest should be regulated and the strength of any 

phytosanitary measures to be taken against it.” The process requires a risk 

assessment to characterize the risk and risk management to determine 

appropriate measures. 

In this document, we provide guidelines for PPQ risk analysts conducting 

commodity import pest risk assessments, as well as for stakeholders and 

trading partners interested in understanding our methodology and rationale. 

The process we describe here is used to inform risk management, but does not 

include the risk management analysis. 

This document supersedes Guidelines for Pathway-Initiated Pest Risk 

Assessments, Version 5.02 (PPQ, 2000). Information covered here includes

an overview of pest risk analysis as outlined by the IPPC,

the legal framework for conducting pest risk analysis, and

specific guidelines for conducting commodity import pest risk 

assessments for APHIS-PPQ. 
Introduction & Framework

Pest Risk Analysis Framework

1-2 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 8/2012-1

These Guidelines are based on a qualitative methodology for assessing the 

likelihood and consequences of pest introduction and spread. Conclusions are 

expressed as relative rankings based on scientific, technical, and operational 

evidence and uncertainty. Basic information required by the USDA for 

initiating the process is found in the Prerequisite Rule (7 CFR § 319.5, 

Requirements for submitting requests to change the regulations).

These Guidelines will be updated as needed to incorporate corrections and 

improvements. All changes will be logged in Supplement No. 5.

Pest Risk Analysis Framework

Pest risk analysis (PRA) is “the process of evaluating biological or other 

scientific and economic evidence to determine whether an organism is a pest, 

whether it should be regulated, and the strength of any phytosanitary measures 

to be taken against it” (IPPC, 2012). 

PPQ’s risk assessment procedures are consistent with the International 

Standards for Phytosanitary Measures (ISPMs) adopted by IPPC as follows:

No. 1, Phytosanitary principles for the protection of plants and the 

application of phytosanitary measures in international trade

No. 2, Framework for pest risk analysis

No. 11, Pest risk analysis for quarantine pests including analysis of 

environmental risks and living modified organisms, and supplements

The use of biological and phytosanitary terms in these guidelines conforms to 

ISPM No. 5, Glossary of Phytosanitary Terms (IPPC, 2012). We discuss these 

standards in more detail in the IPPC Standards related to risk analysis section.

Stages of pest risk analysis

The IPPC describes three stages of pest risk analysis in ISPMs No. 2 and 11: 

initiation, risk assessment, and risk management.

Initiation

The first stage of pest risk analysis, initiation, involves defining the hazards by 

identifying the pest(s) and conditions that are of concern and should be 

considered for risk analysis. 

Initiation points include:

Identification of pathway(s). A pathway, often an imported commodity, 

is identified as a means for the introduction and/or spread of pests. A 

pathway other than commodity import could be identified (natural spread, 

packing material, mail, garbage, compost, passenger baggage, etc.).
Introduction & Framework

Pest Risk Analysis Framework

1-3 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Identification of pests. A specific pest requires evaluation. For example, 

this may be the result of a pest detection or interception, because a pest is 

being imported (e.g., biocontrol organism), because the organism 

previously was not known to be a pest, or because there was a change in 

the status or incidence of a pest in the PRA area. The results of initiation 

are clearly identified hazards (pests, pathways, or conditions), which 

become the focus for risk assessment.

Review of policies. Regulatory policies or operations require evaluation, 

for example, to revise regulations or requirements; to prioritize risk 

management activities; if a new system, process, or procedure is 

introduced; if new information is made available that could influence a 

previous decision; or if an international dispute on phytosanitary 

measures arises.

Pest risk assessment

Stage 2 of pest risk analysis is pest risk assessment: the evaluation of the 

probability of the introduction and spread of a pest and the magnitude of the 

associated potential economic consequences (IPPC, 2012). 

Risk assessment begins by first determining which pests to assess and then 

evaluating these pests for the likelihood and consequences of their introduction 

and/or spread. Risk assessment is composed of two distinct phases:

Pest categorization. A preliminary screening of individual pests to 

determine whether or not the pests meet the defining criteria for a 

quarantine pest or regulated non-quarantine pest.

Risk assessment. The examination and analysis of biological and 

economic information to estimate the potential for introduction and 

spread and the potential economic impact of the pests

Pest risk management

Stage 3, pest risk management, is the evaluation and selection of options to 

reduce the risk of the introduction and spread of a pest (IPPC, 2012). It results 

in a summary of options, including recommendations for the selection of 

preferred options. Options are assessed based on information about their 

efficacy, feasibility, and impacts.

The procedure in this stage is to identify and evaluate mitigation measures that 

may be used to reduce the risk. These may be existing measures or measures 

developed specifically for the conditions under consideration. 
Introduction & Framework

The Legal Framework for PRA

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-4

The Legal Framework for PRA

In this section of the guidelines, we provide an overview of the international 

and national legal framework for pest risk analysis. This framework provides 

the basis for why and how we conduct pest risk analysis, and creates a system 

of accountability for the conduct of pest risk analysis. In this section, we 

address 

The World Trade Organization and the IPPC, 

Relationship of the IPPC to the SPS,

IPPC Standards related to risk analysis,

The appropriate level of protection and the acceptable level of risk,

Provisional and emergency measures,

Precaution under the IPPC and SPS,

Rational relationship, 

Probable versus possible,

International guidelines for considering economic impacts in PRA

National legislative framework for PRA, 

Climate change in PRA, and

Relationship of the PPA to the WTO-IPPC framework.
Introduction & Framework

The Legal Framework for PRA

1-5 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

The World Trade Organization and the IPPC

The World Trade Organization (WTO) is the international organization 

responsible for establishing rules of trade. The rules are legally binding for its 

member nations. WTO agreements are the result of negotiations between WTO 

Members. Agreements are implemented by Members toward the objective of a 

non-discriminatory trading system based on agreed rights and obligations. 

Each Member can expect that its exports will be treated fairly and consistently 

in other Member countries and each Member country agrees to do the same for 

imports into its own country. The WTO Agreement on the Application of 

Sanitary and Phytosanitary Measures (the SPS Agreement; SPS WTO, 1995) 

covers requirements for food safety and the life and health of animals and 

plants. The SPS Agreement requires that restrictions be based on international 

standards or scientific principles and evidence, that they be applied only to the 

extent necessary to protect health, and that they do not arbitrarily or 

unjustifiably discriminate between countries where identical or similar 

conditions prevail. To achieve its objective, the SPS Agreement encourages 

Members to use international standards, guidelines, and recommendations 

where they exist, and identifies standard-setting bodies for food safety, animal 

health, and plant health. Members may adopt SPS measures that result in 

higher levels of health protection—or measures for health concerns for which 

international standards do not exist—provided that they are technically 

justified. Technical justification is accomplished by an assessment of risk 

taking into account scientific principles and evidence (technically justified). 

Article 2 of the SPS Agreement (Basic Rights and Obligations) and Article 5 

(Assessment of Risk and Determination of the Appropriate Level of Sanitary or 

Phytosanitary Protection) describe the central concepts. The IPPC is a 

multilateral treaty for international cooperation in plant protection, and is 

identified in the SPS Agreement as the standard-setting body for plant health. 

The Convention makes provisions for the application of measures by 

governments to protect their plant resources from harmful pests (phytosanitary 

measures) that may be introduced through international trade. The IPPC 

complements the SPS Agreement by providing the international standards 

recognized by the WTO to ensure that phytosanitary measures have a scientific 

basis for their placement and strength and are not used as unjustified barriers to 

international trade.

Article 5.1 of the SPS Agreement states that WTO Members “shall” ensure 

that phytosanitary measures are based on an assessment of risk. The agreement 

defines risk assessment as “The evaluation of the likelihood of entry, 

establishment or spread of a pest or disease within the territory of an importing 

Member according to the sanitary or phytosanitary measures which might be 

applied, and of the associated potential biological and economic consequences; 

or the evaluation of the potential adverse effects on human or animal health 

arising from the presence of additives, contaminants, toxins, or disease-causing 

organisms in food, beverages or feedstuffs.”
Introduction & Framework

The Legal Framework for PRA

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-6

Slightly different terminology is used in the IPPC (1997) and associated 

standards (e.g., ISPMs No. 2, 5, 11, and 21) to reflect the same concepts and 

obligations. Two terms that are particularly important are found in Article II 

(Use of terms):

Technically justified. Justified on the basis of conclusions reached by 

using an appropriate pest risk analysis or, where applicable, another 

comparable examination and evaluation of available scientific 

information. 

Pest risk analysis. The process of evaluating biological or other scientific 

and economic evidence to determine whether an organism is a pest, 

whether it should be regulated, and the strength of any phytosanitary 

measures to be taken against it (IPPC, 2012).

Despite the subtle differences in terminology, the SPS Agreement and the 

IPPC are clear that a systematic process for gathering, evaluating, and 

documenting scientific and other information is required to provide the basis 

for phytosanitary measures affecting trade. This involves consideration of 

economic as well as biological aspects of pest risk for plant health and life. 

Relationship of the IPPC to the SPS

These requirements of the SPS Agreement create a direct relationship between 

risk assessment and international standards, which are established by the 

relevant international organizations. The SPS Agreement states that a risk 

assessment is not required where measures are based on international 

standards. This is because the risk basis for the standard is already 

internationally agreed upon. Where standards do not exist or are deemed 

inappropriate, risk assessment is needed to provide the justification for 

measures. Another part of the relationship involves the standards developed for 

performing risk assessment. In both cases, the standard setting organizations 

play a significant role in providing governments with the means to justify their 

SPS measures. 

At this time, only a few specific phytosanitary standards can be used to directly 

support national measures in lieu of risk assessment. Therefore, where 

phytosanitary measures are concerned, WTO Member governments are largely 

forced to base their decisions on risk assessments. This means that the process 

used for phytosanitary risk assessment becomes extremely important to all 

countries. 
Introduction & Framework

The Legal Framework for PRA

1-7 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

IPPC Standards related to risk analysis

ISPM No. 2, Framework for Pest Risk Analysis (IPPC, 2007), was originally 

adopted by the IPPC in 1995 as Guidelines for Pest Risk Analysis and was 

revised in 2007. This standard has served for more than a decade as the 

primary conceptual and procedural reference for phytosanitary risk analyses. 

This standard provides basic background regarding risk analysis for 

phytosanitary purposes and outlines a three-stage process for conducting risk 

analysis. ISPM No. 2 has been widely used by NPPOs throughout the world as 

a reference outline for developing their phytosanitary risk analysis systems and 

processes.

ISPM No. 11, Pest Risk Analysis for Quarantine Pests, was adopted in 2001. In 

2003, the Interim Commission on Phytosanitary Measures (now the 

Commission on Phytosanitary Measures), the governing body of the IPPC, 

adopted a supplement on environmental risks, and in 2004, a supplement on 

genetically modified organisms was added (IPPC, 2004a). 

In 2004, ISPM No. 21, Pest Risk Analysis for Regulated Non-Quarantine Pests

(IPPC, 2004b), became part of the family of standards devoted to pest risk 

analysis. All of these standards provide significant detail regarding the 

concepts and practice of risk analysis. 

The appropriate level of protection and the acceptable level of risk

The SPS Agreement discusses the acceptable level of risk in terms of the 

appropriate level of protection. In phytosanitary terminology, the terms 

“negligible pest risk” and “quarantine security” are also commonly used. Other 

terms, such as insignificant risk, no significant risk, de minimus risk, and safety 

are also encountered occasionally in documents and discussions related to the 

same or similar concepts.

It is the sovereign right of an importing country to establish its appropriate 

level of phytosanitary protection. The appropriate level of protection (or 

acceptable level of risk) is not determined by the individual risk analyst but is 

instead determined by broader policy. 

In general terms the degree of risk1 accepted is commensurate with the benefits 

and costs of an alternative. This means that although the absolute risk of a 

particular pest might be significant, it may still fall within an acceptable level 

of risk (or alternatively, there may be an appropriate level of protection) if, for 

example, one of the following applies:

The benefits associated with accepting the risk are greater than any 

associated costs.

1 Risk in this context refers to the likelihood of pest introduction with unacceptable consequences.
Introduction & Framework

The Legal Framework for PRA

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-8

The risk mitigation costs are affordable.

The risk is below what is considered normal or allowable compared to 

existing risks that are being accepted.

The risk is unchangeable and therefore must be accepted.

The acceptable level of risk is not necessarily a “bright-line concept” and 

should not be expected to be static. The strength of the measures applied in 

response to the risk should be linked to sound and open criteria and the 

measures should be consistent, to the extent possible, with the strength of 

measures for similar situations.

Provisional and emergency measures

The SPS Agreement (SPS WTO, 1995) and the IPPC (1997) include concepts 

and terms for provisional and emergency measures that may not be well 

understood or aligned. Other instruments and organizations also refer to socalled “precautionary measures” that are variously understood and generally 

linked to the application of the “precautionary approach” (also sometimes 

known as the “precautionary principle”). 

Emergency measures are not explicit in the SPS Agreement but extend from 

Annex B paragraph 6 (urgent problems) and the resulting Emergency 

Notification format adopted by the SPS Committee (G/SPS/7 Rev 1). Article 

VII.6 of the IPPC is explicit about “emergency action” based only on the 

detection of a pest, indicating that such action will be evaluated (implying a 

PRA) as soon as possible to ensure that it is justified. The IPPC’s Principle 14 

(ISPM No. 1; IPPC, 2006) refers to emergency actions for new or unexpected 

phytosanitary situations based on a preliminary PRA and indicating that such 

measures “shall” be temporary and the subject of a detailed PRA as soon as 

possible. 

Provisional measures are referenced in Article 5.7 of the SPS Agreement. 

Based on the text of the SPS Agreement and relevant jurisprudence to date, 

such measures have the following characteristics:

They are taken in the absence of sufficient scientific evidence.

They are based on the available pertinent information (i.e., Members must 

search for and consider available evidence), including information 

provided by relevant international organizations (e.g., the IPPC), and 

information about measures applied by others.

They require that the Member imposing the measure actively pursue the 

information required for a more objective assessment of the risk and 

review of the measure within a reasonable period of time.
Introduction & Framework

The Legal Framework for PRA

1-9 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Precaution under the IPPC and SPS

The term “precautionary measures” is not explicitly used or described in either 

the IPPC or the SPS Agreement, although SPS jurisprudence indicates that 

provisional measures may “reflect precaution.” It may be argued, however, that 

phytosanitary measures are by their nature more or less precautionary 

depending on the influence of uncertainty in the judgment regarding 

acceptable risk. The concept of precaution based on uncertainty is therefore 

implicit in the application of proper risk analysis. 

Uncertainty and precaution have a direct relationship: the higher the 

uncertainty, the greater the need for additional precaution. A properly done risk 

analysis provides decision makers and stakeholders with a clear understanding 

of the information that may be lacking, the variability and possible error in the 

information used, and the significance of this uncertainty to the conclusions 

drawn. 

Two key points in understanding that the precautionary provisions for 

agricultural and environmental protection are in harmony must be made here. 

First, the precautionary approach, as described in the Rio Declaration, the 

Convention on Biological Diversity, and the Cartagena Protocol, is not 

necessarily incompatible with the IPPC or the SPS Agreement. The second 

important point is that these environmental agreements do not explicitly 

associate the application of the precautionary approach with the “failure” of 

risk analysis. Indeed, they are rather explicit about risk analysis as the basis for 

evaluating the available information. 

The question is whether a determination regarding the adequacy of information 

is made before risk analysis is undertaken or completed, or whether the risk 

analysis is completed and becomes the basis for identifying the uncertainty. 

This question also points to risk analysis as the starting point for dialogue on 

the issue and also the starting point for harmonization based on the realization 

of mutual goals for the protection of plant and environmental health from 

harmful pest invasion.
Introduction & Framework

The Legal Framework for PRA

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-10

Rational relationship

A key principle of risk analysis (although not described as such in either the 

IPPC or the SPS Agreement) is the concept of rational relationship. This 

concept has been a central issue in many SPS disputes and is rooted in the 

linkages between evidence and conclusions that are made implicitly or 

explicitly in both risk assessment and risk management. The concept has two 

components: (1) demonstrating an actual cause and effect relationship and (2) 

demonstrating that the magnitude of the response is reasonable. For example, 

there is no basis for assuming that root pests will be associated with fruit; 

therefore, any risk assigned to fruit for root pests or any measures that may be 

required would have no rational relationship from a cause and effect 

standpoint. The second element of rational relationship follows the idea that 

the strength of measures is proportional to the risk. The concept here is that the 

magnitude of the risk and the strength of measures applied to mitigate risk are 

on sliding scales. Higher risks correspond with stronger measures and vice 

versa. Measures do not have a rational relationship with the risk when they are 

misaligned based on other effective options that may be available. A simple 

example: a treatment designed for internally feeding arthropods may be overly 

rigorous for external feeders and contaminating pests. 

Probable versus possible

SPS jurisprudence has made an important distinction between the concepts of 

probable and possible. Numerous possible scenarios have been put forward in 

PRAs as the basis for events that represent risks without credible evidence that 

such events occur other than expert opinion and assumptions that they are 

possible. The results of disputes on this point clearly and consistently support 

the position that events that are relevant to risk analysis under the SPS 

Agreement must have a demonstrated probability and cannot only be possible.

International guidelines for considering economic impacts in 

PRA

Guidance found in international agreements and standards is somewhat 

ambiguous regarding how consequences of introduction should be evaluated, 

which can result in different interpretations by different countries.
Introduction & Framework

The Legal Framework for PRA

1-11 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Economic analysis guidance in the SPS Agreement

The SPS Agreement explicitly endorses consideration of risk-related costs 

(e.g., potential production or sales losses or control and eradication costs) in 

both assessing risks and managing risks through the choice of an SPS measure 

to protect animal or plant health. The language in the Agreement suggests that 

consideration of producer impacts alone would be sufficient to comply with the 

letter of the SPS Agreement, and that choice of an SPS measure is not required 

to be justified by an analysis of the effects on producers, consumers, taxpayers, 

and industries that use the regulated product as an input. 

Article 5.3 of the Agreement states:

“In assessing the risk to animal or plant life or health and determining the 

measure to be applied for achieving the appropriate level of sanitary or 

phytosanitary protection from such risk, Members shall take into account as 

relevant economic factors: the potential damage in terms of loss of production 

or sales in the event of the entry, establishment or spread of a pest or disease; 

the costs of control or eradication in the territory of the importing Member; 

and the relative cost-effectiveness of alternative approaches to limiting risks.”

In addition, Article 5.6 states that Members must ensure that their measures are 

not more trade restrictive than necessary to achieve their appropriate level of 

protection; however, what is meant by “not more trade restrictive than 

necessary” and whether this term has implications for economic consequence 

analysis in PRA is a matter of interpretation. 

IPPC guidance to economic consequence analysis in PRA

Several ISPMs (e.g., ISPMs No. 2, 5, and 11) either reference economic 

considerations or provide guidance that is applicable to economic analysis in a 

pest risk assessment. The overall importance of economic considerations in 

phytosanitary decision-making is suggested by the number of key 

phytosanitary concepts that reference economic terms. In ISPM No. 5, 

Glossary of phytosanitary terms (IPPC, 2012), the phrases “economic 

impacts” and “economic consequences” are explicitly mentioned in definitions 

of several important phytosanitary terms such as “pest risk,” “pest risk 

assessment,” “phytosanitary measure,” and “phytosanitary regulation.” 

“Economic importance” and “economically important losses” are explicitly 

mentioned in the definitions of other terms, including the definition for the key 

phytosanitary concept of “quarantine pest.” The glossary does not include a 

definition for any of the terms related to economic impacts or economic 

importance but does contain a supplement that provides guidelines for 

understanding them (IPPC, 2012, Supplement 2). 
Introduction & Framework

The Legal Framework for PRA

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-12

Supplement No. 2 to ISPM No. 5 (IPPC, 2012). The scope and purpose of the 

supplement is to provide clarification to ensure that economic terms are clearly 

understood and consistently applied and to illustrate certain economic 

principles as they relate to the IPPC’s objectives, in particular but not limited to 

environmental considerations. The supplement clearly states that the IPPC can 

account for environmental concerns in economic terms using monetary or nonmonetary estimates and that market impacts are not the sole indicator of pest 

consequences. 

Section 4 of the supplement to the glossary, Economic Considerations in PRA, 

discusses types of economic effects and costs and benefits. It describes a 

relatively inclusive approach to economic considerations in PRA, indicating 

that all economic effects (not just market related), both costs and benefits, and 

both direct and indirect effects, should be considered in PRA. It affirms the 

cost-benefit criteria for decision making, whereby policies should be pursued if 

benefits are at least as large as costs, and indicates that judgments about the 

preferred distribution of costs and benefits are a policy choice to be made 

outside the context of the economic analysis.

ISPM No. 2, Framework for pest risk analysis (2007a). ISPM No. 2 does not 

give specific guidance on how economic impacts should be conceptualized or 

measured, but describes the stages in a pest risk assessment and indicates 

where it is appropriate to consider economic factors:

Pest categorization: to determine whether a pest is “of potential economic 

importance.” 

Pest risk assessment: to assess potential economic impacts

Pest risk management: to determine whether or not appropriate 

phytosanitary measures to reduce pest risk to an acceptable level are 

available, cost-effective, and feasible. In addition, the ISPM indicates that 

PRA documentation should include evidence of economic impact

[emphasis supplied], and evaluation of risk management options.

ISPM No. 11, Pest risk analysis for quarantine pests, including analysis of 

environmental risks and living modified organisms (2004a). ISPM No. 11 

Section 2.3, Assessment of potential economic consequences, contains the most 

fully elaborated description of the process for assessing economic 

consequences in the pest categorization stage of a risk assessment, but contains 

such broad guidance that it leaves many questions unanswered about what 

should be measured and how it should be measured.

The guidelines discuss situations in which a detailed analysis of economic 

consequences may or may not be necessary. If it is widely agreed that pest 

introduction will have unacceptable consequences, detailed analysis may not 
Introduction & Framework

The Legal Framework for PRA

1-13 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

be necessary. On the other hand, it may be necessary to examine economic 

factors in greater detail when the level of consequences is in question, or when 

consequences are needed to evaluate the strength of measures, or to assess the 

relative benefits of exclusion versus control. 

The guidelines indicate that both direct and indirect effects of the pest should 

be identified and analyzed. In evaluating direct effects, which include effects 

of the pest on the potential host or the environment, the guidelines specify that 

the total crop area and/or potentially endangered area should be identified. 

Examples of direct effects on cultivated hosts could include crop losses, 

control measures, and effects on production practices. Direct effects of the pest 

on the environment could include reduction of keystone species or endangered 

native plants. Examples of indirect effects of the pest in the PRA area include 

effects that are not host-specific, such as effects on domestic and export 

markets (i.e., loss of export markets), changes to demand because of quality 

changes in the commodity, and social or other effects.

Summary SPS Agreement and ISPM guidance on economic 

consequences 

The SPS Agreement describes a more limited set of factors to be considered in 

economic assessments than do the ISPMs. This distinction is important 

because different approaches described in the SPS agreement and the ISPMs 

(i.e., estimating negative impacts to producers as opposed to estimating both 

costs and benefits) will affect what is measured, how results are interpreted, 

and could support different conclusions regarding risk management by 

decision makers. 

The SPS Agreement explicitly endorses consideration of risk-related impacts 

to producers in the importing country. The ISPMs describe a very broad range 

of approaches to economic consequence analysis in PRA, with ISPM No. 11 

emphasizing the inclusion of environmental impacts and endorsing a 

continuum of approaches ranging from “no detailed analysis” if consequences 

are widely viewed to be unacceptable, to qualitative analysis, to various 

approaches of quantitative analysis, which include consideration of relevant 

impacts on consumers, producers, and domestic and foreign markets. 

Based on available guidance in the SPS Agreement and the ISPMs, and in the 

absence of any clarifying WTO jurisprudence or case law, it may be concluded 

that risk assessment practitioners have considerable latitude in determining 

how to approach economic consequence analysis in PRA. This latitude would 

be subject to the conditions that any phytosanitary measures based on a risk 

assessment and economic consequence analysis should not violate the 

consistency provisions of the SPS Agreement by arbitrarily or unjustifiably 

discriminating between Members and should not be applied in such a way as to 

constitute a disguised restriction to trade.
Introduction & Framework

The Legal Framework for PRA

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-14

National legislative framework for PRA

The Plant Protection Act (PPA; 7 U.S.C. § 7701-7786, 2000) became law in 

June 2000 as part of the Agricultural Risk Protection Act. The PPA 

consolidates all or part of 10 USDA plant health laws into one comprehensive 

law, including the authority to regulate plants, plant products, certain 

biological control organisms, noxious weeds, and plant pests. The Plant 

Quarantine Act, the Federal Pest Act, and the Federal Noxious Weed Act are 

among the 10 statutes the new Act replaces. The PPA is necessary because of 

the major impact plant pests currently have and could have on the agriculture, 

environment, economy, and commerce of the United States. 

The following provisions of the PPA are important in relation to pest risk 

analysis associated with importations of plants and plant products: 

“...the Secretary shall publish for public comment a notice describing the 

procedures and standards that govern the consideration of import requests. The 

notice shall— 

1. specify how public input will be sought in advance of and during the 

process of promulgating regulations necessitating a risk assessment in 

order to ensure a fully transparent and publicly accessible process; and

2. include consideration of the following:

Public announcement of import requests that will necessitate a risk 

assessment.

A process for assigning major/non-routine or minor/routine status to 

such requests based on current state of supporting scientific 

information.

A process for assigning priority to requests.

Guidelines for seeking relevant scientific and economic information in 

advance of initiating informal rulemaking.

Guidelines for ensuring availability and transparency of assumptions 

and uncertainties in the risk assessment process including applicable 

risk mitigation measures relied upon individually or as components of 

a system of mitigative measures proposed consistent with the purposes 

of this title.”
Introduction & Framework

The Legal Framework for PRA

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Relationship of the PPA to the WTO-IPPC framework

From a legal standpoint, there is an important distinction to understand 

regarding differences between the Plant Protection Act (PPA)–our national 

authority for the implementation of plant protection programs and actions–and 

the WTO-IPPC framework, including all of the obligations, responsibilities, 

and guidance relevant to NPPOs such as PPQ. The legal ramifications for PRA 

are not the same and the terminology and concepts are not entirely consistent 

on many important points. 

One key difference regards the lack of consistency between the PPA concept of 

regulated pests and the WTO-IPPC concept of the same. The PPA provides the 

Secretary of Agriculture (APHIS by delegation) the authority to regulate any 

pest deemed to be harmful whether or not it meets the defining criteria of the 

IPPC. This authority is necessary for the USDA to implement programs for 

domestic pests (whether exotic, naturalized, or native). For example, the PPA 

does not link noxious weeds to quarantine pests in order to provide USDA with 

the flexibility to implement programs for domestic weeds. As a result, 

referring to “noxious weeds” in a PRA for imported articles represents a shift 

from the IPPC concept of a regulated pest (a quarantine pest or regulated nonquarantine pest) to the PPA concept, which may include the IPPC concept but 

is not limited to it. 

Another area where the WTO-IPPC framework must be interpreted against 

national policies is in the determination of pest status for purposes of pest 

listing in the PRA. The list of pests requiring analysis in the PRA should 

include all organisms for which the current national policy is to require 

phytosanitary measures (actionable pests). This includes organisms that meet 

the IPPC definition of a quarantine pest, but it also extends to other types of 

pests, including those that are established in the United States but are under 

consideration for official control and other pest taxa that for policy reasons are 

considered to require quarantine action. For example, taxonomic groups that 

are commonly intercepted in immature form and cannot be identified to 

species level may require action for the entire taxa (usually genus) because one 

or more species in that genus are quarantine pests. 

The reverse may also be true. Pests that meet the defining criteria for a 

regulated pest may not require action in all circumstances. For example, the 

current policy for armored scales that meet the internationally agreed criteria 

for a quarantine pest is to require action if associated with propagative material 

but not on fruit for consumption, because fruit is considered to be a negligible 

risk for introduction whereas plants are an excellent pathway. 

Other such differences exist that make it important for analysts to pay close 

attention to concepts and terminology in the PRA process. One way to do this 

is to think about the analysis from the standpoint of potential legal challenges. 
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The Legal Framework for PRA

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-16

A point that might be challenged in a U.S. court will be reviewed, argued, and 

ultimately judged against the authority of the PPA. A U.S. judge will have little 

interest in arguments based on the IPPC/WTO framework. Likewise, a 

challenge raised by a trading partner will be judged against the IPPC and the 

WTO, especially the SPS Agreement, where our domestic legal situation may 

have some bearing on the background but the central issue will ultimately be 

decided against the relevant international authority. 
Introduction & Framework

The Legal Framework for PRA

1-17 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Climate change in PRA

Climate change affects the ability of a plant pest to enter, establish, and spread 

in new environments. There are some challenges in making specific 

predictions about the effect of climate change on pest behavior. Members of 

the North American Plant Protection Organization’s (NAPPO’s) Pest Risk 

Analysis and Invasive Species Panels developed a discussion paper, Climate 

Change and Pest Risk Analysis (NAPPO, 2012), in which they considered 

issues related to climate change in PRA and identified several challenges.

The biggest challenge to effectively addressing climate change in PRA relates 

to the time horizon for climate change and the length of time for which a PRA 

is considered valid. Climate change models are generally based on projections 

of at least 20 years (Hellman et al., 2008), while PRAs often focus on a shorter 

time frame and may be updated when new information becomes available. Pest 

risk analyses represent the knowledge available at the time they were 

conducted—they are a “snapshot in time.” Consideration of future events and 

impacts is also limited to relatively short projections in time; however, the 

specific length of time that a given PRA is valid is not precisely defined. The 

time horizon for routine commodity PRAs is understood to be less than 20 

years, which is the time horizon for seeing effects of climate change. 

Therefore, it is beyond the scope of these Guidelines to attempt assessing the 

effect of climate change on pest behavior.

Furthermore, models used in PRA for predicting climate change and 

simulating the impact of climate change on species distributions may increase 

uncertainty to the point of compromising their utility. Climate change models 

usually address information at a global scale and may not be fine-tuned for 

predictions at the local or regional levels needed for most PRAs. 

In addition to the scientific challenges involved in considering climate change 

in PRAs, the SPS Agreement requires that measures be based on evidence and 

least trade restrictive. A risk assessment is intended to provide sufficient 

evidence that a chosen measure(s) is not arbitrary, unjustified, or a disguised 

barrier to trade. Therefore, climate change projections within a PRA must be 

sufficiently robust to meet these requirements. Specifically, sufficient scientific 

evidence is required to show a causal link between climate change and the risk 

being assessed. 

The interaction of climate change with changes in trade patterns will increase 

the need for new PRAs and for revision of existing ones to take into account 

changes in pest distribution and the likelihood of their associations with 

pathways (EFSA, 2007). However, the decision about whether or not to 

consider climate change scenarios or incorporate complex models into a PRA 

will depend on feasibility, goals, and the rigor of the available scientific 

support. Climate modeling can be complex, time-consuming, and resource-
Introduction & Framework

Overview of the PPQ Risk Assessment Model for Commodity Imports for Consumption

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-18

intense, and it may not be necessary to answer the question at hand.

Overview of the PPQ Risk Assessment Model for Commodity 

Imports for Consumption

Overview of the model

Risk is a product of the likelihood of an adverse event—in this case, a pest 

introduction—and the magnitude of the consequences. We separately rate the 

uncertainty during each process in the risk assessment and provide a summary 

of the uncertainties associated with the overall risk rating. In Figure 1-1, we 

depict the conceptual model for the process.
Introduction & Framework

Overview of the PPQ Risk Assessment Model for Commodity Imports for Consumption

1-19 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Figure 1-1. Processes overview. Procedures are in parentheses.
Introduction & Framework

Overview of the PPQ Risk Assessment Model for Commodity Imports for Consumption

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-20

Volume of consignments consideration

In these Guidelines, we do not include volume as an element to be rated. 

Although we recognize that volume can affect the level of risk (e.g., increased 

volume has the potential to increase risk), it is difficult, if not impossible, to 

accurately predict or control the volume of importations or the effect on risk. 

Following are some of the factors related to volume that can affect risk:

Seasonal timing of consignments (e.g., winter vs. summer).

Frequency and volume over time (e.g., a few large consignments vs. 

multiple small consignments).

Changes to the proposed frequency and volume of exports (both increases 

and decreases).

Proposed destinations for export markets.

Therefore, for the purposes of these Guidelines, we will use the volume 

proposed in the prerequisite information and assume that any proposal to 

export a commodity for commercial purposes will represent a significant 

enough volume of trade to affect risk. If the analyst judges, based on evidence, 

that changes in the initially proposed volume of trade will significantly affect 

risk, this will be noted in relation to risk management. This is particularly 

important if inspections are key to risk management.

Pathway considerations

Agricultural commodities move through different steps in international trade, 

from the field and packinghouses at the farm, through export-import brokers, 

to retailers and, finally, to consumers, and perhaps into the environment. While 

most pests may first become associated with the commodity (pathway) at the 

farm, pests may also enter or exit the pathway at any stage until arrival in the 

importing country or area (Figure 1-2). The risk of escape into a new 

environment does not begin until the commodity has arrived in the PRA area. 

This may be problematic when the pest treatment facility is located in the PRA 

area (as can be the case, for instance, with irradiation), before the risk is 

adequately mitigated. Most pests associated with commodities for 

consumption have a low likelihood for establishment.

Pest populations on agricultural commodities will generally decrease as 

commodities move through the process, particularly with effective postharvest processing measures (Figure 1-3). Increases in pest population size are 

rare and most likely would be associated with re-infestation or conditions 

conducive to the organisms’ growth and development during storage and 

shipping (e.g., pathogens, arthropods reproducing parthenogenetically). 
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Overview of the PPQ Risk Assessment Model for Commodity Imports for Consumption

1-21 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Figure 1-2. Pest presence on agricultural commodities can change as a result of 

harvest and post-harvest processing measures from harvest through 

shipping. This figure represents general harvest and post-harvest 

processes and is not intended to be comprehensive. 

Figure 1-3. An example of anticipated decrease in pest populations on commodities 

for export as they move through harvesting and post-harvest processing. 
Introduction & Framework

Overview of the PPQ Risk Assessment Model for Commodity Imports for Consumption

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-22

The endangered area

The area within the PRA area that has the identified biotic and abiotic 

conditions favorable for a pest’s establishment is identified as the “endangered 

area.” We define the area endangered by each pest by determining the portion 

of the PRA area where suitable hosts for that pest occur overlaid with portion 

of the PRA area where suitable environmental conditions also occur. Once a 

pest has entered the PRA area, it must be able to establish and subsequently 

spread in order for there to be consequences. The likelihood that a pest will 

establish (i.e., be able to survive, reproduce and/or perpetuate itself into the 

foreseeable future) is dependent on the pest overcoming biotic and abiotic 

resistance in a new area. Another way of stating that is that the pest must find 

suitable conditions in the PRA area to establish. Those conditions include 

biotic factors (availability of host material, presence or absence of natural 

enemies, etc.) and abiotic factors (e.g., temperature, season, humidity, rainfall 

or other environmental conditions that affect the ability of the pest to survive 

and reproduce). 

Likelihood of introduction

We qualitatively assess the likelihood of introduction as Negligible, Low, 

Medium, or High. The likelihood of introduction is based on the likelihoods of 

entry and establishment. The likelihood of entry depends on the pest being 

associated with the commodity and surviving or remaining with the 

commodity throughout the entire post-harvest and shipping processes. The 

likelihood of establishment depends on characteristics of the pest and 

suitability of the PRA area. The risk factors comprising the model for 

likelihood of introduction are interdependent and the relationship is therefore 

multiplicative. Thus, if any risk factor is rated as Negligible, then the overall 

likelihood will be Negligible. 

Potential consequences of introduction

We determine if the pest is likely to cause unacceptable impacts in the PRA 

area upon introduction by considering the potential direct and indirect impacts 

in relation to a hypothetical situation where the pest is supposed to have been 

introduced and to be fully expressing its potential economic consequences 

throughout the endangered area. This evaluation is made by obtaining 

information on the types of impacts currently being caused by the pest in areas 

where the pest occurs naturally or has been introduced. Spread potential is 

evaluated as a component of potential consequences because the expression of 

potential economic consequences depends on the rate and manner of spread in 

the PRA area. Our analysis of spread potential focuses on determining whether 

the pest is likely to be able to spread throughout the endangered area quickly 

enough to result in economically important losses. 
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Pests that are unlikely to cause unacceptable impacts are called “non-threshold 

pests” because their total impacts are not expected to reach the threshold of 

damage that would warrant additional phytosanitary measures within a 

reasonable period of time.

Uncertainty analysis

Estimating pest risk involves many uncertainties, in large part because 

assessors have to extrapolate from the current situation of the pest to a novel 

situation in the PRA area. Two major types of uncertainty in analyzing risk are 

(according to Merrick and van Dorp, 2006)

the randomness of the system itself, including natural variability (aleatory 

uncertainty) and

the lack of knowledge about the system (epistemic uncertainty).

Uncertainty due to variability among individuals is inherent in biological 

systems and should be measured or described. New or additional information 

will not usually reduce uncertainty arising from variability. Uncertainty due to 

lack of knowledge may be reduced by further study and data collection. In 

reality, the clear distinction between variability and uncertainty from lack of 

knowledge is not always possible to make and may be dependent on the 

context. Furthermore, most risk assessments deal with both types of 

uncertainty concurrently. The distinction between two types of uncertainty is, 

however, important when explaining model results to decision makers or the 

public and when expending resources for data collection.

Common sources of uncertainty include 

old/dated information,

conflicting information,

absence of information,

extrapolation of information available for congeneric organisms,

reliance on expert judgment and conflicting or vague opinions from 

experts, and

incorrect assumptions or models. 

Documenting the degrees and types of uncertainty in the assessment and 

indicating where expert judgment has been used is important. This increases 

transparency and may help identify and prioritize research needs. 

Separating the uncertainty that arises due to lack of knowledge from the ratings 

of risk elements is important; ratings should be based only on the available 

evidence, not the uncertainty associated with the evidence. For instance, a 
Introduction & Framework

Overview of the PPQ Risk Assessment Model for Commodity Imports for Consumption

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-24

given risk element should not be rated higher if there is a lot of uncertainty; 

rather, the rating should be assigned based on available evidence and the high 

level of uncertainty should be noted. At the same time, we recognize that a 

given risk element may be assigned a rating that may more or less accurately 

reflect the actual probability associated with that risk element, depending on 

the level of uncertainty. Higher levels of uncertainty could mean a given rating 

may be over- or under-estimating probability by one or more levels (e.g., a low 

rating with high uncertainty would truly be medium or high if we had more 

evidence on which to base our judgment). In cases with a high degree of 

variability, the analyst will typically make a conservative judgment resulting in 

a higher risk rating. This underscores the importance of describing 

uncertainty—including sources and magnitude—while at the same time 

maintaining judgments that are based on available evidence.

The feasibility of reducing uncertainty sources depends on the type of 

uncertainty, the possibility of gaining further data, and applying more reliable 

assessment methods. The application of quantitative uncertainty assessment 

(tiers 2 and 3 in EFSA, 2006) is generally recommended after the qualitative 

uncertainty assessment has been performed in order to point out the 

uncertainty sources for addressing later in the quantitative evaluation and for 

considering those uncertainties that cannot be quantified (Colyvan, 2008; 

EFSA, 2006).

Overall risk rating

The concerns of the public and most decision makers focus on events with dire 

consequences, even if these events have low probabilities of occurring. Yet, 

models have been helping to mask the criticality of catastrophic events by 

adhering to the expected value of risk, which intrinsically can equate a low 

probability of high-consequence events with a high probability of lowconsequence events. The reliance on this commonly used metric, when it is 

used as the sole measure of risk, can confuse the decision makers, leading to 

bad choices. The problem is that the expected value of risk is an operation that 

essentially multiplies the consequences of each event by its probability of 

occurrence and adds all these products over the entire probability range 

(Haimes, 2009). Transparency resulting from separating estimates of overall 

risk due to impact and due to likelihood allows implementation of mitigation 

measures that are most appropriate for each of the risks.

The overall pest risk is presented as a table depicting, for each individual pest, 

the specific risk rating for the likelihood of introduction, the determination of 

whether or not the pest is likely to cause unacceptable impacts, and the 

uncertainties associated with the ratings (see Process 9: Summarizing the final 

risk ratings and uncertainty for more detail). 
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Overview of the PPQ Risk Assessment Model for Commodity Imports for Consumption

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Risk mitigation documentation

Throughout the analysis, the analyst will collect information on both the 

pathway (e.g., the commodity being exported) and the pests. Much of the 

information gathered during risk assessment is also useful to risk management. 

Moreover, the risk assessment should inform and guide risk management 

(rather than simply act as a trigger), and the risk analyst is in the best position 

to provide information relevant to the development of risk management 

options. In Process 10: Risk mitigation notes, we provide more detailed 

guidance on the types of information gathered during risk assessment that are 

particularly relevant to risk management. We also provide a template and an 

example for communicating that information to risk managers.

Summary of processes

In Table 1-1, we summarize the main processes in the PPQ pest risk 

assessment model for commodity imports. Each process will be discussed in 

more detail in Conducting Pest Risk Assessment in PPQ. 

Process 7: Assessing the likelihood of introduction and Process 8: Assessing 

potential consequences of introduction can be performed in either order, as 

appropriate. Pests that have a Negligible likelihood of being introduced do not 

usually need to be assessed for consequences; similarly, pests that are unlikely 

to cause unacceptable economic consequences do not need to be analyzed for 

likelihood of introduction. Describing uncertainty is an important part of every 

process, but is explicitly assessed in terms of the risk ratings determined in 

Processes 7 and 8.

Table 1-1. Summary of the processes that comprise PPQ’s risk assessment model for commodity imports for 

consumption. 

Stage 1. Initiation

Process 1: Documenting the initiating event and scope. Describe the reason(s) for conducting the risk assessment 

and some of the background information regarding the proposed importation.

Process 2: Determining if a weed risk assessment for the commodity is needed.

Process 3: Defining the pathway. Describe the pathway based on information about the commodity, information provided by the exporting country regarding production practices, and processing of the commodity; state any assumptions.

Process 4: Creating the pest list and pest categorization. Compile a comprehensive list of all potential pests known 

to occur in the exporting country or region that are known to be associated with the host plant from anywhere in the 

world. Identify pests meeting criteria for further analysis. 

Stage 2. Pest Risk Assessment

Process 5: Collecting information and defining the endangered area. Gather the information necessary to complete 

the risk assessment (Processes 7 and 8). Based on available information, determine whether Process 7 or 8 should be 

completed first.

Process 6: Assessing uncertainty for risk elements.

Process 7: Assessing the likelihood of introduction. Estimate the likelihood of introduction (entry and establishment). Entry and establishment are evaluated as Risk Elements A and B, respectively. Pests that are rated Negligible at 

any stage do not need to be evaluated further.
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08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 1-26

Process 8: Assessing potential consequences of introduction. Determine if the pest is likely to cause unacceptable 

economic consequences. Direct impacts are evaluated as Risk Element C, and trade impacts are evaluated in Risk Element D.

Process 9: Summarizing the final risk ratings and uncertainty.

Stage 3. Risk Management

Process 10: Risk mitigation notes. Provide important information on pest biology, pathway, and uncertainty relevant to 

risk management.

Table 1-1. Summary of the processes that comprise PPQ’s risk assessment model for commodity imports for 

consumption. 

Stage 1. Initiation
08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-1

Section

2 Conducting Pest Risk 

Assessment in PPQ

Stage 1: Initiation

Initiation is the first stage of pest risk analysis and consists of defining the 

specific scope of the analysis and identifying the pests of concern that will be 

analyzed in the risk assessment. In PPQ commodity import risk assessment, 

the Initiation stage is completed using the following four processes (as outlined 

in the previous section in Table 1-1 on page 1-25): 

Process 1: Documenting the initiating event and scope

Process 2: Determining if a weed risk assessment for the commodity is 

needed

Process 3: Defining the pathway

Process 4: Creating the pest list and pest categorization

NOTE

As outlined in ISPMs No. 2 and 11, pest categorization is actually a part of pest risk 

assessment (Stage 2); however, for practical purposes the first part of pest categorization, determining whether pests are actionable, occurs as the pest list is developed (see Process 4: Creating the pest list and pest categorization on page 2-9). 
Conducting Risk Assessment in PPQ

Process 1: Documenting the initiating event and scope

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-2

Process 1: Documenting the initiating event and scope

In Process 1, we document why the risk assessment was initiated and describe 

its scope. In most cases, a risk assessment is initiated to evaluate the pest risk 

associated with a new importation request. Additional possible initiating 

events are listed in ISPMs No. 2 (IPPC, 2007) and 11 (IPPC, 2004a). The 

initiating event of the risk assessment must be documented, but before we 

initiate a risk assessment, we need to determine if the risk assessment is 

actually needed. If a previous risk assessment exists and adequately addresses 

the risks posed by the proposed commodity importation into the PRA area 

from the export area in question, the current risk assessment process may stop 

at this point.

Scoping is the process step during which the risk analysts and PPQ 

headquarters staff, usually during a conference call, determine the scope of the 

risk assessment. The scope of a risk assessment includes the commodity(ies) to 

be imported, export area(s), PRA area, field and/or harvest procedures to be 

considered when assessing pest risk, and other details that provide the basis for 

the risk assessment and all other subsequent decisions.

Procedure 1-1. Determining if a new or revised risk assessment is needed

Follow steps 1-3 to determine if a new or revised risk assessment is needed for the commodity.

Step 1 Determine whether any previous risk assessments have been completed for the requested or a sufficiently similar (neighboring country; close relative of plant species) commodity/country combination. If an assessment already exists, go to Step 2. If a new assessment is needed, go to Step 3.

Step 2 If a risk assessment already exists, determine whether it adequately addresses the current risks in 

question. Consider the following:

 Is the pest list complete?

 Have pest distributions or information on biology changed since that original risk assessment 

was completed?

 Have phytosanitary policies and/or regulations changed since that risk assessment was completed? 

If the existing risk assessment adequately addresses the risks posed by the proposed importation 

of the commodity, no new risk assessment needs to be initiated.

If a revised assessment is needed, go to Step 3.

Step 3 In the “Initiating Event” section of the risk assessment, briefly state the reason why a new or revised 

risk assessment is needed.

If a new or revised risk assessment is needed, continue to Procedure 1-2: Documenting the initiating event.
Conducting Risk Assessment in PPQ

Process 1: Documenting the initiating event and scope

2-3 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Procedure 1-2. Documenting the initiating event

State the following in the “Initiating Event” section of the risk assessment.

Name and affiliation of the requestor

Of the plant species to be imported: 

 the valid scientific name and common synonyms

 common name(s)

 cultivar/variety/race/etc. (if applicable)

 plant part(s) to be imported (e.g., root, fruit, leaf) 

 condition of the plant parts to be imported (fresh, dried, processed, etc.)

 seasonality of imports (if applicable)

The export and PRA areas

The reason why the risk assessment is needed (see Procedure 1-1: Determining if a new or revised risk assessment is 

needed). For example:

 The requested commodity importation into the requested PRA area is currently not authorized. 

 The commodity is currently permitted into a portion of the United States, but requestor wishes to expand the market 

(importing area).

 The commodity is currently permitted from a portion of the exporting country, but requestor wishes to expand the 

exporting area.

 Importation of the commodity with additional plant parts is requested. 

 The pest risk associated with the commodity has changed or is expected to change. For example:

 New mitigation measures for the commodity are proposed or implemented (e.g., irradiation)

 There is reason to believe (based on scientific studies or port-of-entry interceptions) that a new pest associated 

with the commodity has become established in the exporting area.

 New information indicates that a pest is likely to be more damaging in the PRA area than originally determined.

Continue to Process 2: Determining if a weed risk assessment for the commodity is needed on page 2-4.
Conducting Pest Risk Assesment in PPQ

Process 2: Determining if a weed risk assessment for the commodity is needed

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-4

Process 2: Determining if a weed risk assessment for the commodity is needed

In some cases, the imported commodity may have the potential to propagate 

and become invasive in the PRA area. The likelihood that this may happen is 

evaluated in a weed risk assessment, conducted separately from the commodity 

pathway risk assessment. A weed risk assessment need only be conducted 

under certain conditions. The project lead of the commodity pathway risk 

assessment is responsible for determining whether or not a weed risk 

assessment may be required and referring the plant for further analysis.

Procedure 2-1. Determining if a weed risk assessment for the commodity is 

needed

Follow steps 1-4 to determine whether a weed risk assessment is necessary. Because not all plant parts of 

every commodity are capable of propagation, consider not only the species proposed for import, but also the 

form in which the commodity will be imported. 

IF THEN

Step 1 The commodity is already 

enterable into the PRA 

area from other countries.

A weed risk assessment is not needed. In the “Determination of 

the necessity of a weed risk assessment for the commodity” section 

of the risk assessment, state that an assessment of weed risk potential is not required because the commodity is already enterable from 

other countries. Provide references. Continue to Process 3: Defining 

the pathway on page 2-6.

The commodity is not 

enterable into the PRA 

area from other countries.

Go to Step 2.

Step 2 The plant species is widely 

established (native or naturalized) in the PRA area. 

(If questionable, consult the 

weed team.)

A weed risk assessment is not needed. In the “Determination of 

the necessity of a weed risk assessment for the commodity” section 

of the risk assessment, state that an assessment of weed risk potential is not required because the commodity is already widely established in the PRA area. Provide references. Continue to Process 3: 

Defining the pathway on page 2-6.

The plant species is not 

widely established (native 

or naturalized) in the PRA 

area. (If questionable, consult the weed team.)

Go to Step 3.

Step 3 Any part of the imported 

commodity can easily 

propagate or be propagated.

Go to Step 4.

The imported commodity 

cannot easily propagate

or be propagated.

A weed risk assessment is not needed. In the “Determination of 

the necessity of a weed risk assessment for the commodity” section 

of the risk assessment, state that an assessment of weed risk potential is not required because the plant parts to be imported cannot be 

propagated. Provide references. Continue to Process 3: Defining 

the pathway on page 2-6.
Conducting Pest Risk Assesment in PPQ

Process 2: Determining if a weed risk assessment for the commodity is needed

2-5 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Step 4 A weed risk assessment 

has already been completed for this species.

A weed risk assessment is not needed. In the “Determination of 

the necessity of a weed risk assessment for the commodity” section 

of the risk assessment, state that an assessment of weed risk potential has already been completed. State the conclusions of the 

assessment and provide references. Continue to Process 3: Defining the pathway on page 2-6.

A weed risk assessment 

has not already been 

completed for this species.

A weed risk assessment may be required. Notify the weed team 

and in the “Determination of the necessity of a weed risk assessment for the commodity” section of the risk assessment, state 

“Because the commodity has the potential to be propagated, an 

assessment of weed potential may be required before importation of 

the commodity plant species is authorized. If required, the weed 

potential will be analyzed separately and will not be included in this 

document.” Continue to Process 3: Defining the pathway on page 

2-6.

Procedure 2-1. Determining if a weed risk assessment for the commodity is 

needed

Follow steps 1-4 to determine whether a weed risk assessment is necessary. Because not all plant parts of 

every commodity are capable of propagation, consider not only the species proposed for import, but also the 

form in which the commodity will be imported. 

IF THEN
Conducting Pest Risk Assesment in PPQ

Process 3: Defining the pathway

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-6

Process 3: Defining the pathway

The IPPC (2012) defines a pathway as “any means that allows the entry or 

spread of a pest.” In the context of commodity pest risk assessments, the 

pathway is the commodity to be imported, together with all the processes it 

undergoes from production to importation and distribution in the PRA area that 

may have an impact on pest risk. 

A detailed description of the pathway, including the morphological and 

physiological characteristics of the commodity, provides the necessary 

foundation for the risk assessment. 

NOTE

All components of the pathway, as they are described in the risk assessment, 

become mandatory conditions for importation of the commodity. Therefore, the pathway description should ultimately only include those components of the pathway that 

will actually be used the risk assessment as a basis for identifying the potential pests 

associated with the commodity and evaluating their risk.
Conducting Pest Risk Assesment in PPQ

Process 3: Defining the pathway

2-7 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Procedure 3-1. Defining the pathway

Based on the scope of the risk assessment, provide a detailed description of the pathway that includes the 

information listed in this procedure. All components of the pathway used in the risk assessment as a basis for 

evaluating pest risk become mandatory conditions for importation of the commodity.

The commodity to be imported, including

 plant part(s) to be imported (e.g., root, fruit, leaf) and inclusion/exclusion of specific other plant parts (e.g., stems, 

calyces, husks).

 condition at the time of entry (e.g., fresh, dried, processed).

 cultivar, variety, race, colors, variability, grade, size, restrictions (e.g., kosher), or other pertinent information.

 expected end-use (e.g., consumption, milling, etc.).

 stage of maturity at time of harvest.

 stage of maturity at time of import.

Production and harvest procedures in the exporting area that will be explicitly considered during the risk assessment. 

Examples include

 growing conditions (e.g., greenhouse, overhead irrigation).

 specific pest control or exclusion practices such as area freedom, biological control, pheromone disruption, routine 

pesticide application (including target pests of the treatments).

 planted crop (e.g., clean stock, host-resistance). If the planted crop is to be from certified seed or nursery stock, indicate the origin of the stock or seed (country, state).

 cultural practices such as sanitation, planting date, harvest timing, crop rotation, etc.

 method of harvesting (e.g., manual, clipped, machine-harvested, selective harvesting).

Post-harvest procedures in the exporting area that will be explicitly considered during the assessment. Examples 

include

 processing procedures such as chipping, washing, brushing, waxing, sieves.

 quality procedures such as culling, quality inspections.

 pest exclusion practices such as enclosures, screens.

 treatments (including target pests) such as dips, cold treatment/refrigeration, fumigation, irradiation, fungicide applications, hot water vapor treatments. 

 packing, boxing, and wrapping methods including special enclosures/protections, packaging, etc.

Shipping and storage conditions that will be explicitly considered during the assessment. Examples include

 storage duration and conditions (e.g., cold storage, modified humidity).

 shipping methods (e.g., truck, cargo).

 transit time. 

 timing of consignments (season).

A visual depiction of the pathway. Figure 2-1 provides a generic depiction, but the specific details and the level of detail 

will vary from case to case. 

Continue to Process 4: Creating the pest list and pest categorization on page 2-9.
Conducting Pest Risk Assesment in PPQ

Process 3: Defining the pathway

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-8

Figure 2-1. A generic graphic representation of a commodity pathway.
Conducting Pest Risk Assesment in PPQ

Process 4: Creating the pest list and pest categorization

2-9 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Process 4: Creating the pest list and pest categorization

In this process, we identify the plant pests that could become established in the 

PRA area as a result of the importation of the commodity and determine which 

of these pests meet the criteria for further analysis. The pests selected for 

further analysis are those whose association with the commodity pose a 

specific hazard to the PRA area because they are of regulatory significance and 

have a reasonable likelihood of being associated with the harvested 

commodity. 

Identifying pests for the pest list 

The process begins when we develop a list of pests in the export area that are 

known to be associated with the commodity anywhere in the world and to be of 

regulatory significance to the PRA area. Pests are considered to be of 

regulatory significance if they are “actionable” at U.S. ports of entry. 

Actionable pests include quarantine pests, regulated non-quarantine pests, 

pests considered for or under official control, and pests that require evaluation 

for regulatory action. Refer to National legislative framework for PRA on page 

1-14 for more details regarding national policies determining pest status for the 

purpose of pest listing in the risk assessment. Non-actionable pests that are 

present in the exporting area and known to be associated with the commodity 

are not placed on the pest list. Instead, these pests are recorded in a separate 

table along with supporting evidence in an appendix to the risk assessment. 

In general, we do not include pests on the pest list if the only evidence of 

presence in the exporting area is weak or dubious (e.g., very few interceptions 

in permit cargo, only interceptions in baggage from the exporting country, 

other evidence refutes any reports of pest presence in the host country). We list 

any pests with a doubtful distribution in the export area before the pest list in 

the “Pests considered but not included on the pest list” section. 

Similarly, we only list pests for which the commodity is a Type 1 host (natural 

host) or Type 2 host (conditional host) (refer to Supplement 3: Host Status on 

page 3-10 for an explanation of host types). If the evidence of host association 

is insufficient to conclude that the commodity is a Type 1 or Type 2 host, we do 

not list such pests. Instead, we list them in the “Pests considered but not 

included on the pest list” section. If there is evidence of a non-actionable 

vector in the exporting area that transmits an actionable pest, we list the 

actionable pest in the pest list and analyze it if appropriate; if we determine the 

actionable pest is a candidate for risk management, relevant information about 

the vector is included in the risk mitigation notes. Type 4 hosts (fomites) are 

included on the list if there is clear evidence that the commodity is a common 

pathway for the movement of the pest.

In general, we do not include organisms identified only to the genus level in 

the pest list, as the taxonomic unit for pests selected for evaluation beyond the 
Conducting Pest Risk Assesment in PPQ

Process 4: Creating the pest list and pest categorization

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-10

pest categorization stage is usually the species (ISPM No. 11: IPPC, 2004b). 

Instead, we list pests identified only to the genus level in the “Pests considered 

but not included on the pest list” section, and we prepare genus-level 

datasheets for those that have actionable regulatory status and have a 

reasonable likelihood of being associated with the harvested commodity.

Developing the pest list and selecting pests for further analysis

Pest categorization continues by determining which of the pests identified as 

actionable have a reasonable likelihood of being associated with the harvested 

commodity. Pests that are associated with the specific plant part(s) to be 

imported and are likely to remain viable with the plant part(s) throughout the 

harvesting process are generally considered to have a reasonable likelihood of 

being associated with the harvested commodity. These pests are analyzed 

further in Process 7: Assessing the likelihood of introduction on page 2-35 and/

or Process 8: Assessing potential consequences of introduction on page 2-50. 

Some plant pests may be of concern but are not selected for further analysis for 

a variety of reasons, such as

The pest is not associated with the harvested plant part(s) or is associated 

with those parts at an earlier stage but not at harvest.

The pest is mobile and will be eliminated while commodity is harvested.

The commodity is a conditional host, and there is high certainty the 

conditions for non-host status are met, etc.

If no actionable pests are likely to be associated with the harvested commodity, 

the risk assessment stops here.

Organisms identified only to the genus level

Organisms identified only to the genus level are difficult to assess, because 

pertinent biological information (pest status, hosts, distribution, behavior) 

usually differs sufficiently between species that a general conclusion for the 

genus is not possible. Also, if the genus in question is reported in the PRA area, 

we often cannot know if the unidentified species occurs in the PRA area and, 

consequently, whether or not it has actionable regulatory status for the PRA 

area. We therefore usually do not include organisms identified only to the 

genus level on the pest list, and we do not assess them using Process 7: 

Assessing the likelihood of introduction or Process 8: Assessing potential 

consequences of introduction. 

However, because genus-level organisms may still pose a risk to the PRA area, 

it is not justifiable to simply ignore them. Instead, we usually address them by 

following Procedure 4-5: Handling organisms identified only to genus level. 

According to this procedure, unless there is a PPQ policy decision to the 

contrary, if the genus is not present in the PRA area, the U.S. regulatory status 
Conducting Pest Risk Assesment in PPQ

Process 4: Creating the pest list and pest categorization

2-11 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

of the “Genus sp.” organism is “actionable,” whereas if the genus is present in 

the PRA area, the status is either “non-actionable” or “undetermined.” For any 

“Genus sp.” organisms with actionable regulatory status that could be on the 

harvested commodity plant part(s), we prepare a genus-level datasheet to be 

used by risk managers as a basis for determining if measures beyond those 

intended to mitigate fully identified pests are warranted. Often, however, the 

development of detailed assessments for known pests that inhabit a variety of 

ecological niches, such as internal fruit feeders or foliage pests, allows 

effective mitigation measures to eliminate the known organisms as well as 

similar but incompletely identified organisms that inhabit the same niche.

It is important to note that there may be situations when it is appropriate not to 

follow Procedure 4-5: Handling organisms identified only to genus level. In 

particular, if there is sound evidence that the species in question (though 

identified only to genus) is different from any species of that genus known to 

occur in the PRA area (e.g., broader areas of establishment or host range), it 

should be listed as an “actionable” pest. Also, there may be situations when a 

full analysis using Process 7: Assessing the likelihood of introduction and/or 

Process 8: Assessing potential consequences of introduction, instead of a 

genus-level datasheet, is warranted, such as when there is sufficient biological 

information on the unidentified organism to allow for proper analysis of its 

likelihood and consequences of introduction. If a full analysis is prepared, the 

pest should be included on the pest list. 

Procedure 4-1. Identifying potential pests for the pest list

Follow steps 1-6 to identify potential pests for the pest list.

Step 1 Identify pests associated with the commodity plant anywhere in the world. In this case, “association” 

includes any instance where you have evidence that links a pest to the commodity. Note that the 

actual host status (or strength of the association) will be evaluated in a subsequent procedure. Go 

to Step 2.

Step 2 Determine whether the pests identified in Step 1 are found in the exporting area. Go to Step 3.

Step 3 For organisms identified only to the genus level, go to Procedure 4-5: Handling organisms identified 

only to genus level.

For organisms identified to the species level or lower (e.g., biotypes, strains, race), go to Step 4.
Conducting Pest Risk Assesment in PPQ

Process 4: Creating the pest list and pest categorization

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-12

Procedure 4-2. Optional: Determining whether a pest is actionable

This procedure applies to pests identified to the species level or lower. For 

organisms identified only to the genus level, continue to Procedure 4-5: 

Handling organisms identified only to genus level. This procedure is 

applicable for most pests, but in some cases, you may need to consult other 

sources to determine whether a pest is actionable. It is not necessary, or in 

some cases appropriate, to use this procedure in instances where the PPQ 

policy for the pest is already known (e.g., armored scales, which are nonreportable on commodities for consumption; some citrus pathogens where fruit 

is not a pathway for introduction, etc.). Treat pests listed as “reportable” in 

PestID as actionable, unless a specific note in PestID or other PPQ port policy 

indicates otherwise. It also may be useful to consult previous PRAs in which 

the pest is listed, check domestic Emergency Action Notifications (EANs) for 

any evidence of domestic regulation, or seek information from DEEP 

(Deregulation Evaluation for Established Pests) or NPAG (New Pest Advisory 

Group) to clarify pest status.

Step 4 Determine whether each pest is actionable at U.S. ports of entry on commodities for consumption. 

Actionable pests include quarantine pests, regulated non-quarantine pests, pests considered for or 

under official control, and pests that require evaluation for regulatory action. Go to Step 5.

Procedure 4-2: Optional: Determining whether a pest is actionable may be useful in determining 

whether a pest is actionable, but in some cases, you may need to consult other sources to make a 

determination. 

Step 5 Place pests with a non-actionable regulatory status in a separate table in an appendix to the risk 

assessment (PRA Template: Appendix A). You should provide supporting references in this appendix, including PPQ policy on non-actionable status, if relevant. See the PRA Template for more 

details.

For actionable pests associated with the commodity and found in the export area, go to 

Procedure 4-3: Determining whether to include an actionable pest on the list.

Procedure 4-1. Identifying potential pests for the pest list

Follow steps 1-6 to identify potential pests for the pest list.

Follow the steps of this procedure to determine whether a pest is actionable. 

IF THEN

Step 1 The pest’s genus is listed in PestID. Go to Step 2.

The pest’s genus is not listed in PestID. Go to Step 6.

Step 2 The entire genus (i.e., “Genus spp.”) is listed as 

“non-reportable.”

The pest is non-actionable. Refer back to Step 5

of Procedure 4-1: Identifying potential pests for the 

pest list.

The entire genus (i.e., “Genus spp.”) is not listed

as “non-reportable.”

Go to Step 3.
Conducting Pest Risk Assesment in PPQ

Process 4: Creating the pest list and pest categorization

2-13 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Step 3 The pest species (or sub-species, if applicable) is 

listed in PestID.

Go to Step 4.

The pest species (or sub-species, if applicable) is 

not listed in PestID.

Go to Step 6.

Step 4 The pest is listed as “non-reportable” (either for all 

commodities or for commodities for consumption).

The pest is non-actionable. Refer back to Step 5

of Procedure 4-1: Identifying potential pests for the 

pest list.

The pest is not listed as “non-reportable.” Go to Step 5.

Step 5 The pest is listed as “reportable” (either for all commodities or for commodities for consumption).Assume the pest is actionable. Continue to 

Procedure 4-3: Determining whether to include an 

actionable pest on the list.

The pest is not listed as “reportable.” Seek further guidance from National Identification 

Services or another regulatory expert.

Step 6 There is evidence that the pest is present in the 

PRA area.

Go to Step 7.

There is no evidence that the pest is present in 

the PRA area.

Assume the pest is actionable. Continue to 

Procedure 4-3: Determining whether to include an 

actionable pest on the list.

Step 7 There is a PPQ program or restriction policy in 

place for the pest--for example, the pest is under 

PPQ official control.

Assume the pest is actionable. Continue to 

Procedure 4-3: Determining whether to include an 

actionable pest on the list.

There is not a PPQ program or restriction policy

in place for the pest.

Assume the pest is non-actionable. Refer back to 

Step 5 of Procedure 4-1: Identifying potential pests 

for the pest list.

Follow the steps of this procedure to determine whether a pest is actionable. 

IF THEN

Procedure 4-3. Determining whether to include an actionable pest on the list

Follow the steps of this procedure to determine whether to include an actionable pest on the list.

IF THEN

Step 1 The available evidence indicates that the pest is 

associated with the commodity plant species (anywhere in the world).

Go to Step 2.

The available evidence does not indicate that the 

pest is associated with the commodity.

Do not include the pest on the pest list. Explain 

your rationale in the “Pests considered but not 

included on the pest list” section of the risk assessment.

Step 2 The available evidence indicates the pest occurs

in the export area.

Go to Step 3.

The available evidence does not indicate the pest 

occurs in the export area.

Do not include the pest on the pest list. Explain 

your rationale in the “Pests considered but not 

included on the pest list” section of the risk assessment.
Conducting Pest Risk Assesment in PPQ

Process 4: Creating the pest list and pest categorization

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-14

Step 3 The commodity plant species is a Type 1 host (natural host) for the pest, based on the pest’s association with the host species in any country of the 

world.

Include the pest on the pest list. Continue to 

Procedure 4-4: Completing the pest list table.

The commodity plant species is a Type 2 host 

(conditional host) for the pest, based on the pest’s 

association with the host species in any country of 

the world.

Include the pest on the pest list. Continue to 

Procedure 4-4: Completing the pest list table.

The commodity plant species is a Type 3 host (natural non-host) for the pest, based on the pest’s 

association with the host species in any country of 

the world.

Do not include the pest on the pest list. Explain 

your rationale in the “Pests considered but not 

included on the pest list” section of the risk assessment.

The commodity plant species is a Type 4 host 

(fomite) for the pest, based on the pest’s association with the host species in any country of the 

world.

Include the pest on the pest list if there is clear 

evidence that the commodity is a common pathway for movement of the pest. Explain your rationale in the “Remarks” section of the pest list or in 

the “Notes on pests identified in the pest list” section. Continue to Procedure 4-4: Completing the 

pest list table.

Otherwise, do not include the pest on the pest 

list. Explain your rationale in the “Pests considered 

but not included on the pest list” section of the risk 

assessment.

Procedure 4-3. Determining whether to include an actionable pest on the list

Follow the steps of this procedure to determine whether to include an actionable pest on the list.

IF THEN
Conducting Pest Risk Assesment in PPQ

Process 4: Creating the pest list and pest categorization

2-15 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Procedure 4-4. Completing the pest list table

For each step in this procedure, document supporting information in the pest 

list or in the body of the risk assessment. Where applicable, indicate sources of 

uncertainty, but do not use uncertainty codes. Be specific and clearly link 

appropriate evidence to relevant citation(s). If you have text that is too long to 

reasonably fit in this pest list table, put this text in section 2.3 “Notes on pests 

identified in the pest list” of the PRA Template and state in the pest list table 

“see additional discussion below in section 2.3.”

The pest list should be presented using the format shown in Table 2-1. 

Arthropods should be listed alphabetically by order and then family. Pathogens 

should be divided by type. They should be listed after the arthropods and 

proceed as follows: 1) Nematodes, 2) Fungi and Chromistans, 3) Bacteria and 

Phytoplasmas, 4) Viruses and Viroids, and 5) Pathogens of Unknown Etiology 

(biotic factors only). Other non-traditional entries, such as algae or protozoans, 

are to be listed in categories of their own as well. Pathogens should be listed 

alphabetically under each type (“type” meaning: nematodes, etc.). 

Organization like the arthropods (separated by order and family) is not an 

efficient or stable way to present the pathogens due to the continuous revisions 

in pathogen taxonomy. These revisions are based on new evidence, and, with 

the growing application of molecular tools for identification, additional 

revisions are anticipated.

Follow the steps of this procedure to complete the pest list table.

Step 1 Fill out each column on the pest list as follows, then go to Step 2.

Pest name:

 List the current scientific name of the pest, including the authority. 

 List valid synonyms if needed to support information provided in the pest list. 

 In some cases, it might be appropriate to identify the organism below the species level (e.g., 

biotypes, race, or strains); consult the appropriate authority for guidance. If listing an organism 

below the species level, clearly document the rationale for doing so. The rationale “should 

include evidence demonstrating that factors such as differences in virulence, host range or vector relationships are significant enough to affect phytosanitary status” (ISPM No. 11: IPPC, 

2004b).

 If only a common name is known, list it as such and incorporate the uncertainty level associated 

with a common name.

Evidence of presence in export area:

 Identify the evidence that the pest is found in the export area.

 Describe uncertainty regarding distribution and, if relevant, regulatory status in the exporting 

country (e.g., limited distribution and under official control).
Conducting Pest Risk Assesment in PPQ

Process 4: Creating the pest list and pest categorization

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-16

Host status:

 State the host status of the commodity plant species for the pest (see Supplement 3: Host Status on page 3-10). 

 Base your conclusions on evidence of the pest’s association with the imported plant species in 

any country of the world.

 If the commodity plant species is a Type 2 (conditional) host for the pest, provide information on 

the specific conditions under which it is a host and provide an explanation of the evidence and 

your uncertainty. If strong evidence indicates the commodity is a Type 2b host (i.e., non-host), 

still include the pest on the pest list, and include information regarding non-host status under 

“On harvested plant part(s)?”. 

 If the commodity is a Type 4 host (fomite), provide evidence that the commodity is a common 

pathway for movement of the pest.

Plant part(s) association:

 Identify the part or parts of the plant with which the pest is physically associated. Ideally, evidence should refer to the actual plant species to be imported and the actual pest species under 

analysis. However, in some cases, we may extrapolate from evidence referring to other plant 

species or closely related pest species. In these cases, provide information on your logic, 

assumptions for extrapolation, and uncertainty.

On harvested plant part(s)?:

 Indicate if the pest has a reasonable likelihood of being on and remaining with the plant part(s), 

in viable form, throughout the harvesting process. Consider all plant parts present after harvest 

but prior to post-harvest processing. Do not consider post-harvest practices, such as washing, 

dipping, etc., at this step even when they are routine. 

 Answer “Yes” or “No” and, if appropriate, cite and/or discuss evidence for your decision. Note: 

“Yes” indicates simply that the pest has a reasonable likelihood of being associated with the harvested commodity; the level of pest prevalence on the harvested commodity (low, medium, or 

high) is qualitatively assessed in Risk Element A1: Pest prevalence on the harvested plant 

part(s) as part of Process 7: Assessing the likelihood of introduction.

 Answer yes if:

 The commodity plant species is a Type 1 host (natural host) for the pest, and the pest 

is reasonably likely to be associated with the commodity plant part(s) to be imported 

following harvesting from the field and prior to any post-harvest processing. 

 The commodity plant species is a Type 2 host (conditional host) for the pest, and 

conditions in the exporting area are such that there is a reasonable likelihood that 

the pest will be associated with the commodity plant part(s) to be imported following 

harvesting from the field and prior to any post-harvest processing. 

 Answer no if:

 Characteristics of the pest, commodity, or harvesting process are such that it is 

unlikely the pest will be on the commodity after it is harvested.

 The commodity plant species is a Type 2 host (conditional host) for the pest, and 

there is a reasonably high level of certainty that the conditions for non-host status 

(Type 2b host) are met (e.g., specific varieties used for export known to be a nonhost, specific timing of harvest, only evidence of host association under experimental conditions), and the status is supported by sufficient evidence. Keep the pest in 

the pest list table, and explain the conditions and evidence for the Type 2b status. 

Those pests for which the answer was yes, continue to Process 5: Collecting information and defining the endangered area on page 2-22. 

If there are no pests for which the answer is yes, the risk assessment stops here.

Follow the steps of this procedure to complete the pest list table.
Conducting Pest Risk Assesment in PPQ

Process 4: Creating the pest list and pest categorization

2-17 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Remarks:

Use this section for information pertinent to the pest list, but that does not fall under the previous 

columns. For example: 

 For pests that have a limited distribution in the United States but are included on the pest list 

because they are actionable pests: list the pest’s distribution in the PRA area and provide references, including PestID or agency correspondence.

 Overarching assumptions and/or uncertainty.

Step 2 Summarize the following information in sub-sections placed after the pest list table in the risk 

assessment:

 “Notes on pests identified in the pest list”: Summarize information that is too lengthy to fit in the 

main pest list table. This sub-section can also include a summary of actionable pests not 

selected for further analysis, including the justification for why they were not selected (e.g., the 

organism is not likely to be associated with the harvested plant part(s), the commodity meets 

the criteria for a Type 2b host for a pest, existing PPQ policy does not require analysis of those 

pests).

 “Pests selected for further analysis”: List those pests on the pest list for which the answer to “On 

harvested plant part(s)?” is “Yes”. 

If you have completed your pest list, continue to Process 5: Collecting information and defining the endangered 

area on page 2-22.

Follow the steps of this procedure to complete the pest list table.

Table 2-1. Actionable pests reported on [species name of plant to be imported] (in any country) and present in 

[export area] (on any host).

Pest name Evidence of presence in the export 

area

Host status Plant part(s) 

association

On the harvested plant 

part(s)?

Remarks

Genus species 

Authority

REF

Describe any uncertainty regarding distribution and, if 

relevant, regulatory 

status in the exporting country (REF)

Type 1, 2, or 4 

(REF)

If applicable, 

provide brief 

justification for 

judgments and 

conclusions 

(REF)

For Type 4 

hosts, provide 

additional justification for 

inclusion on 

pest list (REF)

Indicate the 

part(s) of the 

plant with 

which the pest 

is associated 

(i.e., fruit, flowers, stems, 

leaves, roots). 

Consider association on the 

actual imported 

plant species

Describe 

uncertainty 

regarding plant 

part association including 

any extrapolations or 

assumptions 

(REF)

Yes or No

Provide brief 

justification for 

judgments and 

conclusions 

(REF)

If pest is present in the 

United States:

“Present in [List 

States]” (REF)

Optional:

Include a brief 

explanation of 

any additional 

information you 

feel is necessary to capture 

in the pest list
Conducting Pest Risk Assesment in PPQ

Process 4: Creating the pest list and pest categorization

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-18

Procedure 4-5. Handling organisms identified only to genus level

Refer to the following notes when completing this procedure.

Note 1. An organism identified to the genus level should only be included 

in the risk assessment if it is reported simultaneously on the commodity 

and in the export area in the same reference [e.g., “Genus sp. attacks 

Commodity X in Country X (Anonymous, 2010)”].

Note 2. Treat pests listed as “reportable” in PestID as “actionable,” unless 

a specific note in PestID or other PPQ port policy indicates otherwise.

Note 3. There may be situations when it is appropriate not to follow this 

procedure (see Organisms identified only to the genus level on page 

2-10). If this is the case, clearly document the evidence and associated 

uncertainty for this decision in the risk assessment.

Follow the steps in this procedure to determine how to handle organisms identified only to genus level.

IF THEN

Step 1 The genus (i.e., “Genus sp.”) is 

listed in PestID.

Go to Step 2.

The genus (i.e., “Genus sp.”) is 

not listed in PestID.

Go to Step 3.

Step 2 The whole genus (i.e., “Genus

sp.”) is listed as “reportable” in 

PestID in the PRA area.

The pest either has actionable or undetermined regulatory status. Go to Step 3.

The whole genus (i.e., “Genus

sp.”) is listed as “non-reportable” in PestID in the PRA 

area.

The pest is non-actionable. Refer back to Step 5 of 

Procedure 4-1: Identifying potential pests for the pest list.

Step 3 There is adequate evidence 

that the pest occurs on the 

commodity in the export area.

Add the pest to Table 1 in the “Organisms identified only to genus 

level” section of the risk assessment. Go to Step 4.

There is not adequate evidence that the pest occurs on 

the commodity in the export 

area.

Add the pest to the “Pests with weak evidence for association with 

the commodity or for presence in the export area” section of the risk 

assessment.

Step 4 Any species in the genus is 

present in the PRA area.

In Table 1 of the “Organisms identified only to genus level” section 

of the risk assessment, indicate that the genus is present in the 

PRA area and that the regulatory status is undetermined. Go to 

Step 5.

The genus is not present in 

the PRA area.

In Table 1 of the “Organisms identified only to genus level” section 

of the risk assessment, indicate that the genus is not present in the 

PRA area and that the regulatory status is actionable. Go to Step 5.

Step 5 The pest could be associated

with the harvested commodity 

plant parts.

In Table 1 of the “Organisms identified only to genus level” section 

of the risk assessment, indicate that the pest could be associated 

the harvested plant parts. Go to Step 6.
Conducting Pest Risk Assesment in PPQ

Process 4: Creating the pest list and pest categorization

2-19 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

The pest could not be associated with the harvested commodity plant parts.In Table 1 of the “Organisms identified only to genus level” section 

of the risk assessment, indicate that the pest could not be associated with the harvested plant parts.

Step 6 The pest has undetermined 

regulatory status.

In the risk mitigation notes document, state that the level of risk of 

the congeners (if any are to be analyzed in the risk assessment) 

may or may not be similar to that of the organism in question, and 

that in general, there is high uncertainty regarding efficacy of risk 

mitigation measures when applied to organisms identified only to 

the genus level.

The pest has actionable status.For each pest, create a genus-level datasheet. (Note: Do not create 

a datasheet for pests with undetermined regulatory status). The 

datasheet should include the following primary elements: 

 absence of the genus in the PRA area and regulatory status of 

some species belonging to it (if information is available).

 distribution of species from the genus in the world and potential 

for establishment in PRA area.

 known host range (plant species and families) of different species within this genus.

 biology contributing to dispersal (fecundity, number of generations, ability for active dispersal on its own or through human 

activities) and possibility of spread in PRA area.

 potential for economic and environmental consequences in the 

PRA area. The following factors should be considered when 

assessing significance of the genus.

 previous history of successful establishment in new areas. 

 phytopathogenic or phytophagous characteristics. 

 observations of causing injury to plants, beneficial organisms, 

etc.

 being reported as pests.

 ability to act as a vector for known pests.

 adverse effects on non-target organisms beneficial to plants 

(such as pollinators or predators of plant pests). 

 interception records.

Include the genus level datasheet as an appendix to the main risk 

assessment document. Summarize the information from the datasheet after Table 1 in section 2.1.3. “Organisms identified only to the 

genus level” of the risk assessment.

In the risk mitigation notes document, state that the level of risk of 

the congeners (if any are analyzed in the risk assessment) may or 

may not be similar to that of the organism in question, and that in 

general there is high uncertainty regarding efficacy of risk mitigation 

measures when applied to organisms identified only to the genus 

level.

Continue to Process 5: Collecting information and defining the endangered area on page 2-22.

Follow the steps in this procedure to determine how to handle organisms identified only to genus level.

IF THEN
Conducting Pest Risk Assesment in PPQ

Processes in PPQ commodity import risk assessment

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-20

Stage 2: Pest Risk Assessment

Stage 2 of pest risk analysis is composed of two distinct phases: pest 

categorization and risk assessment. In PPQ commodity import risk 

assessments, the first phase, pest categorization, begins as the pest list is built 

in Process 4: Creating the pest list and pest categorization and continues in 

Process 5: Collecting information and defining the endangered area when we 

define the area endangered by the pest. The second phase, risk assessment, is 

the heart of Stage 2 and involves analyzing biological and economic 

information about the pests selected for further analysis in order to estimate 

their likelihood of being introduced into the PRA area (via the commodity) and 

identifying the potential economic and environmental impacts that would 

result from their introduction. 

Processes in PPQ commodity import risk assessment

In PPQ, pest risk assessment is divided into five processes:

Process 5: Collecting information and defining the endangered area

Process 6: Assessing uncertainty for risk elements

Process 7: Assessing the likelihood of introduction

Process 8: Assessing potential consequences of introduction

Process 9: Summarizing the final risk ratings and uncertainty

Risk elements evaluated in PPQ commodity import risk assessment

The likelihood that a pest will be introduced into the PRA area via the 

commodity is analyzed in Process 7: Assessing the likelihood of introduction. 

By definition (ISPM No. 5: IPPC, 2012), this likelihood includes both the 

likelihood of the pest entry in the PRA area and the likelihood of its 

establishment in the PRA area upon entry. We determine the likelihood of 

introduction by evaluating the following risk elements (described in detail in 

Process 7).

NOTE

Pest risk assessment is not linear; although the processes of Stage 2 are numbered 

and described individually for convenience, they are not necessarily completed 

sequentially. Each process provides the framework and specific instructions for conducting various individual aspects of commodity import risk assessment, but analysts have flexibility in approaching each process and determining the best order in 

which to complete the assessment.
Conducting Pest Risk Assesment in PPQ

Risk elements evaluated in PPQ commodity import risk assessment

2-21 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

The potential impacts of a pest introduction in the PRA area are evaluated in 

Process 8: Assessing potential consequences of introduction. Once a pest has 

entered the PRA area, it must be able to establish and subsequently spread in 

order for there to be consequences. The consequences of introduction are 

determined by evaluating the following risk elements (described in detail in 

Process 8). 

Risk Element A: Likelihood of entry

 Risk Element A1: Pest prevalence on the harvested plant part(s)

 Risk Element A2: Likelihood of surviving post-harvest processing before shipment

 Risk Element A3: Likelihood of surviving transport and storage conditions of the consignment

Determining the likelihood of establishment (Risk Element B)

 Risk Element B1: Likelihood of coming into contact with host material in the endangered 

area

 Risk Element B2: Likelihood of arriving in the endangered area

Risk Element C: Determining the potential direct impacts

 Risk Element C1: Damage potential in the endangered area

 Risk Element C2: Spread potential

Risk Element D: Determining potential trade impacts

 Risk Element D1: Determining export markets at risk

 Risk Element D2: Likelihood of trading partners imposing additional phytosantiary 

requirements

NOTE

We evaluate spread potential as a part of the potential consequences of introduction 

because it relates to how quickly the pest will be able to cause full impacts in the 

PRA area. 
Conducting Pest Risk Assesment in PPQ

Process 5: Collecting information and defining the endangered area

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-22

Process 5: Collecting information and defining the endangered area

The purpose of this process is to gather and organize the biological, 

environmental, and economic information necessary for evaluating each of the 

risk elements and to determine the logical order in which they should be 

evaluated. Before beginning this process, analysts should first determine 

whether an assessment or other standard text (e.g., Pest Notes) has already 

been developed for the pest that could be relevant for the commodity pathway 

being assessed. 

In general, assessment of the likelihood of entry involves evaluating the 

biology of the pest in terms of how the pest relates to the conditions of the 

pathway and the characteristics of the commodity that were described in 

Process 3: Defining the pathway. Assessing the likelihood of establishment, 

spread, and the subsequent potential impacts of the pest in the PRA area 

involves evaluating the biology of the pest in relation to the suitability of 

conditions in the PRA area. Those conditions include biotic factors (e.g., 

availability of host material, presence or absence of natural enemies) and 

abiotic factors (e.g., temperature, season, humidity, rainfall, or other 

environmental conditions that affect the ability of the pest to survive and 

reproduce). 

Gathering information and identifying sources of uncertainty

The first part of Process 5 involves gathering the necessary information to 

complete Process 7: Assessing the likelihood of introduction and Process 8: 

Assessing potential consequences of introduction. Analysts can and should 

consult many different sources of information in this process, such as the 

scientific literature, databases, compendia, information provided by the 

exporting country, and subject matter experts. As much as possible, the 

information obtained should relate to the specific pest and how it behaves on 

hosts and in environmental conditions similar to those present the PRA area. 

When such information is unavailable, analysts may need to extrapolate from 

other related pests and situations. Analysts should explicitly note when 

collected data are based on extrapolations as it is an important factor in 

evaluating uncertainty. The type of information needed to complete Process 7: 

Assessing the likelihood of introduction and Process 8: Assessing potential 

consequences of introduction includes the following.

Information about the export area

 prevalence of a pest or disease agent in the exporting area

 geographic and environmental characteristics

 standard industry practices and procedures in the export area

 surveillance system(s)

 effectiveness of mitigation measures an treatments in the areas where (and if) controlled
Conducting Pest Risk Assesment in PPQ

Process 5: Collecting information and defining the endangered area

2-23 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

 previous risk assessments (including those of foreign countries) of the commodity and 

related commodities from the same origin

Information about the commodity

 type or class of commodity

 nature of raw material used to produce the commodity

 intended use of the product

 pest or disease agent survival in transit

 interception data

Pest-specific information

 potential host range of the pest in the PRA area

 symptoms expected to be caused by the pest on important potential hosts in the PRA 

area and plant parts affected

 type and degree of damage caused

 secondary damage that may occur as a result of the pest

 life history of the pest

 life stages (including duration)

 reproductive strategies (sexual, parthenogenetic, etc.)

 adaptive characteristics (dormancy, increased fecundity, number of generations, known 

expansion of host range, etc.)

 climatic/environmental constraints of the pest

 temperature/humidity requirements

 current geographic distribution

 ease of detection/inspection

 on commodity (e.g., size, ability to hide, signs of damage, latency, distinctiveness of 

symptoms)

 in the environment (e.g., methods of detection, including trapping mechanisms, signs of 

damage/presence)

 ease of identification

 similarity to other species

 methods of identification/diagnostics

 ease of identification of various life stages

 ease of removal of the pest from infested/infected commodity during standard packinghouse practices (e.g., washing, brushing, waxing)

 means of dispersal

 natural mobility of life stages (adult flight, larval silk ballooning, etc.)

 vectors (and presence of vectors in the PRA area)

 other mechanisms required for successful dispersal (wind, rain, soil, etc.)

 other requirements necessary for dispersal (e.g., the availability of a particular phenological stage of the host)

 prevention and control strategies used for the pest anywhere in the world

 field control

 phytosanitary measures

 possible effect of standard industry practices on survival of the pest
Conducting Pest Risk Assesment in PPQ

Process 5: Collecting information and defining the endangered area

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-24

In addition to considering the type of information available, analysts should be 

aware that the quality of the information will vary based on the source. Both 

the quality and applicability of available information will impact the certainty 

of the resulting risk rating. Supplement 4: Evaluation of Evidence on page 3-29

provides general guidance on how analysts can relate both the quality and 

applicability of evidence to their level of uncertainty (Process 6: Assessing 

uncertainty for risk elements on page 2-33). Analysts should identify gaps in 

knowledge and possible areas for future research in the mitigation notes 

(Process 10: Risk mitigation notes on page 2-67). 

When gathering information, analysts should keep in mind the scope of the 

analysis and the description of the pathway. In some cases it may be 

unnecessary to gather detailed information on the biology of the pest or on the 

environmental conditions in the PRA area, particularly when it is clear that the 

rating for a particular risk element is likely to be negligible. For example, if the 

scope of the analysis explicitly includes evaluating a post-harvest treatment 

such as irradiation or fumigation that will, with a high degree of certainty, 

remove the pest from the pathway (or render it inviable), the likelihood of 

entry of the pest will be negligible and it would be unnecessary to gather 

additional information about this pest. 

 existing export protocol requirements where host commodities are currently enterable

Information about the PRA area

 After clearly defining the PRA area for the particular risk assessment (e.g., continental 

United States, all 50 U.S. states, U.S. territories only), analysts should consider information regarding

 distribution of the commodity

 availability of susceptible hosts and/or competent vectors

 geography and environment

 control and production practices

 presence of similar pests
Conducting Pest Risk Assesment in PPQ

Process 5: Collecting information and defining the endangered area

2-25 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Determining the order of analysis

When the endangered area is defined and it is determined that at least some 

part of the PRA area could be endangered by the pest, an analyst should 

commence the risk assessment phase. As previously mentioned, Process 7: 

Assessing the likelihood of introduction and Process 8: Assessing potential 

consequences of introduction can be conducted in either order. If it is 

determined that the risk associated with either the likelihood or consequences 

of introduction is Negligible, it may be unnecessary to complete the other 

processes. Further, within Process 7, the analysis of the individual risk 

elements can be completed in any order. In other words, in most cases, an 

analyst can start an assessment with any one of the following procedures.

In deciding the best order to proceed with the assessment, analysts should first 

consider whether the risk ratings for one or more of the elements are likely to 

be negligible. An element that is likely to have a negligible risk rating should 

generally be evaluated first, in order to avoid needless research and analysis. 

Next, analysts should consider the availability, quality, and applicability of 

information necessary for evaluating each of the risk elements (see 

Supplement 4: Evaluation of Evidence on page 3-29). As a general principle, it 

is more efficient to first evaluate the risk elements for which there is the 

greatest amount of reliable evidence available. 

With experience, analysts will be able to decide which risk elements to 

evaluate first.

Defining the endangered area

While the PRA area is the area for which the risk assessment is intended, the 

endangered area is defined as the portion of the PRA area where ecological 

factors favor the establishment of the pest and where the presence of the pest 

will result in economically important losses. In some cases, the area 

endangered by the pest may be as large as the entire PRA area, but in other 

cases, when the pest is restricted by climate or hosts, the endangered area may 

only constitute a small portion of the PRA area.

There are two important parts to determining the endangered area. First we 

identify the portion of the PRA area where the organism is likely to be able to 

establish. Then, we determine whether the pest has the potential to damage 

economically important plants in that area. 

Procedure 7-1: Assessing the likelihood of entry (Risk Element A)

Procedure 7-2: Determining the likelihood of establishment (Risk Element B)

 Risk Element B1: Likelihood of coming into contact with host material in the endangered 

area OR

 Risk Element B2: Likelihood of arriving in the endangered area

Procedure 8-1: Determining the potential direct impacts (Risk Element C)
Conducting Pest Risk Assesment in PPQ

Process 5: Collecting information and defining the endangered area

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-26

Identifying the portion of the PRA area where the pest can actually survive and 

cause negative impacts is a crucial precursor to determining the potential risk 

of the pest in terms of its likelihood of establishment and associated 

consequences. Based on the biology of the pest and the identified biotic and 

abiotic conditions of the PRA area, analysts determine the area endangered by 

the pest (i.e., the endangered area) by identifying the portion of the PRA area 

where the pest can likely establish and cause economically important 

consequences. Important factors that influence where the organism can survive 

include abiotic factors such as temperatures (minimum/maximum), humidity, 

and rainfall, and biotic factors such as the availability of suitable host material. 

Host material suitable for survival might include uncultivated, unmanaged 

plants, or even weeds, that are not economically important. However, for the 

purposes of these Guidelines, we will be considering as pest hosts only 

economically important plants that occur in the areas of suitable climatic 

conditions. As a result, we assume that the area potentially suitable for a pest 

establishment is the same as the endangered area. 

In many cases, we do not have detailed information on the abiotic requirements 

of the pest or on the abiotic conditions of the PRA area. The global plant 

hardiness zone map developed by Magarey et al (2008) groups regions that 

have the same average annual extreme minimum temperature into distinct 

zones (Figure 2-2), allowing for easy comparison and matching of the 

temperature suitability in the areas of the pest’s current distribution elsewhere 

in the world to that of the PRA area. Because temperature, particularly low 

winter temperature, is often a critical factor determining the geographical 

range of many organisms (especially insects) (Worner, 1998; Bale et al., 2002), 

the area endangered by a pest can often be described in terms of average 

minimum temperature zones by “plant hardiness zone matching.” It is 

important to note that when we use this method to define the portion of the 

PRA area climatically suitable for pest establishment, we are making two 

implicit assumptions: 1) that cold tolerance is the major limiting factor of the 

pest’s current distribution, and 2) that cold tolerance is likely to be the major 

restriction in the PRA area. 

If analysts have specific information that can narrow this area or otherwise 

provide more precision, the endangered area may be described by other 

relevant means, so long as the boundaries (such as states or counties) are 

clearly identified (see Procedure 5-2: Defining the endangered area). In any 

case, regardless of how the endangered area of the pest is defined, it must have 

both a suitable climate and available hosts.
Conducting Pest Risk Assesment in PPQ

Process 5: Collecting information and defining the endangered area

2-27 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Figure 2-2. Temperature zones (aka “plant hardiness zones”) for defining the endangered area (Magarey et 

al., 2008).
Conducting Pest Risk Assesment in PPQ

Process 5: Collecting information and defining the endangered area

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-28

Procedure 5-1. Determining the order of analysis

Follow the steps below to determine the order of analysis.

IF THEN

Step 1 An analysis or other standard text has already 

been developed for the pest that is relevant for the 

commodity pathway being assessed. (Check Pest 

Notes and/or the PRA library.)

If appropriate, use the analysis in your assessment 

and continue to Process 9: Summarizing the final 

risk ratings and uncertainty on page 2-63.

Otherwise, go to Step 2.

No analysis or other standard text has developed

for the commodity pathway being assessed.

Go to Step 2.

Step 2 Based on the scoping call, the defined pathway 

explicitly includes treatments (such as irradiation 

or fumigation) that would likely lead to the pest having a negligible likelihood of entry.

Continue to Procedure 7-1: Assessing the likelihood 

of entry (Risk Element A).

Based on the scoping call, the defined pathway 

does not include any treatments (such as irradiation or fumigation) that would likely lead to the pest 

having a negligible likelihood of entry.

Go to Step 3.

Step 3 Conduct a preliminary search for information on the pest (see Gathering information and identifying sources 

of uncertainty). Consider the availability, quality, and applicability of information necessary for evaluating 

each of the risk elements and then determine your order of analysis. As a general principle, it is more efficient 

to first evaluate the risk elements for which there is the greatest amount of reliable evidence available.

In determining the order of analysis, keep in mind that the pest analysis can stop if: 

 The Likelihood of Entry is rated Negligible. 

 There is no endangered area (Procedure 5-2: Defining the endangered area). 

 The pest is determined to be a non-threshold pest (Process 8: Assessing potential consequences of 

introduction on page 2-50)

 Either Risk Element B1 or Risk Element B2 (under Likelihood of Establishment) is rated Negligible.
Conducting Pest Risk Assesment in PPQ

Process 5: Collecting information and defining the endangered area

2-29 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Procedure 5-2. Defining the endangered area

NOTE

This procedure is unnecessary when Risk Element A: Likelihood of entry is rated 

Negligible. It may also be unnecessary if the pest is highly unlikely to transfer from 

the commodity to a new host on its own (see Step 1 of Risk Element B1: Likelihood 

of coming into contact with host material in the endangered area).

Determine the area endangered by the pest by following the steps in this procedure. In some cases, Step 1 and 

Step 2 may be combined (for example, if you use a model in Step 1 that considered both climate and host availability).

Step 1 Using plant hardiness zone matching or another method, identify the portion of the PRA area that 

has climatic conditions suitable for the pest’s survival based on its current global geographic distribution and any biological characteristics that may limit its ability to survive in the PRA area (such as 

temperature tolerance, humidity requirements, etc.). 

If you determine that suitable environmental conditions do not exist in the PRA area, or exist in protected areas only (e.g. glasshouses), state this in the risk assessment and conclude that the endangered area is Negligible. The assessment of the pest can stop at this point. 

Otherwise, proceed to Step 2. 

Plant hardiness zone matching. In this method you will use the global plant hardiness zone map 

developed by Magarey et al. (2008) to match the plant hardiness zones where the pest currently is 

found to the corresponding zones in the PRA area. 

1. Determine the current distribution of the pest through the world.

2. Using the map developed by Magarey et al. (2008), identify the plant hardiness zones in which 

the pest is currently distributed. If a pest is recorded in a country with several plant hardiness 

zones and there are no data on specific areas of its distribution, consider all hardiness zones in 

that country (if it is reasonable to do so). 

3. Identify the corresponding plant hardiness zones in the PRA area. 

Other methods. If you have specific information that can identify the climate requirements with 

more precision than hardiness zones, you may use this information to either refine the boundaries 

of the temperature zones identified using plant hardiness zone matching, or you can use another 

method of climate matching (e.g., NAPPFAST model, degree-day model, precipitation analysis, 

etc.). Regardless of the method you use, you must clearly identify the geographic area you have 

determined is likely to be climatically suitable for the pest by either providing a map or by clearly 

describing the boundaries of the area. 

Step 2 Determine the distribution of Type 1 hosts of the pest in the portion of the PRA area identified in 

Step 1 (i.e., in the area where climatic conditions are suitable for the pest’s establishment). 

Determine the distribution of Type 2 hosts in this area if there is a reasonably high level of certainty 

that the conditions for host status would be met there. 

If you determine that no suitable host material is found in the portion of the PRA area identified in 

Step 1 (except in protected areas, such as glasshouses), state this in the risk assessment and conclude that the endangered area for the pest is Negligible. The assessment of the pest can stop at 

this point. 

Otherwise, go to Step 3. 
Conducting Pest Risk Assesment in PPQ

Process 5: Collecting information and defining the endangered area

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-30

Step 3 Determine if any of the hosts present in the area of concern (identified in step 2) are of economic 

importance. As defined by ISPM No. 11, Supplement 2 (IPPC, 2004b), “economically” important 

hosts refers to both commercial and non-market (environmental) plants such as

 agricultural crops

 horticultural crops, ornamentals, nursery plants

 timber

 environmentally important non-commercial hosts such as threatened and endangered species, 

plants important to aesthetics of natural areas, ecologically important species, etc.

 plant species with a particular social importance, such as those to Native Americans

If you determine that none of the hosts plants identified in Step 2 are of economic importance, state 

this in the risk assessment and conclude that the endangered area for the pest is Negligible. The 

assessment of the pest can stop at this point.

Otherwise, go to Step 4 on page 2-31. 

Determine the area endangered by the pest by following the steps in this procedure. In some cases, Step 1 and 

Step 2 may be combined (for example, if you use a model in Step 1 that considered both climate and host availability).
Conducting Pest Risk Assesment in PPQ

Process 5: Collecting information and defining the endangered area

2-31 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Step 4 Based on the behavior and symptoms of the pest in the areas where it is currently distributed, 

determine whether the pest has the potential to impact the specific plant host species identified in 

step 3 by answering the questions below. 

Where the symptoms and/or the degree of damage caused by the pest vary throughout the pest’s 

distribution, you should place emphasis on the symptoms and damage the pest causes in regions 

most climatically similar to the area of concern (identified in Step 1) and on plant identified in Step 3.

1. In its current area of distribution, is the organism a known pest (or vector of a pest) of any of the 

hosts identified in Step 3? 

 For example: 

 Has the organism been described in the literature as a pest on one or more of the hosts identified in Step 3? 

 Do control programs for the pest exist on one or more hosts identified in Step 3? 

 Has the pest been documented to cause reductions in plant density, or impact ecological fitness of at least one of the non-commercial hosts identified in Step 3 (anywhere in the world)?

 Has the pest been documented to cause yield losses in commercial production of at least one 

host identified in Step 3? Consider both pre-harvest and post-harvest losses (losses due to 

unmarketable commodity). 

2. Based on the type of damage caused by the pest in its current distribution, could the pest (acting 

by itself or as a vector) cause damage to the hosts identified in Step 3? 

 For example:

 Is the type of damage or symptoms caused by the pest likely to result in pre-harvest losses of 

any commercially produced hosts identified in Step 3 (e.g., plant mortality, premature fruit 

drop, prevention of fruit set, dieback)?

 Is the type of damage or symptoms caused by the pest on any of the commercially produced 

commodities identified in Step 3 likely to result in post-harvest production losses (due to 

unmarketable commodity)?

 Is the type of damage or symptoms caused by the pest on any of the commercially produced 

commodities identified in Step 3 likely to result revenue losses resulting from a reduction in the 

value of the commodity (e.g., yellow/damaged leaves on a horticulture plant resulting in a 

lower market price; damaged fruit diverted from fresh market to juice market)?

 Is the type of damage caused by the pest likely to impact any of the environmentally or socially 

important plants identified in Step 3? 

If you answered yes to either Question 1 or 2, go to Step 5. 

If neither of the questions above could be answered yes, state in the risk assessment that the 

pest potential on economic hosts at risk is Negligible and conclude that the endangered area for the 

pest is Negligible. The assessment of the pest can stop at this point.

Determine the area endangered by the pest by following the steps in this procedure. In some cases, Step 1 and 

Step 2 may be combined (for example, if you use a model in Step 1 that considered both climate and host availability).
Conducting Pest Risk Assesment in PPQ

Process 5: Collecting information and defining the endangered area

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-32

Step 5 Describe the endangered area.

In most cases, you can describe the endangered area in terms of the Magarey et al. (2008) plant 

hardiness zones. As mentioned above, these zones provide a convenient method for bounding the 

endangered area because they divide the PRA area into distinct regions that have similar climates 

(in terms of average minimum winter temperatures) and, in many cases, hosts. To define the 

endangered area, simply identify the zones that have both suitable climate (as identified in Step 1) 

and available hosts (as identified in Step 2). In the risk assessment, state that the endangered area 

of the pest is considered to be within the identified zones, and explain your rationale and any uncertainty.

If you have used methods in Step 1 and Step 2 that more precisely identify the area of concern, you 

may define the endangered area in other terms; however, you must clearly describe the boundaries 

of this area (e.g., by state or county) and provide a map, if applicable. The identified area must have 

both suitable climate (Step 1) and economically important hosts at risk (Step 3 and Step 4). In the 

risk assessment, be sure to clearly explain your rationale and any uncertainty.

Determine the area endangered by the pest by following the steps in this procedure. In some cases, Step 1 and 

Step 2 may be combined (for example, if you use a model in Step 1 that considered both climate and host availability).
Conducting Pest Risk Assessment in PPQ

Process 6: Assessing uncertainty for risk elements

2-33 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Process 6: Assessing uncertainty for risk elements

Separating the uncertainty that arises due to lack of knowledge from the ratings 

of risk elements is important; ratings are made based only on the available 

evidence, not the uncertainty associated with the evidence. For instance, a 

given risk element should not be rated higher if there is a lot of uncertainty; 

rather, the rating should be assigned based on available evidence and the high 

level of uncertainty should be noted. At the same time, we recognize that a 

given risk element may be assigned a rating that may more or less accurately 

reflect the actual probability associated with that risk element, depending on 

the level of uncertainty. Higher levels of uncertainty could mean a given rating 

may be over- or under-estimating probability by one or more levels (e.g., a low 

rating with high uncertainty would truly be medium or high if we had more 

evidence on which to base our judgment). 

For some risk elements and where information is available, variability might 

be included in the rating; such situations should be documented in the text of 

the analysis. In cases with a high degree of variability, the analyst will typically 

make a conservative judgment resulting in a higher risk rating. This 

underscores the importance of describing uncertainty—including sources and 

magnitude—while at the same time maintaining judgments that are based on 

available evidence. 

We assess the uncertainty associated with each risk rating under likelihood of 

introduction (Process 7: Assessing the likelihood of introduction) and potential 

consequences of introduction (Process 8: Assessing potential consequences of 

introduction). Procedure 6-1: Assessing uncertainty for each risk element is a 

guide for assigning uncertainty ratings to each risk rating based on available 

evidence (modified after Andrews et al., 2004). Where appropriate, analysts 

should provide written explanations about the level of certainty associated with 

each rating. Gaps in knowledge should be specifically discussed, and possible 

areas of future research should be identified, as appropriate. 

Analysts should consult Supplement 4: Evaluation of Evidence on page 3-29

when assessing and assigning ratings of uncertainty. The supplement provides 

guidance on relating both the quality and quantity of evidence to the level of 

uncertainty. 
Conducting Pest Risk Assessment in PPQ

Process 6: Assessing uncertainty for risk elements

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-34

Procedure 6-1. Assessing uncertainty for each risk element

For each risk rating, assign an uncertainty rating based on the guidance in this procedure.

Uncertainty rating Description

Certain (C) Additional or better information is very unlikely to change the rating. 

This rating requires that:

 The risk rating is based on well-documented evidence (e.g., original 

research paper published in peer reviewed journal, or a survey conducted 

by an NPPO with an approved methodology).

 Area- or species-specific data are available. 

 Scientific consensus exists on methodological approach, or our agency has 

much experience with the pest. 

Moderately certain (MC) Additional or better information probably will not change rating.

Example justifications for this rating:

 Published articles or other documentation consists of review article of several original research studies. 

 Research or survey results are available but without detailed methodology. 

Moderately uncertain (MU) Additional or better information may or may not change rating.

Example justifications for this rating:

 Some area- or species-specific data are used, but most of the data were 

approximated or extrapolated from similar situations (i.e., research conducted in the areas of comparable climate, on a related host, or with a congeneric pest species). 

Uncertain (U) Reliable information is not available.

Example justifications for this rating:

 The risk rating is based on poorly documented methodology and results. 

 No area- or pest-specific data are available and no close approximations 

were used. 

 No reliable identification of the organism is available. 

 The pest biology, association with the host, or field prevalence are 

unknown.
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

2-35 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Process 7: Assessing the likelihood of introduction

We assess the likelihood of introduction by assigning High, Medium, Low, or 

Negligible ratings, as determined below in Risk Elements A and B. We note 

that in these risk elements we define “surviving” to mean avoiding mortality, 

remaining reproductively viable, and remaining with the commodity; this can 

include pests and pathogens that can remain dormant, live endophytically or 

remain latent in the host without showing signs or symptoms of infection. 

In Risk Element A: Likelihood of entry, we assess the likelihood of entry of the 

pest into the PRA area. We assess this likelihood by determining a baseline risk 

rating [Risk Element A1: Pest prevalence on the harvested plant part(s)] based 

on the likely pest prevalence or population on the harvested commodity. From 

that point, we determine if the pest prevalence will increase, decrease, or 

remain the same as the pest moves along the pathway. We specifically examine 

the likelihood that post-harvest processing before shipment (Risk Element A2: 

Likelihood of surviving post-harvest processing before shipment), as well as 

transport and shipping conditions will affect pest prevalence and thus entry 

potential (Risk Element A3: Likelihood of surviving transport and storage 

conditions of the consignment). We note that, in some cases, pest prevalence 

may increase after harvest. If we have evidence that this is likely to occur, we 

will specifically address this in the risk elements below. Additionally, although 

the volume of commodity entering the PRA area also impacts the entry 

potential of each pest, unless otherwise noted, we assume that the volume of 

commodity entering the country will be of a sufficient amount that entry and 

establishment is probable. 

In Risk Element B: Likelihood of establishment, we assess the likelihood that 

the pest will establish in the PRA area upon entry. Specific sub-elements 

include Risk Element B1: Likelihood of coming into contact with host material 

in the endangered area and Risk Element B2: Likelihood of arriving in the 

endangered area. 

We combine the likelihoods of entry and establishment to give an overall 

likelihood of introduction. We define the different categories of the overall 

likelihood of introduction as follows:

High. Pest introduction is highly likely to occur.

Medium. Pest introduction can occur, but for that to happen the exact 

combination of required events described needs to occur.

Low. Pest introduction is unlikely to occur because one or more of the 

required events is unlikely to happen, or the full combination of required 

events is unlikely to align properly in time and space.
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-36

Negligible. Pest introduction is highly unlikely to occur given the exact 

combination of events required for successful introduction.

Procedure 7-1. Assessing the likelihood of entry (Risk Element A)

Risk Element A: Likelihood of entry

Risk Element A1: Pest prevalence on the harvested plant part(s). Provide a 

qualitative rating for the size of the pest population that may be associated with 

the harvested plant part(s). This will be the baseline rating for likelihood of 

entry. For the baseline risk level, assume that the commodity was not subjected 

to any post-harvest treatments, including those that are usually associated with 

good industry practices, such as washing for mango. Determine the baseline 

risk ranking by deciding which of the criteria in Risk Element A1: Pest 

prevalence on the harvested plant part(s) best apply to the pest you are 

analyzing. Rate your uncertainty (Process 6: Assessing uncertainty for risk 

elements) and provide a narrative explanation for your decision. 

NOTE

The risk factors comprising the model for likelihood of introduction are interdependent and therefore the model is multiplicative rather than additive. Therefore, if any 

of the risk ratings in this section are Negligible for a certain pest, the overall likelihood of introduction for that pest becomes Negligible and the assessment for may 

stop.

NOTE

A Negligible rating is not possible for Risk Element A1: Pest prevalence on the harvested plant part(s) because only pests associated with the harvested commodity 

were selected for further analysis in Process 4: Creating the pest list and pest categorization. If a pest-free area was being considered as a part of the defined pathway, 

that pest would already have been removed from the pathway in the previous process.

NOTE

Type 2b hosts (conditional non-hosts) would have been included in the pest list 

(Procedure 4-3: Determining whether to include an actionable pest on the list) but 

not subject to further analysis if there was sufficient evidence and a reasonable level 

of certainty that the commodity met Type 2b host criteria (e.g., a non-host). Therefore, in this procedure, you should consider conditional hosts to be Type 2a hosts 

(that is, the commodity can serve as a host under specified conditions). Consult Supplement 3: Host Status on page 3-10 for more details on designating host status.
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

2-37 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Risk Element A2: Likelihood of surviving post-harvest processing before 

shipment. Assess the likelihood of the pest surviving through post-harvest 

processing, packing, and preparing the commodity for shipping. For this risk 

element, consider the post-harvest practices defined for the pathway in Process 

3 and how they affect the likelihood that the pest will remain with the 

commodity. Do not give a separate rating for the likelihood that the pest will 

survive post-harvest processing before shipment. Rather, depending on the 

likelihood, you should adjust the rating from Risk Element A1: Pest prevalence 

on the harvested plant part(s) (the baseline risk rating) up or down as 

appropriate, or keep it the same.

Consider the following:

The ease of detection of infested/infected commodity during 

packinghouse practices described in Process 3: Defining the pathway. 

Risk Element A1: Pest prevalence on the harvested plant part(s) 

IF THEN

Step 1 Any of the following statements apply:

 Evidence indicates that this organism always has a low association 

with the harvested plant parts. 

 The export area is recognized as an area of low pest prevalence 

(ALPP) for the pest in question.

 The commodity is a Type 2 host and the specific conditions required 

for it to serve as a host are unlikely to occur at any given time (e.g., for 

a Type 2a host, conditions generally are such that the pest can only 

rarely successfully attack the host, seasonality).

The baseline risk rating (A1) 

is Low. Continue to Step 2.

Any of the following conditions apply:

 Effective standard industry practices exist in the field and are applied 

before commodity is harvested.

 The commodity is not a preferred feeding (infection) site for the pest 

(e.g., the pest is occasionally associated with fruit, but generally feeds 

only on leaves).

 The commodity is a Type 2 host under specific environmental conditions, and those conditions occur sometimes but not constantly (e.g., 

for a Type 2a host, the conditions are such that the pest may successfully attack or infect the commodity at least some of the time, seasonality).

The baseline risk rating (A1) 

is Medium. Continue to Step 2.

Both of the following statements apply:

 The plant species to be imported is 1) a host and 2) the part(s) to be 

imported is a preferred feeding site of the pest. (For Type 2 hosts, the 

commodity is a Type 2a host under specific environmental conditions, 

and those conditions frequently or always occur).

 No standard industry field practices beyond minimal handling during 

harvest are being considered.

The baseline risk rating (A1) 

is High. Continue to Step 2.
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-38

The ease of removal of the pest from infested/infected commodity during 

standard packinghouse practices, e.g., washing, brushing, waxing. 

The quality standards and their possible effect on the pest’s association 

with the commodity.
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

2-39 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Risk Element A2: Likelihood of surviving post-harvest processing before shipment

IF THEN

Step 2 Evidence indicates that the entire pest population 

is highly likely to be killed or rendered inviable during processing (e.g., PPQ-approved irradiation treatment).

The rating is Negligible. Stop the risk assessment for the pest here. Summarize your findings and uncertainty.

Continue to Process 9: Summarizing the final 

risk ratings and uncertainty on page 2-63.

Evidence does not indicate that the entire pest 

population is highly likely to be killed or rendered 

inviable during processing.

Go to Step 3.

Determine which of the situations in Step 3 best applies to the pest you are analyzing. Provide your rating, rate 

your uncertainty, and provide a narrative explanation for your decision. 

Step 3 Reliable efficacy data or comparable evidence, provided by the NPPO of the exporting country or a 

comparable source, indicate that processing measures are likely to significantly reduce pest prevalence in the commodity (e.g., surface pests 

eliminated during washing, pathogens mitigated by 

washing with bleach). 

Do not automatically assume the efficacy of measures. Evidence needs to be specific and credible, 

and should be provided by the NPPO of the exporting country or other comparable source.

Decrease the baseline risk rating (A1) by 

one level.

A1 becomes A2

H M

M L

L Negl.*

*A change in the rating from Low to Negligible should 

be based on reliable evidence that the post-harvest 

processes described in the Process 3: Defining the 

pathwayare highly likely to kill or render inviable the 

pest population remaining from the previous step. If 

this is the case, the risk assessment process can 

stop here. Continue to Process 9: Summarizing the 

final risk ratings and uncertainty.

The pest is neither eliminated from the commodity 

nor does the population increase. In other words, you 

expect the pest prevalence in the commodity to 

remain more or less constant on the commodity 

through the post-harvest process.

The baseline risk rating does not change.

The rating for A2 stays the same as the rating 

for A1.

Either of the following apply:

 Evidence indicates that the prevalence of the 

pest can significantly increase in the period after 

harvest and before shipping.

 Safeguards for the commodity are absent, and 

this seems likely to lead to re-infestation (e.g., no 

insect-proof screens on field boxes or in the 

packinghouse).

In other words, you expect the pest prevalence in the 

commodity to increase during the post-harvest process.

Increase the baseline risk rating (A2) by one 

level.

A1 becomes A2

H H

M H

L M

Continue to Risk Element A3: Likelihood of surviving transport and storage conditions of the consignment.
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-40

Risk Element A3: Likelihood of surviving transport and storage conditions of 

the consignment. Here we assess the likelihood of the pest remaining with the 

commodity from packing through arrival. For this element, we consider the 

duration and conditions of transport and storage in the defined pathway, and 

the effects of these on pest survival. We also give the description of uncertainty 

associated with this rating.

Examples of factors you should consider include:

Duration of the life cycle of the pest in relation to time in transport and 

standard shipping conditions. For example, if transport is by air, the risk 

is likely to be high for most of the organisms because of the short duration 

of transport.

Vulnerability of the life stages during transport or storage. Some 

conditions (combination of temperature and storage time) could be close 

to the limits of cold tolerance for certain life stages.

Standard industry practices and their possible effect on the survival of the 

pest, if any.

NOTE

Do not give a separate rating for Risk Element A3: Likelihood of surviving transport 

and storage conditions of the consignment. Rather, depending on this likelihood, 

adjust the rating from Risk Element A2: Likelihood of surviving post-harvest processing before shipment up or down one level, or not at all, as appropriate.
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

2-41 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Risk Element A3: Likelihood of surviving transport and storage conditions of the consignment

IF THEN

Step 4 Either of the following apply:

 Conditions in transit or storage are equivalent in 

duration and temperature to an approved APHIS 

treatment against the same pest on the same 

commodity.

 Evidence indicates that the entire pest population 

is highly likely to be killed or rendered inviable 

during transportation or storage.

The rating is Negligible. Stop the risk assessment for the pest here. Summarize your finding 

and uncertainty.

Continue to Process 9: Summarizing the final 

risk ratings and uncertainty on page 2-63.

Neither of the above apply. Go to Step 5.

Determine which of the situations in Step 5 best applies to your pest, provide your rating, rate your uncertainty, 

and provide a narrative explanation for your decision. Then go to Procedure 7-2: Determining the likelihood of 

establishment (Risk Element B).

Step 5 Evidence indicates that the conditions of transport or 

storage in the defined pathway would significantly 

reduce the pest population with the commodity.

Decrease the risk rating for A2 by one level.

A2 becomes A3

H M

M L

L Negl.*

*A change in the rating from Low to Negligible should 

be based on reliable evidence that the post-harvest 

processes described in the Process 3: Defining the 

pathway are highly likely to kill or render inviable the 

pest population remaining from the previous step. If 

this is the case, the risk assessment process can 

stop here. Continue to Process 9: Summarizing the 

final risk ratings and uncertainty.

The transport and storage conditions in the defined 

pathway have no effect on the pest population. 

The risk rating does not change. The rating 

for A3 stays the same as the rating for A2.

Either of the following apply:

 Evidence indicates that the prevalence of the 

pest can significantly increase during shipping 

(specify conditions)

 Safeguards for the commodity are absent and 

this can lead to re-infestation

Decrease the risk rating for A2 by one level.

A2 becomes A3

H H

M H

L M
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-42

Procedure 7-2. Determining the likelihood of establishment (Risk Element B)

Risk Element B: Likelihood of establishment

In this risk element, we assess the pest opportunity for establishment based on 

availability of host and suitable climate. It consists of two independent risk 

elements, Risk Element B1: Likelihood of coming into contact with host 

material in the endangered area and Risk Element B2: Likelihood of arriving in 

the endangered area, which can be analyzed in either order. If the risk rating for 

either element is Negligible, the analysis of the pest can stop at that point.

Risk Element B1: Likelihood of coming into contact with host material in the 

endangered area. First, we assess how likely the pest is to come into contact 

with a suitable host. To do this, consider the following:

The endangered area identified in Process 5: Collecting information and 

defining the endangered area. 

Distribution of hosts in the endangered area. If applicable, consider if the 

pest requires alternate hosts to complete its life cycle, and if those hosts 

are present in the endangered area (e.g., the developmental cycle of some 

aphids).

The pest life stage(s) present on the imported commodity and information 

relating the likelihood of it coming into contact with a host and attacking/

infecting it. For example: 

known dispersal mechanisms (e.g., active or passive dispersal mode).

vectors needed for its dispersal and their presence in the endangered 

area.

proportion of survivors within a certain time period after leaving the 

commodity.

ability to complete development and/or reproduce on the commodity 

before or after arrival in the endangered area.

NOTE

It is essential to follow the order of steps when rating this risk element.
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

2-43 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Risk Element B1: Likelihood of coming into contact with host material in the endangered area

Use the following guidance to determine the risk rating for Risk Element B1. Provide your rating, rate your 

uncertainty, and provide a narrative explanation for your decision.

IF THEN

Step 1 Any of the conditions listed below apply to the pest situation you are 

assessing.

 The phenological stage of available hosts in the endangered area is 

unsuitable for pest establishment during the importation season, and 

the pest cannot survive until the host becomes suitable.

 A vector or other agent required for contact with the host to occur is 

absent in the endangered area or present but cannot acquire or transmit the pest (i.e., does not feed on the discarded plant part).

 The pest life stage present is highly unlikely to move on its own from 

the commodity to a new host and 

 is highly unlikely to develop into a dispersing life stage, OR 

 the dispersing life stage of the pest is very short-lived and very susceptible to different mortality factors (e.g., exposure to elements, natural enemies, etc.).

The rating for Risk Element 

B1 is Negligible. Stop the risk 

assessment for the pest here. 

Summarize your finding and 

uncertainty.

Continue to Process 9: Summarizing the final risk ratings 

and uncertainty.

None of the above conditions apply. Go to Step 2.

Step 2 Any of the conditions listed below apply to the pest situation you are 

assessing.

 Conditions necessary for the pest’s transmission to the host are seldom met (e.g., temperature, moisture).

 Few natural hosts exist in the endangered area. For example:

 very low host density in the stands or their populations are sparsely 

distributed through the endangered area.

 hosts are tropical/subtropical plants only and not commercially produced. 

 pest has a restricted host range.

 Vector or other dispersal agent is present (if required), but with low 

prevalence.

 Dispersing life stage of the pest has limited ability to disperse naturally. 

The rating for Risk Element 

B1 is Low.

None of the above conditions apply. Go to Step 3.
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-44

Step 3 Given that the pest is capable of dispersing on its own or through a widely 

prevalent vector, any of the conditions listed below apply to the pest situation you are assessing.

 Suitable hosts are widely established in only a limited portion of the 

endangered area (e.g. commercially-produced warm climate crops 

when the endangered area includes both temperate and warm climate 

areas).

 Suitable hosts are not continuously distributed throughout the endangered area (e.g., botanical gardens).

 The commodity may arrive in the endangered area at times when phenology of the host is not suitable.

 The environmental requirements necessary for the pest’s successful 

transfer to and establishment on new hosts in the endangered area are 

met only under certain conditions (e.g., season, temperature, humidity, 

etc.).

The rating for Risk Element 

B1 is Medium.

None of the above conditions apply. Go to Step 4.

Step 4 Given that the pest is capable of dispersing on its own or through a widely 

prevalent vector, the following conditions should apply to the pest you are 

assessing.

 Suitable hosts are widely and regularly distributed throughout the 

entire endangered area.

 Suitable hosts in the endangered area are available regardless of season.

 No alternate hosts are needed to complete development or, if needed, 

are widely available.

 All environmental requirements are usually met for the pest’s transfer 

to a suitable host in the endangered area (e.g., wind, water, temperature).

The rating for Risk Element 

B1 is High.

Risk Element B1: Likelihood of coming into contact with host material in the endangered area

Use the following guidance to determine the risk rating for Risk Element B1. Provide your rating, rate your 

uncertainty, and provide a narrative explanation for your decision.

IF THEN
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

2-45 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Risk Element B2: Likelihood of arriving in the endangered area. In most cases, 

we have little information about commodity movement in the PRA area. For 

this reason, in the absence of specific evidence, we assume that commodities 

move throughout the PRA area in proportion to consumer population size, with 

more populous areas getting more of the commodity than less populous areas. 

This assumption implies that larger volumes of the commodity will be moved 

to more populated areas, thus increasing the risk of pests entering those areas. 

We, however, are not taking into account the actual volumes of the 

commodities arriving in different areas as such information is not readily 

available and is prone to market fluctuations. 

If specific information exists about where the commodity is most likely to 

move, its shipping frequency, or seasonality, this information can be used to 

determine more precisely the likelihood of the pest finding a suitable climate. 

For example, if we have evidence that a commodity would be imported only to 

an area where certain ethnic markets are located, and this region is outside the 

endangered area, or that the commodity is intended for specific seasons (e.g., 

holidays), such information can be used to lower the rating (see Step 2). 

If the endangered area described in Process 5: Collecting information and 

defining the endangered area is defined in terms of temperature or plant 

hardiness zones, we may use Supplement 2: Plant Hardiness Zones Area and 

Population Analysis to easily find the percentage of the U.S. population that 

occurs within the zones corresponding to the endangered area. If the 

endangered area is defined in another way, we use the latest U.S. census to 

calculate the total population in the PRA area and in the endangered area. We 

calculate the proportion of the population in the endangered area relative to the 

population in the PRA area. 

NOTE

A rating of Negligible is not possible for Risk Element B2, because an endangered 

area has been identified within the PRA area, and we assume that any commercial 

trade volume is significant enough for there to be some risk.
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-46

Risk Element B2: Likelihood of arriving in the endangered area

Determine the base rating for this element using the criteria below. 

IF THEN

Step 1 Less than 10 percent of the population lives within 

the endangered area. 

The rating for Risk Element B2 is Low. Go to 

Step 2.

Between 10 and 25 percent of the population lives 

within the endangered area. 

The rating for Risk Element B2 is Medium. 

Go to Step 2.

Greater than 25% of the population lives within the 

endangered area. 

The rating for Risk Element B2 is High. Go 

to Step 2.

Based on the criteria in Step 2, adjust the rating from Step 1 up or down as appropriate. Then go to 

Procedure 7-3: Determining the combined likelihood of establishment.

Step 2 You do not have specific information about the distribution of the commodity (including its destination, 

shipping season, frequency, etc.), or what is known 

about its distribution is unlikely to change the risk.

Your analysis of Risk Element B can stop 

here. Continue to Procedure 7-3: Determining 

the combined likelihood of establishment.

At least one of the following statements applies:

 The commodity is likely to solely be distributed in 

specialty markets outside of the endangered 

area. 

 The commodity has a very short shipping season 

(e.g. 1 month or less) 

 The commodity will only be imported infrequently 

(e.g., less than 5 times) in small quantities during 

times of year that would prevent pest establishment (e.g., winter months).

Decrease the risk rating for B2 by one level.

B2 becomes B2’

H M

M L

L Negl.*

*Requires a high degree of uncertainty (i.e., a rating 

of C or MC); otherwise, leave as Low.

Either of the following statements apply:

 The commodity is likely to be distributed mainly to 

markets within the endangered area throughout 

the year, including seasons that are favorable for 

pest establishment.

 Either high volumes or frequency of imports justify increasing the risk rating.

Increase the risk rating for B2 by one level.

B2 becomes B2’

H H

M H

L M
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

2-47 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Procedure 7-3. Determining the combined likelihood of establishment

Risk Element B: Combined likelihood of establishment

The matrix in this procedure is used to combine Risk Element B1: Likelihood 

of coming into contact with host material in the endangered area and Risk 

Element B2: Likelihood of arriving in the endangered area in order to 

determine the overall likelihood of the pest becoming established in the 

endangered area via the specific commodity import pathway. If Risk Element 

B1 is Negligible, the overall likelihood of establishment (Risk Element B) is 

Negligible and no further analysis is needed. This is shown as “no analysis” in 

the matrix below. The other values for the Likelihood of Establishment are 

found as the intersection in the matrix for the ratings of Risk Elements B1 and 

B2. 

Risk Elements B1 and B2 will be rated High when the pest is likely to come in 

contact with suitable hosts in the endangered area (during times favorable for 

pest establishment) and it coincides with a large consumer presence in the area. 

If either risk element is not ranked High, then Risk Element B1: Likelihood of 

coming into contact with host material in the endangered area is the 

“weighting” factor for the likelihood of establishment (e.g., a combination of 

High and Medium ratings becomes High). The assumption is that pest’s ability 

to come in contact with hosts is an intrinsic factor for that pest-commodity 

association and remains stable regardless of the area of the commodity’s 

distribution. Distribution of the commodity is more likely to be affected by 

changes in market demands or in demographics.
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-48

Determining the overall likelihood of introduction

If the overall likelihood of introduction is High, this implies possible 

continuous entries of sizable pest populations (Risk Element A: Likelihood of 

entry is High or Medium) and high likelihood of the commodity being moved 

to parts of the Endangered Area with the High consumer population and of the 

pest’s High ability to transfer to a new host (Risk Element B: Likelihood of 

establishment is High). If the likelihood of pest entry (Risk Element A: 

Likelihood of entry) is Low and the likelihood of establishment in the 

endangered area (Risk Element B: Likelihood of establishment) is High, the 

overall rating will be Medium. Similarly, if the likelihood of introduction is 

Low, this implies possible irregular entries of smaller pest populations (Risk 

Element A: Likelihood of entry is Low or Medium) and limited opportunity for 

the pest to be moved to areas with high consumer populations and/or limited 

ability of the pest to come into contact with host material (Risk Element B: 

Likelihood of establishment is Low).

Risk Element B: Combined likelihood of establishment

Combine Risk Elements B1 and B2 using the matrix in this procedure to determine the rating for Risk Element B. In the 

risk assessment, state the rating, rate your uncertainty, and provide a narrative explanation for your decision.

Risk Element B1: 

Likelihood of coming into contact with host 

material in the endangered area

Negligible Low Medium High

Risk Element B2: 

Likelihood of arriving in

the endangered area

High

no analysis

M M H

Medium L M H

Low L M M
Conducting Pest Risk Assessment in PPQ

Process 7: Assessing the likelihood of introduction

2-49 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Procedure 7-4. Determining the overall likelihood of introduction

The rating for overall Likelihood of Introduction is weighted towards pest 

establishment because this element is more important. If the pest cannot 

establish then the likelihood of entry becomes irrelevant. Once a pest has 

entered, we are most concerned with its establishment potential.

Risk Element B: Combined likelihood of establishment

Combine the ratings for the likelihoods of entry (Risk Element A) and establishment (Risk Element B) into a rating for the 

overall likelihood of introduction according to the matrix below. If either entry (Risk Element A) or establishment (Risk 

Element B) is rated Negligible, the overall likelihood of introduction is Negligible and no further analysis is needed. 

Risk Element B: 

Likelihood of Establishment

Low Medium High

Risk Element A: 

Likelihood of Entry

High M M H

Medium L M H

Low L M M
Conducting Pest Risk Assessment in PPQ

Process 8: Assessing potential consequences of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-50

Process 8: Assessing potential consequences of introduction

The purpose of this process is to determine whether the introduction of the pest 

would result in unacceptable economic consequences in terms of the potential 

agricultural, environmental, and social impacts that could result from the pest 

establishing in the endangered area. We evaluate the consequences of 

introduction without respect to the pathway of introduction by assuming a 

hypothetical situation where the pest is introduced and fully expressing its 

potential economic consequences in the endangered area. 

We evaluate both direct impacts (i.e., impacts resulting from pest damage to 

host plants) and trade impacts. In general, we do not identify or evaluate 

indirect impacts beyond potential trade impacts, even though we acknowledge 

that such impacts are often unacceptable. However, it is not the purpose of this 

analysis to estimate the magnitude of the total impacts, but instead only to 

determine whether a given pest is likely to cause unacceptable economic 

consequences. Therefore, it is sufficient to limit our evaluation of potential 

consequences to the direct pest effects and the potential impacts to trade. Any 

other unacceptable impacts would likely occur as a result of one or more direct 

or trade impacts. 

Similarly, although in practice the total consequences of introduction of a pest 

would be dependent on the rate and manner of spread in the PRA area, 

because, again, we are not estimating the magnitude of the total consequences, 

it is sufficient for the purposes of this analysis to simply determine if the 

spread potential of the pest is significant enough that it would be likely to 

spread throughout the endangered area within a reasonable period of time. 

Pests that have a Low or Negligible spread potential are not likely to cause 

unacceptable impacts unless the damage potential of the pest is High.

Pests that are likely to cause unacceptable consequences are termed “threshold 

pests”; those that are not likely to cause unacceptable consequences are termed 

“non-threshold pests.” By using this approach we explicitly acknowledge that 

non-threshold pests may cause some damage in the PRA area; however, that 

level of damage is expected to be low enough that routine port-of-entry 

inspection will be sufficient to mitigate the risk associated with their possible 

entry. Threshold pests, on the other hand, are expected to cause a level of 

damage that may warrant additional phytosanitary measures beyond routine 

port-of-entry inspection (to reduce their likelihood of entry) in order to meet 

the acceptable level of risk. 

A pest is not likely to cause unacceptable direct impacts in the endangered area 

if any of the following criteria applies:

The pest is not likely to cause significant losses to commercial or noncommercial plants as a result of mitigating conditions in endangered area.
Conducting Pest Risk Assessment in PPQ

Process 8: Assessing potential consequences of introduction

2-51 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Should the pest become established in any portion of the endangered area, 

its ability to move beyond its initial point of introduction is very limited, 

so that spread in the endangered area is likely to be very slow or 

negligible, limiting any potential damage to a localized area.

A pest is not likely to cause unacceptable trade impacts if hosts of the pest are 

not exported, if the pest already occurs in countries importing commodities 

from the endangered area that are likely to be pathways for moving the pest, or 

if the countries already require phytosanitary measures for the exported 

commodity that will be effective against the pest. 

In determining whether a pest will cause unacceptable damages to the PRA 

area, we evaluate how the pest is behaving in its current area of distribution. 

When the evidence suggests that a given pest is behaving differently in 

different parts of its distribution, we place emphasis on how the pest behaves in 

the parts of the distribution most similar to the endangered area. In many cases, 

there is little evidence to predict how a pest will behave in the endangered area. 

In these circumstances, our uncertainty rating may be high, and such pests 

should be explicitly identified in the notes to the risk managers. 

Once it can be shown that the consequences of the pest’s establishment in the 

PRA area will likely exceed a certain threshold of damage, the pest is 

determined to be a threshold pest. It is beyond the scope of this analysis to 

attempt to quantify, estimate, or predict the magnitude of potential pest effects. 

It is important to understand, therefore, that the analysis of a particular pest 

will not necessarily identify all of the potential impacts that would likely result 

from its introduction. This approach is consistent with ISPM No. 11 (2004b), 

which acknowledges that detailed analysis of the consequences of introduction 

is not necessary when it is widely agreed that pest introduction will have 

unacceptable consequences. The approach is sufficient for most pests analyzed 

in commodity import assessments., but a more detailed economic analysis of 

potential consequences can be conducted separately, if needed.
Conducting Pest Risk Assessment in PPQ

Process 8: Assessing potential consequences of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-52

Procedure 8-1. Determining the potential direct impacts (Risk Element C)

Risk Element C: Determining the potential direct impacts

Risk Element C1: Damage potential in the endangered area. Consider the 

climate and cultural conditions that exist in the endangered area and decide 

whether the introduction of the pest in the endangered area will result in 

unacceptable economic (including environmental and social) damage or loss to 

plants in the endangered area. Assume a hypothetical situation where the pest 

is introduced throughout the endangered area and fully expressing its potential 

economic consequences. In general, you should consider only evidence related 

to plants identified in Step 3 of Procedure 5-2: Defining the endangered area. 

Do not consider symptoms/damage on unrelated plants, unless they are very 

similar.
Conducting Pest Risk Assessment in PPQ

Process 8: Assessing potential consequences of introduction

2-53 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Risk Element C1: Damage potential in the endangered area

Step 1 Identify the climatic and cultural conditions in the endangered area that are likely to impact the damage 

potential of the pest.

Consider: 

 climatic conditions that would affect pest population and/or virulence. 

 host distribution (including amount of production of cultivated hosts and abundance of environmental 

hosts) in the endangered area. 

 conditions that would affect the status of conditional hosts. 

 current standard production practices of the cultivated hosts at risk (including any organic production). 

Note any practices that would likely mitigate the consequences of establishment of the pest. Examples of 

such practices include:

 pesticides routinely applied for other pests that would also control the pest being assessed.

 cultural control practices such as field sanitation, crop rotation, etc.

 planting of host-resistant varieties and/or clean stock. 

 the presence and distribution of similar pests in the endangered area, including natural areas. Note the 

impact these pests currently cause in the endangered area. Consider questions such as

 how would the damage caused by this pest compare? 

 how are similar pests in the endangered area being controlled (including natural controls), if at all? 

 if control practices are in place, would they also mitigate this pest?

Continue to Step 2.

Step 2 With respect to the conditions in Step 1, estimate the damage potential of the pest in the endangered area in 

terms of percent losses. Then go to Step 3. 

Factors to consider:

 how widespread each condition is in the endangered area (for example, consider standard production 

practices of commercial hosts vs. organic production, presence and density of environmental/wild hosts, 

etc.).

 host preference and status. 

 type of damage caused by the pest on hosts present in the endangered area (see Step 4 of 

Procedure 5-2: Defining the endangered area). 

 ease of control. Are pesticides/treatments for the pest readily available? 

 ease of detection (affects surveillance and monitoring costs). 

 is pest likely to be mitigated/controlled by any of the conditions in the endangered area?
Conducting Pest Risk Assessment in PPQ

Process 8: Assessing potential consequences of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-54

Risk Element C1(a): Damage potential to commercial hosts

IF THEN

Step 3 Either of the following statements apply.

 The introduction of the pest in the endangered area would likely result 

in 10 percent or greater yield losses in at least one commercially cultivated host. 

 The introduction of the pest would likely result in a significant increases 

in costs of production beyond normal annual fluctuations. For example, 

consider increased costs to producers due to the implementation of 

additional control practices (or regimes) in the endangered area 

(beyond those already in place for the control of similar pests) and/or 

costs associated with surveillance and monitoring. 

Potential damage in the 

endangered area is significant. 

In the risk assessment, indicate 

that the pest meets the criteria 

for having the potential to 

cause unacceptable damage in 

the endangered area. Rate 

your uncertainty, summarize 

the evidence, and then proceed 

to Step 5.

Neither of the above statements apply. Go to Step 4.

Risk Element C1(b): Damage potential to non-commercial hosts

IF THEN

Step 4 Either of the following statements apply.

 The type of damage or symptoms caused by the pest in the endangered area would likely result in population reduction (beyond normal 

fluctuations ) of threatened and endangered, or socially and other environmentally important plants. Do not consider “quality” losses. Do not 

consider host congeners unless you have evidence the pest damages 

multiple congeners.

 The introduction of the pest in the endangered area would likely result 

in significant reductions of amenity values (due to obviously and visibly 

damaged plants) beyond normal annual fluctuations. 

Potential damage in the 

endangered area is significant. 

In the risk assessment, indicate 

that the pest meets the criteria 

for having the potential to 

cause unacceptable damage in 

the endangered area. Rate 

your uncertainty, summarize 

the evidence, and then proceed 

to Step 5.

Neither of the above statements apply. Potential damage in the 

endangered area is not significant.

In the risk assessment, indicate 

that the pest does not meet the 

criteria for having the potential 

to cause unacceptable damage in the endangered area, 

rate your uncertainty, and summarize the evidence. Continue 

to Procedure 8-4: Determining 

potential trade impacts.
Conducting Pest Risk Assessment in PPQ

Process 8: Assessing potential consequences of introduction

2-55 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Risk Element C2: Spread potential

In this risk element, you will determine the likelihood that the pest will spread 

beyond its initial point of introduction within a reasonable amount of time. 

Pests that have a Low or Negligible spread potential are not likely to cause 

unacceptable impacts unless the damage potential is High.

Risk Element C2: Spread potential

Step 5 Consider the following factors:

 current distribution and spread patterns of the pest. For example, is the pest spreading rapidly around the 

world? How quickly is the distribution of the pest expanding, particularly in areas it has been introduced 

that are climatically similar to the endangered area?

 abundance and continuity of natural hosts in the areas in endangered area. If applicable, consider if the 

pest requires alternate hosts to complete its life cycle. 

 dispersal potential 

 natural dispersal mechanisms (flight, vectors, rain/wind, etc.) and availability of such mechanisms in the 

endangered area.

 intentional or unintentional movement of infected or infested plants or plant products (for example, a 

pathogen infecting only leaves may not likely be moved by humans if the leaves are not part of the commodity). 

 intentional movement of the organism.

 ability of the organism to hitchhike on conveyances.

 relevant life history of the pest. 

 life stages (including duration).

 reproductive strategies (fecundity, parthenogenesis, alternating generations, etc.).

 adaptive characteristics (dormancy, expansion of a host range, climatic tolerance, i.e., supercooling, 

etc.).

 ease of detection.

 control or mitigation practices in the endangered area that would limit spread.

Continue to Step 6.
Conducting Pest Risk Assessment in PPQ

Process 8: Assessing potential consequences of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-56

IF THEN

Step 6 The pest is already present in some portion of the endangered area. Go to Step 7.

The pest is not already present in the endangered area. Go to Step 8.

Step 7 The pest has been present in the endangered area for more than 10 

years and is not part of an official program for eradication, containment, or 

area-wide control.

Spread potential is not significant.

In the risk assessment, indicate 

that the pest does not have a 

significant spread potential, 

rate your uncertainty, and summarize the evidence. Continue 

to Procedure 8-3: Additional 

analysis for pests with undetermined trade impact.

The pest has been present in the endangered area for fewer than 10 

years.

Go to Step 8.

Step 8 Evidence indicates that the pest is spreading or has spread in other 

parts of the world—that is, the distribution of the pest is expanding, particularly in areas where it has been introduced that are climatically similar to 

the endangered area.

Spread potential is significant.

In the risk assessment, indicate 

that the pest has a significant 

spread potential, rate your 

uncertainty, and summarize the 

evidence. Continue to 

Procedure 8-2: Determining if 

the pest is likely to cause unacceptable direct economic 

impacts.

There is no evidence that the pest is spreading or has spread in other 

parts of the world.

Go to Step 9.
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Process 8: Assessing potential consequences of introduction

2-57 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Step 9 Any of the following statements apply.

 The pest requires specific vectors for dispersal that are not present in 

the endangered area.

 The pest has limited natural dispersal potential and is unlikely to be 

moved by humans. Consider the likelihood of humans moving the pest 

from an area of establishment in the endangered area to another portion of the endangered area (e.g., purposeful movement, accidental 

movement on plant parts in domestic trade, movement on fomites, 

etc.). Do not consider interception records.

 The dispersal abilities of the pest would not allow it to access the available hosts (e.g., hosts are patchy/non-continuously distributed, separated by geographic barriers, non-persistent vectors).

 The dispersal stage requires a specific combination of conditions 

which rarely occur together (e.g., wind-rain event at a particular life 

stage).

Spread potential is not significant.

In the risk assessment, indicate 

that the pest does not have a 

significant spread potential, 

rate your uncertainty, and summarize the evidence. 

Procedure 8-3: Additional analysis for pests with undetermined trade impact.

None of the above statements apply. Spread potential is significant.

In the risk assessment, indicate 

that the pest has a significant 

spread potential, rate your 

uncertainty, and summarize the 

evidence. Go to Procedure 8-2: 

Determining if the pest is likely 

to cause unacceptable direct 

economic impacts.

IF THEN
Conducting Pest Risk Assessment in PPQ

Process 8: Assessing potential consequences of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-58

Procedure 8-2. Determining if the pest is likely to cause unacceptable direct 

economic impacts

Determine the likelihood of the pest to cause unacceptable direct economic impacts by combining the ratings 

for the damage potential (Risk Element C1) and spread potential (Risk Element C2) according to this procedure. 

IF AND THEN

The damage potential (C1) 

was not significant.

The pest is not likely to cause unacceptable direct 

impacts in the endangered area.

Go to Procedure 8-4: Determining potential trade 

impacts.

The damage potential (C1) 

was significant.

The spread potential (C2) 

was significant.

The pest is likely to cause unacceptable direct economic impacts in the endangered area.

To analyze trade impacts (only necessary upon special 

request), go to Procedure 8-4: Determining potential 

trade impacts.

Otherwise, continue to Process 9: Summarizing the final 

risk ratings and uncertainty on page 2-63 if the likelihood of introduction has already been completed for this 

pest, or to Process 7: Assessing the likelihood of introduction on page 2-35 if the likelihood of introduction has 

not been completed.

The damage potential (C1) 

was significant.

The spread potential (C2) 

was not significant.

The likelihood of the pest causing unacceptable 

direct economic impacts cannot be determined at 

this point. Continue to Procedure 8-3: Additional analysis for pests with undetermined trade impact.
Conducting Pest Risk Assessment in PPQ

Process 8: Assessing potential consequences of introduction

2-59 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Procedure 8-3. Additional analysis for pests with undetermined trade impact

Pests that have a significant damage potential but do not have a significant spread potential may or may not 

meet the criteria for causing unacceptable direct impacts. Follow this procedure to determine the likelihood of 

causing unacceptable direct economic impacts for a pest whose likelihood of causing unacceptable direct economic impacts could not be determined using Procedure 8-2: Determining if the pest is likely to cause unacceptable direct economic impacts.

IF THEN

Evidence suggests that the pest is capable of causing 

major damage (i.e., 50 percent field losses) and it meets 

one of the following criteria:

 Most of the commercial production of one or more of 

the pest’s hosts occurs within a small area, such as a 

single hardiness zone, county, or other defined region. 

 The pest is associated with a threatened or endangered species found in the endangered area. 

Consider the pest to meet the threshold of causing 

unacceptable direct economic impacts in the endangered area.

The above does not apply. Consider the pest to not be likely to cause unacceptable direct economic impacts in the endangered area 

and analyze the trade impacts using Procedure 8-4: 

Determining potential trade impacts.

If potential trade impacts have already been analyzed and 

they are not likely to significant, conclude that the pest 

does not meet the threshold for causing unacceptable 

economic impacts.
Conducting Pest Risk Assessment in PPQ

Process 8: Assessing potential consequences of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-60

Procedure 8-4. Determining potential trade impacts

Risk Element D: Determining potential trade impacts

Based on the total market for the host commodities at risk (identified in Step 3

of Procedure 5-2: Defining the endangered area), determine if introduction of 

the pest in the endangered area would likely result in unacceptable trade 

impacts to the PRA area, in terms of losses of existing export markets.

Risk Element D1: Determining export markets at risk. 

NOTE

Trade impacts are analyzed for the entire PRA area, not just the endangered area, 

because the entire PRA area may be impacted if the pest is able to establish in any 

portion of it. For example, trading partners may impose provisional measures until it 

can be demonstrated that the pest will not establish outside of the defined endangered area. Should the pest become established in the PRA area, there may be 

costs associated with demonstrating and maintaining pest-free areas (e.g., costs 

associated with surveys).

Risk Element D1: Export markets at risk

IF THEN

Step 1 Determine whether plant products potentially affected by the 

pest have been exported from 

the PRA area in the past five 

years. Consider the specific plant 

part(s) being exported, and the 

pest association with these parts.

No host commodities are currently being exported.The pest is not a threshold 

pest. 

The analysis of potential trade 

impacts can stop here. Continue 

to Process 9: Summarizing the 

final risk ratings and uncertainty

on page 2-63.

Host commodities are currently 

being exported.

Go to Step 2.

Step 2 Identify the export markets of the 

host commodities identified in 

step 1 from the PRA area and 

determine which of these markets are currently free from the 

pest or consider the pest to be of 

quarantine significance. 

No export market is currently free 

from the pest (i.e., the pest is 

currently distributed everywhere 

that host commodities are currently being exported from the 

PRA area).

The pest is not a threshold 

pest. 

The analysis of potential trade 

impacts can stop here. Continue 

to Process 9: Summarizing the 

final risk ratings and uncertainty

on page 2-63.

At least one export market for at 

least one host commodity is currently free from the pest.

Go to Step 3.
Conducting Pest Risk Assessment in PPQ

Process 8: Assessing potential consequences of introduction

2-61 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Risk Element D2: Likelihood of trading partners imposing additional 

phytosantiary requirements. In completing Step 4, consider factors such as:

degree to which the exported commodity is processed. For example, is the 

exported commodity processed in such a way that the pest has a 

negligible likelihood of being moved with the commodity?

current phytosanitary requirements already in place for the commodity. 

For example, do trading partners already require phytosanitary measures 

(for other pests) that would also mitigate this pest? (PCIT/EXCERPT)

likelihood of taking action against the pest. For example, do trading 

partners currently maintain regulations for the pest? Do they currently 

take action on similar pests? Are they unlikely to take action against the 

pest because it is unlikely to establish in the country? (PCIT/EXCERPT; 

Trade director) 

importance of domestic production in the trading countries. For example, 

do trading partners have significant domestic production of any hosts 

associated with the pest? (FAO Stats). Do they export significant amounts 

of host commodities to countries that are free of the pest? (GTIS for 

trade; CABI, etc. for pest freedom)

trade with other countries where the pest is currently distributed. For 

example, are trading partners currently importing host commodities from 

other countries where the pest is distributed? Under what conditions? 

What kinds of phytosanitary measures are required? 

Step 3 Determine the export value of 

host commodities that are typically exported to countries free 

from the pest or to countries 

where the pest is considered to 

be of quarantine significance. 

In general, you should start with 

major export commodities

The value of any commodity 

exported to countries free from 

the pest is greater than 10 percent of the total export value of 

that commodity.

Go to Step 4.

The export value of every commodity exported to countries free 

from the pest is less than 10 percent of the total export value of 

that commodity.

The pest is not a threshold 

pest. 

The analysis of potential trade 

impacts can stop here. Continue 

to Process 9: Summarizing the 

final risk ratings and uncertainty

on page 2-63.

Risk Element D1: Export markets at risk

IF THEN
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Process 8: Assessing potential consequences of introduction

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-62

Risk Element D2: Likelihood of trading partners imposing additional phytosanitary requirements

IF THEN

Step 4 Trading partners that are currently free from the pest would be likely 

to impose an export ban on host commodities, or require the implementation of additional phytosanitary measures on them as a condition of export.

The pest is a threshold pest. 

If you’ve already completed the 

likelihood of introduction for this 

pest, continue to Process 9: 

Summarizing the final risk ratings 

and uncertainty on page 2-63. 

Otherwise, go to Process 7: 

Assessing the likelihood of introduction on page 2-35.

The above does not apply. The pest is not a threshold 

pest. 

The analysis of potential trade 

impacts can stop here. Continue 

to Process 9: Summarizing the 

final risk ratings and uncertainty

on page 2-63.
Conducting Pest Risk Assessment in PPQ

Process 9: Summarizing the final risk ratings and uncertainty

2-63 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Process 9: Summarizing the final risk ratings and uncertainty

For this process, we briefly summarize the results for the pests analyzed in 

Process 7: Assessing the likelihood of introduction and Process 8: Assessing 

potential consequences of introduction. For each pest, we separately present 

the overall result or rating for the likelihood of introduction assessment and the 

overall result for the consequences assessment. 

The final result of the qualitative uncertainty assessment should be the 

identification of most relevant sources of uncertainty and technical means for 

reducing them, as well as the evaluation of the overall effect of uncertainty 

sources on the risk estimate.

NOTE

The results for likelihood and consequences of introduction are not combined to give 

one overall risk rating. We use these overall results to determine which of the analyzed pests are candidates for risk management and which are not. If warranted, we 

also provide a summary of the uncertainty associated with each pest analysis. 

Procedure 9-1. Summarizing the final risk ratings and uncertainty

Follow the steps of this procedure to summarize the final risk ratings and uncertainty.

IF THEN

The pest meets at least one of the following criteria: 

 no portion of the PRA area is likely to be endangered by the pest (i.e., the area endangered by 

the pest is Negligible).

 does not meet the threshold to likely cause 

unacceptable consequences of introduction.

 received a Negligible overall risk rating for likelihood of introduction. 

The pest is not a candidate for risk management.

In the “Summary and Conclusions” section of the risk assessment, summarize this list of pests in a table that contains, for 

each pest, the reason the pest is not a candidate for risk management. For each pest, if warranted, provide an uncertainty 

statement in the table; this statement should focus on identification of the most relevant sources of uncertainty and technical 

means for reducing them, as well as the evaluation of the overall 

effect of uncertainty sources on the risk estimate. 

The pest meets the following criteria:

 meets the threshold to likely cause unacceptable consequences of introduction.

 received an overall risk rating for likelihood of 

introduction above Negligible.

The pest is a candidate for risk management.

In the “Summary and Conclusions” section of the risk assessment, summarize this list of pests in a table that contains, for 

each pest, the likelihood of introduction overall rating (i.e., High, 

Medium, or Low). Note that the results of the consequences of 

introduction assessment do not need to be included in this table, 

as all these pests meet the threshold for unacceptable consequences. For each pest, if warranted, provide an uncertainty 

statement in the table; this statement should focus on identification of the most relevant sources of uncertainty and technical 

means for reducing them, as well as the evaluation of the overall 

effect of uncertainty sources on the risk estimate. 

Continue to Process 10: Risk mitigation notes on page 2-67.
Conducting Pest Risk Assessment in PPQ

Risk Management in pest risk analysis

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-64

Stage 3: Risk Management

Risk Management in pest risk analysis

The core elements of pest risk analysis are risk assessment and risk 

management. Pest risk management is defined by the IPPC as the “evaluation 

and selection of options to reduce the risk of introduction and spread of a pest” 

(ISPM No. 5: IPPC, 2012). This means that mitigations may be applied at any 

point in the production chain to reduce likelihood of entry (e.g., pre-border); or 

to reduce likelihood of establishment or spread (e.g., post-border). 

There are three general aspects to risk management that should be considered: 

policy, analytical and operational. The policy aspect is that part of risk 

management where overall policy is considered, including the appropriate 

level of protection/acceptable level of risk. Several key principles of the SPS 

and IPPC apply to the policy aspects of risk management, including in 

particular the

application of the appropriate level of protection (ALOP), 

principle of least trade restrictive measures (minimal impact), 

principle of non-discrimination (including national treatment),

principle of managed risk, and 

principle of equivalence. 

Non-technical factors (e.g., social and political concerns) may be considered 

under the policy component of risk management, or for instance, priorities for 

risk management may be decided by broader policy issues. Since zero-risk is 

not a reasonable option, risk management should focus on reduction of risk 

that can be justified and is feasible within the limits of available options and 

resources. In any case, the overarching policy of the NPPO, together with any 

country/commodity-specific policies, is usually the main driver in the ultimate 

decision-making stages for risk management. Usually the policy aspects of risk 

management are beyond the purview of the individual risk analyst—these 

decisions are carried out by decision-makers that are not involved in the risk 

assessment stage of PRA. 

The analytical aspect of risk management is the component that considers and 

weighs various options for mitigating risk. Options are usually analyzed for 

efficacy and feasibility, and to some extent costs associated with various 

options. The analysis of options in pest risk management necessitates a close 

linkage with the pest risk assessment part of PRA. The risk assessment should 
Conducting Pest Risk Assessment in PPQ

Risk Management in pest risk analysis

2-65 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

provide relevant information and analysis regarding a particular pathway(s), 

control points, uncertainties identified in the assessment, pests likely to be in a 

pathway, and important information about the biology of the pest that may 

factor into the selection of risk management options (e.g., feeding strategies, 

host status, etc.). Risk management is therefore dependent on the risk 

assessment to provide information about what mitigation options may be 

useful, and how various mitigation options will affect overall risk. 

The operational aspect of risk management is the selection and application of 

mitigation options that are decided upon based on the policy and analytical 

components of pest risk management. For imported commodities, this may be 

the designation of a specific work plan between trading partners, or the 

implementation of a preclearance program. Work plans will outline the 

activities that must be undertaken for the commodity to be imported (e.g., 

specified areas for export, packing conditions, treatments, etc.). Depending on 

the commodity, the pests and the level of risk involved, the operational 

component may be fairly simple (a single phytosanitary treatment like 

fumigation) to highly complex (a large-scale systems approach for managing 

several pests). 

The IPPC has produced several standards that provide general guidance on 

pest risk management, as well as some standards that provide specific guidance 

on particular aspects of pest risk management—for instance, standards that 

address pest-free areas, specific pests like fruit flies or specific types of 

phytosanitary treatments. The ISPMs particularly relevant to pest risk 

management, and which may be consulted in identifying options, are shown in 

Table 2-2.
Conducting Pest Risk Assessment in PPQ

Uncertainty in risk management

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-66

Uncertainty in risk management

The primary purpose for identifying and communicating uncertainty is to 

provide the decision maker with as complete and objective a view of the risk as 

possible. Carefully noting and considering uncertainty in PRA also helps 

governments to identify priority research needs and highlights for trading 

partners the points where the provision of more or better information may 

improve a decision. The uncertainty noted in the assessments of economic 

consequences and likelihood of introduction should also be considered and 

included in the analysis of risk management options. 

Where there is significant uncertainty, a conservative approach may be adopted 

as a temporary measure. However, the measures selected must nevertheless be 

based on a risk assessment that takes into account the available scientific 

information. In these circumstances the measures should be accepted as 

provisional and reviewed as soon as additional information becomes available.

The overall approach to dealing with uncertainty is addressed as a policy 

question, but it is the responsibility of the risk analyst to highlight uncertainty 

in the analysis and the potential effects of uncertainty during the risk 

management stage. 

Table 2-2. ISPMs with special relevance for pest risk management.

ISPM No. Title

1 Phytosanitary principles for the protection of plants and the application 

of phytosanitary measures in international trade

4 Requirements for the establishment of pest free areas

10 Requirements for the establishment of pest free places of production 

and pest free production sites

14 The use of integrated measures in a systems approach for pest risk 

management

18 Guidelines for the use of irradiation as a phytosanitary measure

22 Requirements for the establishment of areas of low pest prevalence

23 Guidelines for inspection

24 Guidelines for the determination and recognition of equivalence of phytosanitary measures

26 Establishment of pest free areas for fruit flies (Tephritidae)

28 Phytosanitary treatments for regulated pests

29 Recognition of pest free areas and areas of low pest prevalence

30 Establishment of areas of low pest prevalence for fruit flies (Tephritidae)

32 Categorization of commodities according to their pest risk
Conducting Pest Risk Assessment in PPQ

Process 10: Risk mitigation notes

2-67 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Process 10: Risk mitigation notes

In APHIS-PPQ, the processes of risk assessment and risk management for 

commodity imports are conducted separately and by two different groups 

within PPQ. Although individual risk analysts are not ultimately involved in 

developing the risk management for document for commodity imports, the 

analyst(s) that conducts the assessment is in the best position to provide 

analytical information that will inform the decisions being made about risk 

management. This information is placed in an internal document called “risk 

mitigation notes” to be shared with the risk managers to ensure that important 

information that would be of potential use in risk management is not lost. 

Preparing the risk mitigation notes is an informal process that will vary from 

analysis to analysis, but general guidance is on preparing this document is 

provided here. 

Guidance for preparing risk mitigation notes

Step 1: Identify possible options

General options. Traditionally, measures applied to imported commodities 

have relied on high-efficacy (e.g., probit-9 mortality) phytosanitary treatments 

aimed at reducing the presence of a particular pest (e.g., a species of fruit fly) 

on a given commodity. For example, phytosanitary treatments may include 

fumigations, cold treatments, heat treatments, or irradiation. However, a wide 

array of measures may be applied to mitigate risk (either singly or in 

combination), in addition to traditional phytosanitary treatments. The measures 

listed below are examples of those that are most commonly applied to traded 

commodities. The available measures can be classified into broad categories. 

These include measures (ISPM No. 11: IPPC, 2004a): 

applied to the commodity post-harvest (e.g., brushing, washing, waxing, 

treatments), 

applied to prevent or reduce original infestation of the commodity by a 

pest(s) (e.g., integrated pest management (IPM) programs, bagging, 

safeguarding, sanitation, etc.), 

applied to ensure the area or place of production of the consignment is 

free from the hazard (e.g. pest free areas or areas of low pest prevalence), 

and

concerning the prohibition of commodities (in the absence of any other 

feasible options). 
Conducting Pest Risk Assessment in PPQ

Process 10: Risk mitigation notes

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-68

Specific options. In Table 2-3, we summarize many of the risk management 

options commonly applied pre- and post-harvest to commodities to reduce, 

prevent or eliminate quarantine pests (IPPC, 2002). In some cases, a single 

measure may be sufficient to manage risk (e.g., a high mortality treatment); 

however, in many cases, additional measures are needed to reduce risk to an 

acceptable level. 

Table 2-3. Measures that can be applied to manage pest risk^ (IPPC, 2002; Jang and 

Moffit, 1994).

Pre-harvest Pest-free areas or areas of low pest prevalence 

Resistant cultivars

Healthy planting material

Pest mating or development disruption

Sanitation and cultural controls

Certification schemes

Testing

Protected conditions*

Harvest Harvesting at specific times or specific stages of ripeness

Culling infested products

Field sanitation 

Harvest technique

In-field chemical treatments

Field surveillance

Tarping*

Sanitation*

Post-harvest handling Post-harvest treatments (chemical, heat, waxing, washing 

brushing, etc.)

Testing

Culling

Packinghouse inspection

Processing (degree and type)

Method of packing*

Screening*

Sanitation*

Shipping Treatment in transit (e.g., cold treatment)

Speed and type of transport

Pre-shipment inspection

Testing

Sanitation*

Type of packaging*
Conducting Pest Risk Assessment in PPQ

Process 10: Risk mitigation notes

2-69 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Systems approaches and control points. “Systems approach” is defined as “the 

integration of different risk management measures, at least two of which act 

independently, and which cumulatively achieve the appropriate level of 

protection against regulated pests” (IPPC, 2012). Systems approaches may be 

applied in cases where a single measure, such as a phytosanitary treatment, is 

either not available or is not likely to achieve the appropriate level of 

phytosanitary protection or in cases where the only other alternative is 

prohibition. The cumulative effect of combining independent measures can 

provide the necessary level of phytosanitary protection where no other 

alternatives are available.

Systems approaches include independent measures, redundancy, and 

safeguarding. Combining measures that act independently of each other has the 

advantage that if any one measure fails, the overall system maintains a high 

level of efficacy. Similarly, including redundant (or overlapping) measures 

means that if one measure applied at a particular point in the production chain 

fails, another measure directed at that same point will assure that mitigation of 

risk still occurs. Lastly, measures that do not necessarily reduce pest 

prevalence, but that are aimed at preventing any new risk from being 

introduced into the system are called “safeguards” (IPPC, 1999; Follett and 

Neven, 2006). 

The types of measures that are applied in a systems approach can occur 

anywhere in a production chain, from pre-planting and pre-harvest through 

distribution and final end-use of the commodity (Table 2-3). Thus, the main 

advantage of systems approaches is that the risk is managed beginning at 

origin, thereby reducing the level of risk for the importing country. Systems 

approaches can also be used to mitigate the risk of pests that are not normally 

Distribution Restrictions on ports of entry

Restrictions on time of year

Post-entry quarantine

Post-entry Inspection

Post-entry treatment

Packaging*

End use Restrictions on end-use

Post entry processing

Packaging*

*Indicates a safeguarding measure (see section on Systems Approaches).

^This table is not inclusive of all potential measures; it lists the most common measures used 

on imported commodities.

Table 2-3. Measures that can be applied to manage pest risk^ (IPPC, 2002; Jang and 

Moffit, 1994).
Conducting Pest Risk Assessment in PPQ

Process 10: Risk mitigation notes

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-70

associated with the commodity (hitchhikers or contaminating pests), or pests 

that are not accounted for in the PRA process (unknown pests) (MAF, 2008).

In general, the use of a systems approach requires a relatively good knowledge 

of the production practices, the biology of the pest(s), and its relationship to the 

host(s) and post-harvest practices. In many cases, a systems approach can be 

highly flexible in the number and type of measures applied (as long as at least 

two measures act independently), even if specific data on efficacy is lacking. 

The number and types of measures combined in a systems approaches can 

range from very simple combinations (e.g., two independent measures such as 

low pest prevalence combined with fumigation) to highly complex, “control 

point” systems (IPPC, 1999; IPPC, 2002). This is dependent on the 

level of risk involved; 

cost, feasibility, and efficacy of possible measures;

suitability of any given management option for managing that risk; 

availability of information for the pest(s) and associated commodity; 

the level of uncertainty; and

the appropriate level of protection (or acceptable level of risk).

The role of control points in risk management and systems approaches. For 

the purposes of this discussion, it is useful to make a distinction between 

“control points” and “critical control points.” Control points are points where 

controls can be applied in the production chain, and the controls are expected 

to have some effect on the system (i.e., a reduction in risk). We may or may not 

be able to measure the exact effect of the control, but we would expect that the 

control would have some (perhaps undefined) level of efficacy. An example of 

a control point that may be difficult to measure would be field sanitation and 

the removal of fallen fruit from orchards to manage risks associated with fruit 

flies. We know that sanitation would reduce risk, but the exact level of efficacy 

would be difficult to measure. In addition, certain measures or conditions exist 

or are included to compensate for uncertainty. These may not be monitored as 

independent procedures (e.g., packinghouse sorting), or may be monitored but 

not controlled (e.g., host preference/susceptibility).

In other cases, the control points may be well defined, and the level of efficacy 

of that control can be measured, quantified, monitored, and verified. In 

addition, such points in the system may be points where controls must be 

applied in order to reduce risk sufficiently. These would be regarded as critical 

control points. For some commodities, most or all of the specific points in the 

production chain can be well defined, the hazards and mitigations can be 

measured, each point can be controlled, and the efficacy of each mitigation 
Conducting Pest Risk Assessment in PPQ

Process 10: Risk mitigation notes

2-71 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

step can be verified and documented. In these cases, a “critical control point” 

system can be applied—this being the most rigid type of systems approach 

used for phytosanitary risk management (IPPC, 1999).

The use of a control point system for phytosanitary purposes does not imply or 

prescribe that application of controls is necessary to all control points. These 

are addressed by risk management procedures whose contribution to the 

efficacy of the system can be measured and controlled. 

Even if a critical control point system is not used in risk management, the 

analysis of control points and critical control points may be useful to identify 

and analyze hazards as well as the points in a pathway where risks can be 

reduced and monitored and adjustments made where necessary. 

Step 2: Identify information and option for risk management

The risk analyst is uniquely positioned to provide relevant information for the 

formulation of risk management options and plans. Throughout the analysis, 

the risk analyst should have documented information relevant to risk 

management for 

quarantine pests likely to follow the pathway, 

the pathway itself (see Process 3: Defining the pathway on page 2-6) and 

potential control points (and critical control points),

potential effects of mitigations, and 

any uncertainty associated with the pest(s) and the pathway.

Table 2-4 and Table 2-5 provide examples of how and what type of 

information can be presented on both the pathway and the pests. It includes 

information on the pathway (described in the risk assessment) and information 

on pests gathered during the analysis that is particularly relevant to risk 

management. Figure 2-6 and Figure 2-7 are examples of a completed template 

using the fruit fly Dacus ciliates (pest) on Jordan beans (pathway).

Information presented to the risk manager should highlight potential 

mitigations for the pest(s) and the pathway, the anticipated effects of 

mitigations, and the level and source of uncertainty (if applicable). Note that 

analyzing the pathway for specific control points, as highlighted in the 

previous section may assist the analyst in determining whether mitigations 

applied at control points will have a significant effect on the overall risk (e.g., 

critical control points). The information provided to the risk manager should 

include particularly critical details from the analysis (including relevant 
Conducting Pest Risk Assessment in PPQ

Process 10: Risk mitigation notes

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-72

uncertainty) that will aid in decision-making and in the determination of which 

measures will be most effective, feasible and justified.

Table 2-4. Examples of the type of pathway information useful for risk managers.

Information relevant to risk mitigation

Potential mitigationsAnticipated effect 

or impact

Uncertainty (level 

and source)

Pathway/commodity: include information on pathway/commodity/processing relevant to risk 

management. Information may come from exporting country or from technical sources.

Production areas Protected cultivation, pest-free areas, 

or areas of low pest 

prevalence

Prevention of infestationLack of specific data

Conflicting data

Variable data

Variability of commodity 

Availability of technology

Suitability of technology

Effects on or of commodity

Need for monitoring

Efficacy of inspection

Unintended use

Volumes may not be 

tracked

Planting and harvest timesPest-free time periods/reduced host 

susceptibility

Reduce or prevent 

infestation

Cultivar selection Host status/resistanceReduce or prevent 

infestation

Post-harvest handlingWashing, waxing, 

brushing, bathing, 

culling, etc.

Reduce or prevent 

infestation

Processing Peeling, baling, 

heating, cooling, 

cooking, milling, etc.

Reduce or prevent 

infestation

Packing and safeguardingPrevention of reinfestationPrevention of reinfestation

Treatments Commodity tolerates 

various treatments

High mortality

Shipment Mode of shipments 

includes treatment 

potential (e.g., cold 

treat in transit)

Potential mortality

Inspection Commodity is easily 

inspect/tested

Detect infestation

Intended use Devitalization Prevent establishment

Volume of exports** 

(proposed by exporting country)

Note whether or not 

increased volumes 

beyond originally 

requested volume 

will affect overall risk

Potentially increase 

risk**
Conducting Pest Risk Assessment in PPQ

Process 10: Risk mitigation notes

2-73 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Table 2-5. Examples of the type of pest information useful for risk managers.

Information relevant to risk mitigation

Potential mitigationsAnticipated effect 

or impact

Uncertainty (level 

and source)

Pest: include a section for each actionable pest or group pests as appropriate

Pest biology (feeding, reproduction, 

development)

In-field pest management practicesReduce or prevent 

infestation

Lack of specific data

Conflicting data

Variable data

Variability of pest 

(e.g., biotype or 

strain differences)

Availability of technology

Suitability of technology

Use of proxy species for treatments

Efficacy of detection

Unknown organisms

Seasonality Time of harvest or 

shipping (e.g., when 

the pest is not 

active)

Reduce or prevent 

infestation

Host specificity Resistant cultivars, 

non-host status

Reduce or prevent 

infestation

Susceptibility (or 

resistance) to treatments

Pre-shipment, intransit, or post-entry 

treatments

Reduce or eliminate 

infestation

Distribution (geographic, temporal)Restrictions on time 

of year or destinations of imports

Prevent establishment

Climate suitability Restrictions on time 

of year or destinations of imports

Prevent establishment

Environmental resistance or susceptibilityVarious types of 

shipping conditions 

or post-harvest handling

Reduce infestation

Detectable/testable Field trapping, reliability of pre- or 

post-entry inspection

Detect infestation

Presence of hitchhikersInspection Detect infestation

Role of vectors Determine presence or absence of 

vectors in the United 

States by surveillance

Reduce establishment
Conducting Pest Risk Assessment in PPQ

Process 10: Risk mitigation notes

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-74

Table 2-6. Example reporting for the pathway/commodity combination of Jordan bean.

Relevant section of risk 

assessment

Information 

relevant to 

risk mitigation

Potential mitigation Anticipated effect 

or efficacy

Uncertainty (level 

and source)

Scope, Risk 

Element A1

Production 

areas

Field management of pests in that 

country usually implements IPM programs, which includes biological control.

Some reduction in 

pest prevalence, 

particularly external 

feeders.

Medium high 

uncertainty, since 

specific controls 

are not listed.

Scope, Risk 

Element A1

Planting and 

harvest times

n/a n/a n/a

Scope, Risk 

Element A1

Cultivar selectionn/a n/a n/a

Scope, Risk 

Element A2

Post-harvest 

handling

Beans need to be intact, fresh 

appearance, clean (in particular free 

from any impurity or any visible chemical trace), free from foreign smell or 

taste, free from all abnormal external 

moisture, and sufficient size. The 

state of the product must be such as 

to enable it to withstand transport and 

handling. 

Some removal of 

external pests; 

anticipate a 

medium level of 

efficacy for this 

measure, but it 

would be insufficient alone. 

Medium high certainty that this measure is effective for 

removing most 

external pests.

Scope, Risk 

Element A2

Processing n/a n/a n/a

Scope, Risk 

Element A2

Packing and 

safeguarding

Standard packinghouse procedures: 

1) The contents of each package 

must be uniform and contain only 

beans of the same origin, variety, and 

quality. 2) Packaging must be of such 

a kind as to ensure that the beans are 

properly protected; any paper or other 

material used inside the package 

must be new and harmless to human 

food; and when printed matter is used 

the printing must be on the outside 

only so as not to come into contact 

with the product.

Each package must be legibly and 

indelibly marked on the outside with 

data for 1) Packer and dispatcher 

identification: name, address or code 

mark; 2) Nature of the product 

description: type (fresh beans, runner beans, and fine beans) or variety; 

3) Product origin: district or national, 

regional or local, and trader name; 4) 

Commercial specification description: class, sizing, and classification; 

and 5) Official control mark.

Protection against 

re-infestation postpackaging—generally highly effective at preventing 

an increase in risk.

Medium high certainty that this measure is effective for 

preventing re-infestation by pests.

Scope, Risk 

Element A3

Shipment n/a n/a n/a
Conducting Pest Risk Assessment in PPQ

Process 10: Risk mitigation notes

2-75 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Scope, Risk 

Element B2

Import timing n/a n/a n/a

Scope Treatments n/a n/a n/a

Scope Intended use Beans are intended for consumption. 

It is possible, however, that beans 

could be used for planting.

Low increase in 

risk possible if 

beans were to be 

planted and are 

viable.

High uncertainty—

data to support or 

refute potential risk 

are not available.

Scope Volume of 

exports**

n/a n/a n/a

Variable Inspection n/a n/a n/a

Variable Other n/a n/a n/a

Table 2-6. Example reporting for the pathway/commodity combination of Jordan bean.

Relevant section of risk 

assessment

Information 

relevant to 

risk mitigation

Potential mitigation Anticipated effect 

or efficacy

Uncertainty (level 

and source)

Table 2-7. Example reporting for the pest Dacus ciliates (Tephritidae).

Relevant section of risk 

assessment

Information 

relevant to 

risk mitigation

Potential mitigation Anticipated effect 

or efficacy

Uncertainty (level 

and source)

Risk Elements 

A1, A2, A3

Pest biology n/a n/a n/a

Risk Elements 

A1, A2, A3, B2

Seasonality **See climate suitability. n/a n/a

Risk Element 

A1

Host specificity This species of fruit fly is primarily 

associated with cucurbits. Beans may 

only be a conditional host for this species—i.e., given high population pressure and proximity to cucurbit hosts. 

This may reduce the prevalence of 

the pest in the commodity. 

Reduced prevalence of the pest in 

the commodity—in 

combination with a 

treatment, low 

prevalence is likely 

to be sufficient to 

manage risk for this 

pest.

Medium low—

further 

information on 

host status (e.g., 

experimental 

and field data 

on whether 

beans are a 

natural host for 

this species 

would reduce 

uncertainty.
Conducting Pest Risk Assessment in PPQ

Process 10: Risk mitigation notes

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 2-76

Risk Element 

B1

Distribution In combination with host status, the 

prevalence of this pest may be low in 

commercial bean production 

(depending on proximity to other host 

material and other environmental 

conditions). Surveillance records may 

inform as to whether this pest is present in sufficient numbers to present a 

risk in commercially produced beans.

Surveillance to 

demonstrate the 

prevalence of the 

pest will not reduce 

risk in itself but will 

provide supporting 

evidence in making determinations 

of host status (e.g., 

conditional host 

status) and will 

indicate if the population is low 

enough to be effectively treated with 

treatments such as 

cold treatment. 

n/a

Risk Element 

B2

Climate suitabilityImportation of beans from Jordan during winter months would reduce survivability of this pest if infested beans 

were imported. 

Reduce likelihood 

of establishment 

since this species 

is a subtropical 

pest. 

Medium low.

Risk Elements 

B1, B2

Environmental 

resistance or 

susceptibility

n/a n/a n/a

Scope Presence of 

hitchhikers

n/a n/a n/a

Variable Detectable/

testable

n/a n/a n/a

Variable Susceptibility 

or resistance 

to treatments

Fruit flies in the family Tephritidae are 

susceptible to many types of treatments including cold treatment and 

irradiation. In combination with conditional host status, a treatment would 

be sufficient to manage risk associated with this pest.

Reduce risk to an 

acceptable level for 

this pest. 

Medium low uncertainty--specific 

treatments for this 

pest may not exist, 

in which case proxy 

treatments may be 

necessary.

Variable Role of vectors n/a n/a n/a

Variable Other n/a n/a n/a

Table 2-7. Example reporting for the pest Dacus ciliates (Tephritidae).

Relevant section of risk 

assessment

Information 

relevant to 

risk mitigation

Potential mitigation Anticipated effect 

or efficacy

Uncertainty (level 

and source)
08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-1

Section

3 Supplements and 

References

Supplement 1: WTO Disputes

The SPS Agreement contains provisions for settling disputes between 

Members in cases where Members contend that another’s measures are not 

consistent with the Agreement. To date, there have been six dispute settlement 

cases related to the SPS Agreement, and in each case, risk analysis has played 

a prominent role. The cases are:

The Variety Testing Case (the United States vs. Japan)

The Hormones Case (the United States and Canada vs. the European 

Communities)

The Salmon Case (Canada vs. Australia)

The Fire Blight Dispute (the United States vs. Japan)

The Fire Blight Dispute (New Zealand vs. Australia)
Supplements and References

Supplement 1: WTO Disputes

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-2

The GMOs Case (the United States and Canada vs. the European 

Communities)

This section provides a brief summary of five of those cases, including a 

description of key SPS principles relevant to each case. 

The Variety Testing Case (the United States vs. Japan)

Measure at issue. Japan’s requirement to test each variety of certain agricultural products (apples, cherries, 

peaches, walnuts, apricots, pears, plums, and quinces) for the efficacy of treatment against codling moths. The United 

States claimed that it was not necessary to test each variety of a fruit for the efficacy of the treatment.

In this case, the issue of scientific justification was the key SPS principle being tested. Members have two options to 

show that their measures are based on science. They may either:

 base their measures on international standards or 

 base their measures on scientific risk assessment. 

Panel findings. The variety testing requirement violated Article 2.2 since there was no rational relationship between 

the scientific evidence submitted by Japan and the measure.

The exception provided in Article 5.7 did not apply. Japan invoked this article, which allows Members to take provisional 

measures where scientific information is insufficient. However, the Panel found no evidence that Japan had actively 

sought to obtain additional information in order to review its measure within a reasonable period of time, as required by 

Article 5.7.

The variety testing requirement violated Article 5.6 since it was more trade-restrictive than required to achieve Japan’s 

appropriate level of protection. The Panel was unable to rule on product-by-product testing, an alternative proposed by 

the United States, since it did not have sufficient evidence to decide whether this method achieved Japan’s appropriate 

level of protection. But the Panel considered another testing method related to sorption levels as a less trade-restrictive 

alternative.

The measure violated Article 7 and Annex B. The Panel found the variety testing requirement should have been published although the requirement was not mandatory.

Appellate body findings. Upheld the Panel’s finding on Article 2.2 that the measure was not based on science.

Upheld the Panel’s finding on Article 5.7, and noted that the length of the “reasonable period of time” had to be established on a case-by-case basis.

Reversed the Panel’s finding on Article 5.6 regarding determination of sorption levels. The alternative measure had not 

been proposed by the United States, which had the burden of proof.

Upheld the Panel’s finding on Article 7 and Annex B, agreeing that the measure should have been published.
Supplements and References

Supplement 1: WTO Disputes

3-3 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

The Hormones Case (the United States and Canada vs. the European Communities)

Measure at issue. An EC (European Communities) ban on imports of beef from cows treated with hormones [oestradiol 17ß, progesterone and testosterone, trenbolone acetate (TBA), zeranol, and melengestrol acetate] for growth-promotion purposes. The EC claimed the ban was necessary for food safety; the United States and Canada claimed there 

was no evidence of harm to human health. 

In this case, the key principles being tested were “harmonization” (basing measures on international standards) and/or 

technically justifying measures which deviate from standards (through risk assessment).

It is important to note that the encouragement to use international standards does not mean that these constitute a floor 

or a ceiling on national standards. National measures do not violate the SPS Agreement simply because they differ from 

international norms. According to Article 3 and Article 5 of the SPS Agreement, Members are permitted to adopt SPS 

measures that are more stringent than the relevant international standards or adopt SPS measures when international 

standards do not exist, provided the measures are

 based on scientific risk assessment, 

 consistently applied, and 

 not more trade restrictive than necessary. 

Panel findings. The EC measure violated Article 3 on harmonization. Although international standards existed for five 

of the six hormones in question, the EC measure was not based on these standards; it reflected a higher level of protection and was not justified by a risk assessment, as required by Article 3.3.

The EC ban was not based on a risk assessment, and violated Article 5.1. The EC’s scientific studies on five of the hormones did not support the ban on hormone-treated meat.

The EC measure violated Article 5.5, because the level of protection sought for hormone-treated meat was higher than 

required in comparable situations; these differences were arbitrary or unjustifiable, and resulted in discrimination or a 

disguised restriction on trade. In particular, in contrast to the ban on hormones for growth-promoting purposes, the EC 

permitted higher levels of the same naturally occurring hormones in untreated meat and other foods; the use of the 

same hormones for therapeutic and herd management purposes; and the use of other growth promoters (such as the 

anti-microbial carbadox and olaquindox, known to be carcinogenic) in swine production.

The EC had not invoked Article 5.7, which allows precautionary measures to be taken on a provisional basis, but rather 

the “precautionary principle” in general. The Panel found that invoking the “precautionary principle” did not override a 

country’s obligations under the SPS Agreement.

Appellate body findings. Agreed with the Panel’s finding that since the EC measure reflected a higher level of protection than the international standard and was not justified by a risk assessment, it violated Article 3.

Confirmed the Panel’s finding on Article 5.1 that there was no rational relationship between the measure and the scientific evidence submitted on five of the hormones, and found that there was no risk assessment at all for the sixth hormone (melengestrol acetate).

Reversed the Panel’s findings on Article 5.5. The Appellate Body considered that there was a fundamental difference 

between added hormones and naturally-occurring hormones in meat and other foods, and that the therapeutic use of 

hormones involved closer supervision and control. Although the Appellate Body agreed that the difference between a 

ban on hormone-treated beef and the use of growth promoters in swine production was arbitrary, it did not consider that 

this resulted in discrimination or a disguised restriction on trade.

Upheld the Panel’s finding on the use of precaution and its relationship with Article 5.7.

Implementation/“retaliation”. When the EC was unable to implement by the May 13, 1999 deadline, the United 

States and Canada sought the right to retaliate against the EC in the amount of US$202 million per year and CDN$75 

million per year. The arbitrators found the appropriate level to be US$116 million and CDN$11.3 million per year, respectively.
Supplements and References

Supplement 1: WTO Disputes

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-4

The Salmon Case (Canada vs. Australia)

Measure at issue. Australia’s ban on importation of fresh chilled or frozen salmon, allegedly to protect the domestic 

salmon population from a number of diseases. Canada claimed that salmon imported for human consumption was very 

unlikely to lead to the introduction of these diseases.

In this case, the key principles being tested were “harmonization” (basing measures on international standards) and or 

technically justifying measures which deviate from standards (through risk assessment).

Panel findings. The import ban violated Article 5.1, because it was not based on a risk assessment. Australia had 

carried out a risk assessment for ocean-caught Pacific salmon, but the Panel found no rational relationship between the 

measure and the risk assessment. For the other types of salmon, no risk assessment had been carried out. The Panel 

considered that the measure prohibiting imports of fresh chilled and frozen salmon could also be described as a requirement that the salmon be heat-treated.

The Australian measure violated Article 5.5, because the level of protection sought for salmon was much higher than in 

comparable situations; these differences were arbitrary or unjustifiable, and resulted in discrimination or a disguised 

restriction on trade. In particular, there were no restrictions on imports of frozen herring for bait; and there were few 

restrictions on imports of live ornamental fish.

The ban on salmon was more trade-restrictive than required to achieve Australia’s appropriate level of protection, and 

therefore violated Article 5.6.

Appellate body findings. Reversed the Panel’s finding that the ban on the other types of salmon was not based on 

a risk assessment, because the Panel made the finding based on the heat-treatment requirement. It found, however, 

that Australia’s risk assessment on ocean-caught Pacific salmon was not a proper risk assessment in the sense of the 

SPS Agreement, and the ban therefore violated Article 5.1. It upheld the finding that no risk assessment had been carried out for other types of salmon.

Upheld the Panel’s finding on Article 5.5, that the higher level of protection on salmon resulted in discrimination or a disguised restriction on international trade.

Reversed the Panel’s findings on Article 5.6 because it was based on the heat-treatment requirement, and not on the 

import ban.

Article 21.5 (Compliance) Panel findings. Australia had failed to comply by the deadline set by the arbitrator 

because its new measure on salmon took effect on July 19, 1999, and new measures on other fish (to comply with the 

consistency requirement) were phased in at later dates.

The requirement that salmon be in a particular consumer-ready form was not based on a risk assessment, and violated 

Article 5.1.

The definition of consumer-ready product was more trade-restrictive than required, and thus violated Article 5.6.
Supplements and References

Supplement 1: WTO Disputes

3-5 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

The Fire Blight Dispute (the United States vs. Japan)

Measure at issue. Japan's set of requirements on apples from the United States, including that they come from an 

orchard free of fire blight, surrounded by a buffer zone, undergo at least three annual inspections, chlorine treatment, 

etc. in order to prevent the entry of Erwinia amylovora, the bacteria that causes fire blight, into Japan. The United States 

claimed that there was no evidence that mature, symptomless apples could serve as a pathway for the disease. 

In this case, the key principles being tested were “harmonization” (basing measures on international standards) and or 

technically justifying measures which deviate from standards (through risk assessment).

Panel findings. Japan's measure, the set of requirements taken as a whole, violated Article 2.2 because it was maintained without sufficient scientific evidence that apple fruit could serve as a pathway for the entry, establishment or 

spread of fire blight. The Panel considered the risk from mature, symptomless apples, the U.S. export product, and the 

risk that something other than mature, symptomless apples might be inadvertently or illegally shipped. 

The exception provided in Article 5.7 did not apply. This was not a situation in which sufficient scientific evidence did not 

exist, rather, there was a wealth of scientific evidence regarding fire blight but it did not support Japan's measure.

Japan's measure violated Article 5.1 because it was not based on a risk assessment appropriate to the circumstances. 

Japan's pest risk assessment was not sufficiently specific regarding the risks of entry, spread or establishment through 

imported apples as opposed to other possible pathways, nor did the risk assessment evaluate the likelihood of entry, 

establishment or spread through apples. Furthermore, Japan's risk assessment failed to evaluate the risk according to 

the SPS measures which might be applied, but rather considered only the existing measures.

The Panel exercised judicial economy and did not rule on an alleged claim that the measure was more trade restrictive 

than necessary in violation of Article 5.6. The Panel found that the United States had failed to make a prima facie argument that the measure had not been notified and was in violation of Article 7 and Annex B.

Appellate body findings. The Appellate Body upheld the Panel's findings with respect to violations of Article 2.2 and 

5.1, as well as with regard to the inapplicability of Article 5.7 in this situation. The Panel's findings on Article 7 and Annex 

B were not appealed. 

In addition, the Appellate Body ruled that the Panel had the authority to make findings and draw conclusions with 

respect to all apple fruit from the United States, and not just with respect to mature, symptomless apples as the United 

States claimed.

The Appellate Body furthermore rejected an argument that the Panel had failed to objectively assess the evidence 

before it regarding the likelihood of completion of the last stage of the pathway. 

Article 21.5 (Compliance) Panel findings. Japan breached Article 2.2 of the SPS Agreement by maintaining the 

compliance measure at issue without sufficient scientific evidence.

Japan violated Article 5.1 of the SPS Agreement because the phytosanitary measure was not “based on an assessment, as appropriate to the circumstances, of the risk to [...] plant life or health” in Japan because Japan relied on uncorroborated new studies that do not support the conclusion that imported apples could spread fire blight.

If the United States only exported mature, symptomless apples, the alternative measure proposed by the United States 

would meet the requirements of Article 5.6 as a substitute to Japan's current measure. 
Supplements and References

Supplement 1: WTO Disputes

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-6

The GMOs Case (the United States and Canada vs. the European Communities)

Measure at issue. Alleged general EC moratorium on approvals of biotech products, EC measures allegedly affecting the approval of specific biotech products, and EC member State safeguard measures prohibiting the import/marketing of specific biotech products within the territories of these member States.

In this case, the issues of scientific justification, transparency, equivalence, and approval procedures were the key SPS 

principles being tested. 

In 2003, the United States requested the establishment of a Panel to examine the EC’s 1998 alleged moratorium on the 

approval of biotech products, which the United States claimed was restricting trade on food and agricultural products 

and was inconsistent with the SPS Agreement’s Articles 2, 5, 7, and 8. The United States alleged that there existed a 

moratorium on the approval of biotech products, which since 1998 had limited the number of products receiving 

approval in EC states. Additionally, so-called “safeguard measures” were in place in six EC Member states, prohibiting 

certain biotech products that had already been approved at the EC level. 

General EC moratorium. The Panel found that a general de facto moratorium on approvals of biotech products was 

in effect on the date of panel establishment, i.e., August 2003. It was general in that it applied to all applications for 

approval pending in August 2003 under the relevant EC legislation, and de facto because it had not been formally 

adopted. Approvals were prevented through actions/omissions by a group of five EC member States and/or the European Commission.

SPS Articles 5.1 and 2.2: The Panel found that the EC decision to apply a general moratorium was a decision concerning the application/operation of approval procedures, i.e., a procedural decision to delay final substantive approval decisions. It was not applied for achieving the EC level of sanitary or phytosanitary protection and, hence, was not an “SPS 

measure” subject to Articles 5.1 or 2.2. 

SPS Annex C(1)(a) and Article 8: The Panel found that the general moratorium led to undue delay in the completion of 

the EC approval procedure conducted in respect of at least one biotech product at issue and thereby to the European 

Communities acting inconsistently with Annex C(1)(a) and, by implication, Article 8.

Product-specific measures. SPS Annex C(1)(a) and Article 8: The Panel found that in 24 of the 27 product-specific 

approval procedures it examined, the procedure had not been completed without undue delay. In respect of these procedures, the European Communities had, therefore, acted inconsistently with Annex C(1)(a) and, by implication, Article 

8.

EC Member State safeguard measures. SPS Article 5.1, 2.2 and 5.7: According to the Panel, the record did not indicate that there was insufficient evidence to conduct a risk assessment within the meaning of Article 5.1 and Annex A(4) 

for the biotech products subject to safeguard measures. As a result, Arts. 5.1 and 2.2 were applicable. In this regard, the 

Panel found that none of the safeguard measures at issue were based on a risk assessment as required under Art. 5.1 

and defined in Annex A(4). By maintaining measures contrary to Article 5.1, the European Communities had, by implication, also acted inconsistently with Article 2.2.
Supplements and References

Supplement 1: WTO Disputes

3-7 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Figure 3-1. Relevant findings of SPS disputes.
Supplements and References

Supplement 2: Plant Hardiness Zones Area and Population Analysis

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-8

Supplement 2: Plant Hardiness Zones Area and Population Analysis

Plant hardiness zones represent areas of average annual minimum 

temperatures, illustrating where it is safe to plant plants without frequent cold 

damage. They are a component of phytosanitary risk analysis and are a useful 

tool for estimating potential area of impact for plant pests. Using Geographic 

Information Systems (GIS), it is possible to determine the approximate area 

and population of the United States covered by each hardiness zone, which 

allows for a more accurate risk estimate. 

Global plant hardiness zones were created by ZedX Inc. for the North Carolina 

State University APHIS Plant Pest Forecast System (NAPPFAST) using 

methods described in Magarey et al. (2008). The zones were created at a grid 

resolution of 10 km using monthly data from the Climate Research Unit (CRU) 

and station data from the Daily Global Historical Climatology Network 

(GHCN). Individual hardiness zone grid files for zones 1-13 were transferred 

into ArcInfo 9.2. The geo-tiff grid files were converted to polygons and the 

area in square miles was calculated using the edit and summarize function. To 

estimate population by hardiness zone, county data containing 2005 census 

data was utilized from the ESRI US County Area Shapefile. Counties were 

manually assigned to a hardiness zone when they were estimated to be covered 

by 50 percent or more of that zone. Population information from the assigned 

counties was obtained using the summarize function. Area was estimated for 

zones 12 and 13, which are present in Hawaii, but population for those zones 

was included in zone 11 using the previously described methodology. 

The plant hardiness zones for Puerto Rico, a commonwealth of the United 

States, were also analyzed using zone coverage of county areas to estimate 

area. Eight percent of the island was determined to be in Zone 11 and 92 

percent in Zone 12 (Figure 3-2). The population of Puerto Rico, estimated to 

be 3.944,249 in 2007, was obtained from the CIA World Factbook (CIA, 

2008). Area and population values for Puerto Rico were not included in the 

estimates for the United States. 

Table 3-1. Estimated percentage of area and population of the United States by plant hardiness zones. 

Hardiness zones were generated using data from 1997-2006 (Magarey et al., 2008); population 

estimates were derived from 2005 census data at county level.

Plant hardiness 

zone

Estimated area in 

square miles

Percentage of U.S. 

area

Population from 

2005 census

Percentage of U.S. 

population

1 199,053 5.6 94,942 0.03

2 130,616 3.7 15,490 0.01

3 206,116 5.8 1,172,840 0.04
Supplements and References

Supplement 2: Plant Hardiness Zones Area and Population Analysis

3-9 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Figure 3-2. Estimated percentage of area and population of the United States by plant hardiness zones. 

Hardiness zones were generated using data from 1997-2006 (Magarey et al., 2006); population 

estimates were derived from 2005 census data at county level.

Prepared by:

D. Borchert, Risk Analyst, USDA-APHIS-PPQ-CPHST-PERAL

R. Magarey, Senior Research Assistant, NCSU-CIPM

4 456,289 12.9 9,142,737 3.1

5 470,679 13.3 22,520,330 7.5

6 677,225 19.2 65,924,988 22.1

7 536,148 15.2 68,715,477 23.0

8 505,586 14.3 51,178,543 17.1

9 315,856 8.9 59,946,996 20.1

10 31,993 0.9 13,257,280 4.4

11 4,712 0.1 6,734,768 2.3

12 1,119 0.03 Included in 11 n/a

13 1,319 0.04 Included in 11 n/a

Totals 3,536,711 100 298,720,176 100

Table 3-1. Estimated percentage of area and population of the United States by plant hardiness zones. 

Hardiness zones were generated using data from 1997-2006 (Magarey et al., 2008); population 

estimates were derived from 2005 census data at county level.

Plant hardiness 

zone

Estimated area in 

square miles

Percentage of U.S. 

area

Population from 

2005 census

Percentage of U.S. 

population
Supplements and References

Supplement 3: Host Status

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-10

Supplement 3: Host Status

Host status issues in PRAs

Pests can be associated with host plants in different ways, depending on the 

biology of the host and pest, and the environment in which pests and hosts 

interact. The nature of the relationship that a pest has to a host can impact the 

ability of the host commodity to be a source of viable propagules of the pest 

that can lead to its entry and establishment in the PRA area. This supplement is 

meant to provide a conceptual framework for analyzing host status and a 

decision tool to evaluate not only host status as an intrinsic biological property 

of a pest as it interacts with a host, but also attempts to account in part for the 

likelihood of the pest to move on the commodity in a form and manner that 

would allow its introduction. Or more simply put, analysts are encouraged to 

look carefully at host status, and also determine whether or not the infested/

infected commodity will be a source of the pest, enabling it to become 

established. This guide attempts to increase the transparency of the process of 

evaluating host status for new risk analysts and our stakeholders, as well to 

improve the consistency of our risk assessments. 

Scope and purpose

Determining the status of hosts with respect to pests is one of the central pieces 

of information needed to conduct PRA. The determination of host status can 

have major impacts on phytosanitary measures required for importing and 

exporting commodities, as well as domestic level decisions and actions (e.g., 

eradication programs, surveys, etc.). In commodity- based PRAs (e.g., Q56 

PRAs for importation of fruits and vegetables for consumption), the issue of 

host status influences the PRA in four key places:

qualitative likelihood or probability the pest will follow the pathway for 

entry on the host,

qualitative likelihood or probability the pest will find suitable hosts after 

entry and establishment, 

qualitative likelihood or probability that the pest can spread, and 
Supplements and References

Supplement 3: Host Status

3-11 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

the extent of economic impact (on hosts in the importing country) that the 

pest is likely to have.

Because host status can affect the estimated level of risk for a pest (through the 

four likelihoods identified above), it is critical that host status be defined as 

accurately as possible in the PRA. 

There are many diverse sources of information available that provide lists of 

hosts for pests. Some of these sources simply associate the pest with a host(s) 

in a very general sense, while other sources of information provide a detailed 

description of the relationship of the pest to the host(s). Likewise, information 

sources may describe different types of hosts, according to the status of that 

host to the pest. This terminology is not harmonized and can be interpreted in 

many different ways. The diverse terminology and the diversity of descriptions 

of host- pest interactions may be extremely difficult to interpret when 

conducting PRA.

This paper provides guidelines for interpreting information regarding pesthost interactions for the purpose of PRA, and furthermore provides suggested 

terminology that should be used to describe the status of host(s) with respect to 

pests, or in defining the host-pest interactions. 

Key issues

Host status is, in many cases, very clear for well-documented pests for which 

there is agreement in the scientific literature. However, there can sometimes be 

considerable controversy in interpreting information, even for pests that are 

well understood. Host status requires regular review for several reasons:

errors in the literature or in databases and compendia (e.g. inaccuracy due 

to incorrect citations, incorrect interpretations). See Appendix A: 

Recommendation for Prunus persica varieties to be considered non-hosts 

for Bactrocera cucurbitae on page 3-27 for an example of this issue.

host status of a commodity may be variable depending on host and pest 

biology (e.g., imprecision due to changes in host status depending on 

season, ripeness, variety, geographic area, population density). See 

Appendix A: Recommendation for Prunus persica varieties to be 

considered non-hosts for Bactrocera cucurbitae on page 3-27 for 

examples.

host status is unclear (lack of data in the literature, conflicting 

information, or only experimental hosts are described but lacking field 

data). See Appendix A: Recommendation for Prunus persica varieties to 

be considered non-hosts for Bactrocera cucurbitae on page 3-27 for 

examples.
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Supplement 3: Host Status

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-12

cases where a pest is associated with a commodity but may not be feeding 

on that commodity (e.g., snails on tile, hitchhikers or contaminating pests; 

alfalfa weevil on pomegranate).

Terminology
Supplements and References

Supplement 3: Host Status

3-13 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Background

An array of terminology describes host-pest interactions in the scientific 

literature, but the terms are not used consistently nor are they harmonized and 

is difficult to interpret with regard to the level of risk the specified interaction 

may present. Examples of terms found in the literature include, but are not 

limited to, those found below.

These different terms imply information about the relationship of the pest to 

the host, and therefore, correspondingly, the level of risk associated with the 

host status but do not define the exact parameters for any of such relationship. 

For instance, terms such as natural, field, preferred, and primary host imply 

that the pest can be found on the host plant in the field (or other production 

system) and that the pest can survive and perpetuate itself under natural 

growing conditions for the host. Most work on host status has been done on 

fruit flies (Tephritidae), but host status concerns also occur with other groups 

of pests (including other arthropods and plant pathogens).

For example, ISPM No. 11 (IPPC, 2004a) talks about hosts that are capable of 

sustaining pests “under natural conditions.” This would not generally include 

laboratory or experimental hosts. Under certain conditions or circumstances, 

plants that are susceptible to a given pest in the laboratory may remain free 

from infestation or infection under natural conditions. Plants may be 

susceptible only at a certain life stage (fruiting, flowering, etc.) when the pest 

is not present and active. Physical features of the plant, such as hairs or wax 

layers, may prevent vectors or water droplets containing inoculum from 

contacting the plant surface. Experimental or laboratory inoculation or 

infestation methods can allow infestations or infections to occur that do not 

EXAMPLE host

field host

natural host

primary host

preferred host

commercial host

regulated host

reproductive host

conditional host

conditional non-host

experimental host

laboratory host

secondary host

non-preferred host

wild host

occasional host

minor host

poor host

rare host

natural non-host

non-host

host of unknown 

significance

alternate host

latent host

indicator host

local lesion host

diagnostic host

associated host
Supplements and References

Supplement 3: Host Status

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-14

occur in nature (e.g., mechanical inoculation, or dodder infection of a plant 

with a virus or phytoplasma normally vectored by an insect that does not feed 

on that plant; insect pests feeding on plants when lacking another food source).

National, regional, and international organizations have recognized the need to 

harmonize methods for determination of, and terminology related to, host 

status. This is important in conducting PRA, proposing risk mitigation options, 

communicating to domestic and foreign stakeholders, and in developing 

regulations and strategies to address pests. Two regional organizations (Asia 

Pacific Plant Protection Organization or APPPC, and North American Plant 

Protection Organization or NAPPO) have developed regional standards on host 

status, and the IPPC has a produced a draft standard on host status for fruit flies 

based largely on the two regional standards. The standards provide guidance to 

countries on how to determine host status, and further define categories of host 

status. 
Supplements and References

Supplement 3: Host Status

3-15 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Recommendation 1: Host status terminology

Consistent with the NAPPO RSPM No. 30 [Guidelines for the Determination 

and Designation of Host Status of a Fruit or Vegetable for Fruit Flies (Diptera: 

Tephritidae)] (NAPPO, 2008), the following terms should be used for hosts 

with regard to pests that feed on or infect hosts.

For the purposes of this document, a Type 2 host (conditional host) can also be 

used to describe hosts that have been experimentally infested (or infected) but 

for which field data or other evidence is lacking. The above terms may apply in 

one or more areas within the range of the pest, which should be specified. 

In some cases, pests may be associated with a host or other material, but not 

actually feeding on or infecting the host material. Examples of such 

associations include: 

snails that adhere to tiles.

pupae in packing boxes.

pests that attack parts of the host plant other than fruit, but that “hitchhike” 

with the fruit.

In these cases, the host material is not a food source, but may serve as a 

substrate for the pest to move in trade. The most applicable term for such 

materials (including fruit, boxes, or other material where the pest is present but 

is not feeding / infesting the fruit or vegetable) is “fomite” (Type 4 host).

Type 1 host (natural host). A plant species that becomes infested or infected by a plant 

pest in nature under natural conditions (e.g., natural, cultivated and/or unmanaged plants) 

and the plant pest is sustained on that plant species. No other trials are necessary to confirm 

host status.

Type 2 host (conditional host). A plant species that is only a host or a non-host under 

defined narrow range of conditions, respectively (e.g., host variety, stage of host maturity, 

other physiological conditions of the host, environmental, ecological or other physical conditions). 

Type 2 Hosts can be considered:

 Type 2a. A non-host becomes a host (example: lemons become a fruit fly host under 

heavy population pressure and drought; artificially inoculated laboratory hosts for some 

plant viruses, viroids, or phytoplasmas).

 Type 2b. A host becomes a non-host (example: avocados are generally a fruit fly host, 

but ‘Hass’ avocados are a non-host for some species of fruit flies).

Type 3 host (natural non-host). A plant species that does not become infested or infected 

by a plant pest under natural conditions (e.g., natural, cultivated and/or unmanaged plants) 

and the plant pest is not sustained on the plant species, nor can the pest survive, perpetuate 

itself or spread. 

Type 4 host (fomite). An object or material (including a harvested plant part) that may be 

contaminated with a pest and that could transmit that pest from one place to another.
Supplements and References

Supplement 3: Host Status

08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-16

Evidence and information sources

Background

There are many sources of information for host status, including original 

refereed scientific literature, various types of compendia, scientific reviews, 

interception records, NPPO records, and technical reports, as well as other 

sources that are less reliable (e.g., websites, news articles, etc.). Host records 

from reputable refereed scientific publications are considered to be the most 

reliable. Whenever possible, the original source of information should be 

checked and referenced for any host record, even for pests that are well 

understood. In some cases, this may involve going back in the literature a 

hundred years or more. In cases where the original reference(s) cannot be 

obtained, the analyst should trace back the information as far as possible. 

Various types of compendia are often available and very useful sources of 

information. However, care should be taken in interpreting information in such 

compendia, particularly with regard to host status (as well as geographic 

distribution). The problem arises because original evidence is sometimes 

misinterpreted when it gets added to different compendia, but once a reference 

is established, it becomes ingrained in the literature and is rarely questioned or 

validated. 

Interception records are also common sources of information for associating a 

pest with a host. In cases where there are repeated interceptions, these records 

can provide a useful basis for judging host status. However, single or a few 

interception records, especially those on baggage (vs. commercial fruit) should 

be interpreted with caution. In the absence of any other corroborating 

information, single interception records are generally not indicative of a hostpest association. 

Figure 3-2 provides a discussion of the types of evidence that is used for 

determining host status, and the corresponding (relative) level of reliability. In 

general, information from well-known, peer-reviewed scientific journals and 

identifications done by taxonomic specialists are viewed to be the highest in 

reliability and should be considered accordingly. For pathogens in particular, 

Koch’s postulates should also be considered in determining host status of the 

plant species. When a pathogen is associated with a diseased plant, proof of its 

role as the cause of the disease may be established by completing several steps 

known as Koch’s Postulates (after the 19th century bacteriologist, Robert 

Koch). 

Koch’s Postulates to prove pathogenicity are (definitions adapted from 

Shurtleff and Averre, 1997; Falkow, 2004)
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1. Consistent association. Consistent association of a suspected causal agent 

with a disease.

2. Isolation. Isolation of the pathogenic agent and its growth in pure culture. 

This may be difficult with some kinds of pathogens, e.g., obligate parasites, 

non-culturable organisms, but specialized methodologies, transmission 

studies, or consistent association with other isolated molecular markers can 

contribute to identifying and characterizing non-culturable pathogens. For 

example, some plant viruses can be isolated by means of transmission to 

experimental hosts or cells by insect vectors, parasitic plants or grafting, 

then used to re-infect healthy plants of the original host species. Reinoculation: Inoculation of healthy plants with prospective pathogen must 

produce the same symptoms as the initial disease described. Re-isolation: 

The pathogen must be re-isolated from the inoculated, diseased plant and 

identified as being identical to the original pathogen.

Recommendation 2: Interpretation and evaluation of evidence related to 

host status

Table 3-2. Reliability of evidence. Criteria for evaluating the reliability of evidence from most reliable (1) to 

least reliable (8). Table adapted from M. Hennessey, unpublished, and ISPM No. 8, Determination 

of pest status in an area (IPPC, 1998). A=arthropod; P=Pathogen.

Type of evidence

Host status determination method How 

recorded

Pest/

plant collector

Pest/

plant 

identifier

Location 

and date 

precision

Relative level of reliability of evidence

1 A Reproductively viable adult reared out of natural infestation on plant or from commercial or 

commercial grade consignment in trade (if origin traceable).

NPPO 

record 

(e.g.,, 

many 

interception 

records); 

refereed 

publication

Taxonomic 

specialist

Discriminating biochemical, 

serological, or 

molecular 

diagnosis

Delimiting 

or detection survey

P Koch’s postulates completed with cultures/isolates from natural infection on plant or from 

commercial or commercial grade consignment 

in trade (if origin traceable).

2 A Viable adults from forced field infestation of 

green or commercial harvestable grade plant.

Refereed 

scientific 

or technical journal

Professional 

specialist

Specimen 

maintained in 

an official 

collection; taxonomic 

description by 

specialist

Other field 

or production survey

P Koch’s postulates have not been completed, 

but the pathogen can be grown in pure culture 

and successful inoculations made with, for 

example, single spore isolates (or equivalent 

for organisms other than fungi), resulting in 

development of the same symptoms.
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3 A Viable adults from lab infestation (choice or 

non-choice) of green or commercial harvestable grade plant.

Official 

historical 

record; 

State 

Extension 

Service 

Bulletin; 

plant disease clinic 

report; a 

few interception 

records

Scientist Specimen 

in a general collection

Casual or 

incidental 

field 

observations, possible with 

no defined 

location or 

date.

P Pathogen cannot be grown in culture, but successful inoculations can be made, for example 

by insect vectors, graft transmission, or parasitic plants (dodder) from naturally infected 

plant material to healthy plants, resulting in 

development of the same symptoms. The 

pathogen is consistently associated with the 

disease in the host.

4 A Lab infestation of ground or non-commercial 

grade plant.

Non-refereed scientific or 

technical 

journal or 

publication

TechnicianDescription and 

photo

Observation with/

in products or byproducts; 

interception

P Successful laboratory inoculations are made, 

for example, by mechanical transmission, but 

only to experimental hosts, no evidence that 

the pathogen infects plants in nature, in cultivation, or production systems.

5 A Reproductively viable adult reared from 

ground, damaged, or non-commercial grade 

plant.

Specialist 

amateur 

publication

Expert 

amateur

Visual 

description only

Precise 

location/

date 

unknown P

Relative level of reliability of evidence

6 A Oviposition observed but no viable adults, 

pupae, larvae, or eggs in plant.

Unpublished scientific or 

technical 

document

Non-specialistNon specialist

P Plants produce symptoms characteristic of 

infection with specific pathogen, without any 

confirmation of the organism causing the disease.

7 A Plants produce general symptoms of a disease 

or infestation.

Non-technical publication; 

periodical 

or newspaper

P

8 A Host status determination unknown. Unpublished personal 

communication

Collector 

unknown

Method of 

identification 

unknown

Location 

and date 

unknown

P

Table 3-2. Reliability of evidence. Criteria for evaluating the reliability of evidence from most reliable (1) to 

least reliable (8). Table adapted from M. Hennessey, unpublished, and ISPM No. 8, Determination 

of pest status in an area (IPPC, 1998). A=arthropod; P=Pathogen.

Type of evidence

Host status determination method How 

recorded

Pest/

plant collector

Pest/

plant 

identifier

Location 

and date 

precision
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3-19 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Interpreting evidence to determine host status

Background

There are two levels in determining host status. The first level is collecting 

evidence on actual experiments or data to establish host status. The second 

level is in interpreting the published data or other evidence to make a judgment 

as to what the host status is. As mentioned previously, numerous terms can be 

found in the scientific literature to describe host status, but for the purposes of 

PRAs done for commodities, the terms Type 1, 2, 3 and 4 hosts (natural host, 

conditional host, natural non-host, and fomite, respectively) should be used. 

Table 2 provides a list of terms used to describe host status and identifies, using 

the above terminology, how other terms found in the literature may be 

interpreted. 

Guidance to researchers on determining host status is available, at least for 

fruit flies, in the two regional standards and in the draft IPPC standard 

identified previously. These documents outline the experimental designs that 

should be used in determining host status. They also provide guidance on how 

to interpret results of various types of tests (e.g., laboratory testing, field 

samples, cage testing). When host status testing follows such protocols, it is 

relatively simple for risk analysts and regulators to make a determination on 

host status. However, in many cases, the available literature is based on 

experiments that have not followed specific protocols but that nonetheless 

identify the host status of plants. Furthermore, because the available evidence 

can be highly variable in quality, experimental design, and numerous other 

factors, risk analysts must make certain judgments about host status based on 

the available evidence. 

The categories for natural host and natural non-host are often relatively clear 

and easy to interpret from the literature. In cases where a pest can complete its 

life cycle and/or a population can be naturally sustained on that plant, or in 

other words, the pest can survive, multiply, and spread via an infected or 

infested plant part, then the host may be regarded as a “natural host.” In 

contrast, if a pest cannot complete its life cycle, and/or a population cannot be 

naturally sustained on a plant, then that plant is considered a natural non-host. 

Not surprisingly however, “conditional hosts” are the most difficult to 

understand or interpret, particularly with regard to the level of risk they may 

pose. A conditional host may be either a natural host that can be a non-host 

under specific conditions, or it may be a natural non-host that can be a host 

under specific conditions. The conditions that affect whether a plant may be a 

host or not include:

host variety,
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physiological state of the host (including ripeness, life stage of pest on 

specific plant parts), 

barriers to transmission of the pest (host to vectors, and vice versa),

geographic variations in pests (including strains or races) or hosts, and

environmental conditions (including seasonality, drought, or other 

conditions).

The risk analyst must make a judgment about the host status based on the 

quality of evidence and the type of evidence provided (e.g., field studies, 

laboratory studies, etc. See Recommendation 2), especially for Type 2 hosts. 

For Type 2 hosts, there must be specific evidence describing the exact 

conditions under which a plant becomes a host or non-host. Table 3-3 provides 

recommendations for host status descriptions.

Recommendation 3: Procedure for identifying host status in PRAs

Use Table 3-3 to determine whether a plant is a Type 1, 2 or 3 host. The first 

row shows the harmonized terminology that should be used. Subsequent rows 

show terms that may be occur in the literature and suggest how those terms 

should typically be interpreted. In examining evidence, Recommendation 2 

should also be followed. Figure 3-3 provides a flow chart to aid in examining 

evidence and making a judgment as to host status. 
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Table 3-3. Recommended classification of definitions found in the literature for host status according to 

terminology for Type 1, 2, and 3 hosts; level of host associations and uncertainty expected for the 

type of host status. For both association and uncertainty, these levels are estimated and 

generalized, and are intended for description purposes only. There maybe be cases where either 

association or uncertainty differ from what is listed here.

Continuum of host status from natural host to natural non-host 

Type 1 host: 

natural host

Type 2 host: 

conditional host

2a: host

Type 2 host: 

conditional host

2b: non-host

Type 3 host: 

natural non-host

Term Level of 

association 

with the 

host

Expecte

d uncertainty

Term Level of 

association 

with the 

host

Expecte

d uncertainty

Term Level of 

association 

with the 

host

Expecte

d uncertainty

Term Level of 

association 

with the 

host

Expecte

d uncertainty

Host H, M C, MC Conditional 

host

H, M C, MC, 

MU

Conditional 

non-host

L, N C, MC Non-host N C, MC

Field 

host

H, M C, MC Experimental 

host

M, L MU, U Experimental 

host

M, L MU, U

Primary 

host

H, M C, MC Laboratory hostM, L MU, U Laboratory hostM, L MU, U

Preferred 

host

H, M C, MC Occasional 

host

M MC, MU Poor 

host

L MU, U

Commercial 

host

H, M C, MC Secondary hostH, M, L (MC), 

MU

Unusual 

host

L MU, U

Wild 

host

H, M C, MC Minor 

host

M, L C, MC, 

MU

Rare 

host

L MU, U

Non-preferred 

host

M, L MC, MU
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08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-22

In the case of fomites, there should be documented evidence that a pest is 

associated with the material in question. This evidence can come from the 

scientific literature, NPPO reports, or other technical documents. One of the 

most common sources of evidence for pest association with a fomite is port 

interception records. Examples of fomites or pest association with fomites 

include: 

EXAMPLE Commodity of plant origin: pest feeds on or infects plant, but not 

exported plant part; pest associated with plant but does not feed on 

or infect plant or exported plant part; pest intercepted with 

commodity, but no other documentation available (e.g., a true 

hitchhiker)

Commodity of non-plant origin: tiles/stone; vehicles/machinery

Material associated with the commodity: boxes containing plant 

parts; wrapping materials; packing materials or containers

Containers/conveyances: shipping containers; railway cars; ships 

and other vehicles

Other: soil; growing media; leaves, twigs, or other prohibited 

materials
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Relationship of host status to risk

The level of pest association and uncertainty for Type 4 hosts (fomites) is 

variable, and depends on the type of pest, the type of association of the pest 

with the fomite, the potential for moving in trade or other means, the potential 

for mitigation (e.g., cleaning, removal of pests, treatments), and other factors. 

Therefore, fomites can only be addressed on a case by case basis and general 

guidance on the level of risk posed by fomites is not possible. 

For Type 1 hosts (natural hosts), the expected level of association of the pest 

with the host (i.e., that the pest is associated with the plant part of a particular 

species) will in most cases be high or at least medium, and the level of 

uncertainty will be relatively low (i.e., certain, moderately certain). Likewise, 

for natural non-hosts, the level of association of a pest with the host will be 

negligible, with low uncertainty (i.e., certain, moderately certain). 

There may be greater uncertainty when determining whether a Type 2 host 

(conditional host) can be a host or non-host. However, the determination that a 

Type 2 host is a non-host (e.g., Type 2b or a non-host under specific 

conditions) should only be made when there is low uncertainty (i.e., certain or 

moderately certain). If uncertainty is judged to be moderate or more than 

moderate, then a conservative interpretation of the data should be made and the 

host status should be determined to be a Type 1 host. 

In all cases, the determination of host status can be accompanied by both a 

specified level of likelihood of association (using the recommended 

terminology) and uncertainty. The specified level of likelihood of association 

and the uncertainty are useful for making judgments in PRAs as to whether a 

pest may be expected to follow a particular pathway. 
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08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-24

Examples, exceptions, and uncertainty

Analysts should be aware that there are always exceptions or unusual 

circumstances that can affect host status. Perhaps one of the most well-known 

examples is that of lemons serving as a host of Medfly (the Mediterranean fruit 

fly). It was commonly understood that lemons were not a host of Medfly, until 

Medfly was intercepted in imported lemons. In reviewing the evidence, it was 

determined that during an exceptionally dry year, and a year with an 

exceptionally high Medfly population, the pests were able to overcome the 

natural resistance of lemon fruit to Medfly, and populations were able to 

successfully develop on lemons. This situation, therefore, proved to be an 

exception to the conventional wisdom concerning the host status of lemons. 

Following are some additional examples of pests and types of hosts.

EXAMPLE Plum pox virus

Natural host range (Type 1 hosts): Prunus armeniaca, P. 

cerasifera, P. domestica, P. glandulosa, P. persica, P. insititia, P. 

spinosa, P. salicina, P. cerasus, P. avium, Juglans regia 

Experimental hosts (Type 2 hosts): Capsella bursa-pastoris, 

Celosia argentea,Chenopodium capitatum, C. ambrosioides, C. 

foetidum, C. foliosum, C. murale, C. quinoa, Cyamopsis 

tetragonoloba, Emilia sagittata, Gomphrena globosa, Humulus 

lupulus, Hyoscyamus niger, Lupinus albus , Lycopersicon 

esculentum, Melilotus albus, M. officinalis, Nicandra physalodes, 

Nicotiana acuminata, N. benthamiana, N. bigelovii, N. clevelandii, N. 

debneyi, N. glutinosa, N. megalosiphon, N. occidentalis, N. rustica, 

N. sylvestris, N. tabacum, Petunia × hybrida, Physalis floridana, P. 

peruviana, Pisum sativum, Ranunculus arvensis, R. sardous, 

Senecio vulgaris, Sesbania exaltata, Sorbus domestica, Stellaria 

media, Trifolium pratense, T. repens, Vicia sativa, V. villosa, Zinnia 

elegans

EXAMPLE Anastrepha distincta (Peru citrus)

Literature (Norrbom and Kim, 1988) lists only laboratory and 

questionable reports of A. distincta on citrus. 

Based on this evidence, it was determined that this fruit fly species is 

not likely to be associated with commercial citrus for export (Type 3 

host). 
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Interception can be valuable in establishing potential pathways, but data should 

be scrutinized carefully and used cautiously.

EXAMPLE Monilinia fructigena in the United States

Guignardia citricarpa in Peru

EXAMPLE Sweet orange scab (Elsinoë australis)

Quarantine pest that has been intercepted on citrus from Peru by 

APHIS on multiple occasions. 

All interceptions were made from passenger baggage and ship’s 

stores or quarters. As such, the true origin of the fruit is difficult to 

determine. 

The disease has been reported from surrounding countries and 

flights from some of these countries to the United States connect 

through Peru.
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Figure 3-3. Determination of host status for PRA based on scientific evidence.
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Supplement 3: Host Status

3-27 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Appendix A: Recommendation for Prunus persica varieties to 

be considered non-hosts for Bactrocera cucurbitae

Current regulatory status. Peach (Prunus persica) is currently regulated 

domestically and internationally as a host of Bactrocera cucurbitae (melon 

fruit fly or MFF); however, nectarine (also P. persica) is not regulated as a host 

of MFF. Peach and nectarine are the same species; the only difference is that 

nectarines are a smoothed-skinned variety of Prunus persica lacking the 

typical velvety skin found on peaches. 

Taxonomy of MMF. This species has been described previously as 

Chaetodacus cucurbitae (Coquillet), Dacus cucurbitae Coquillet, Strumeta 

cucurbitae (Coquillet), and Zeugodacus cucurbitae (Coquillet). The current 

accepted name is Bactrocera cucurbitae (Coquillet).

Status of MMF in the continental United States. Although MFF has been 

long established in Hawaii, it is not established in the continental United 

States. It is periodically introduced and eradicated in California. It primarily 

occurs in parts of Asia and the Pacific region, and sporadically in Africa. 

Hosts of MFF. MFF primarily attacks plants in the family Cucurbitaceae 

(pumpkins, squash, gourds, cucumbers, melons and related species). It can 

attack fruits and flowers, as well as occasionally stems and roots. There are 

numerous unconfirmed records on non-cucurbit hosts and non-cucurbit hosts 

are considered to be uncommon.

Host status of Prunus persica varieties for MFF. There are very few reliable 

records of MFF infesting peach and no records of MFF infesting nectarines. 

White and Elson-Harris (1992) provide the following information “Other 

Hawaiian records are....peach (Prunus persica)...(Harris et al., 1986b; 

Maehler, 1951; Nakagawa et al. 1968)” (pg 265). 

When the original references are checked, neither Maehler (1951) nor 

Nakagawa et al. (1968) actually mention peach as a host of MFF. Harris et al. 

(1986) mentions that peaches were collected in Hawaii to look for adult 

emergence; however, no adult MFF emerged from peach in any of the 

collections over a two-year period of the study. In the original Harris article, 

peach is listed as a “rare host” even though no flies have ever been collected 

from peach. 

In White and Elson Harris (1992) in the “Useful plants and their associated 

tephritids” section, Prunus perscia is listed as an “unusual host” (pg. 473).

Back and Pemberton (1917) reared a single fly from peach in 1914. This is the 

only reliable record of MFF being associated with peach. 
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According to a review by Liquido et al. (unpublished), MFF has never been 

collected from peach in any records between 1949 and 1991 in Hawaii. There 

are no other reliable records or scientific publications that conclusively show 

peach (or nectarine) serves as a host for melon fruit fly. 

Recommendation. Based on the available scientific evidence, it is 

recommended that neither peach nor nectarine (e.g., any variety of Prunus 

persica) be regulated domestically or internationally for melon fruit fly 

(Bactrocera cucurbitae). 

References

Back, E.A. and C.E. Pemberton. 1917. The melon fly in Hawaii. USDA 

Bulletin No. 491. GPO. Washington. 

Harris, E.J., Takara, J.M., and Nishida, T. 1986. Distribution of melon fly 

Dacus cucurbitae (Diptera: Tephritidae), and host plants on Kauai, Hawaiian 

Islands. Environmental Entomology, 15, 488-493.

Liquido, N., P.G. Barr and G.T. McQuate. Unpublished. Host plants of melon 

fruit fly Bactrocera cucurbitae Coquillet (Diptera: Tephritidae)

Maehler, K.L. 1951. Notes and exhibitions (March 13, 1950). Proceedings of 

the Hawaiian Entomological Society, 14, 205-207.

Nakagawa, S., Farias, G.J. and Urgao, T. 1968. Newly recognized hosts of the 

Oriental fruit fly, melon fly and Mediterranean fruit fly. Journal of Economic 

Entomology, 61, 339-340. 

White, I.M. and M. M. Elson Harris, 1992. Fruit flies of economic 

significance: their identification and bionomics. CAB International. 

Wallingford. 
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Supplement 4: Evaluation of Evidence

Separating uncertainty arising from the lack of knowledge from ratings is 

important; ratings are made based only on the available evidence, not the 

uncertainty associated with the evidence. For instance, a given element should 

not be rated higher if there is a lot of uncertainty; rather the rating should be 

assigned based on available evidence, but the high level of uncertainty should 

be noted. 

The uncertainty associated with the available evidence should be evaluating in 

terms of both its reliability and its applicability (Table 3-4). 

Reliability refers to how reliable the source of the information is in terms of the 

quality of the source, age of the source, the methodology used, and the degree 

of consensus. The quantity of information available can also be used in 

evaluating resources. For example, many resources from lower quality sources 

that have the same conclusion may be more powerful in terms of certainty than 

a single reference from a higher quality publication source. 

Applicability refers to how applicable the information is to your situation. In 

most cases, the risk rating should be based on evidence on how the pest is 

currently behaving in the situations that correspond to the PRA area. Since this 

information is not always available, we must extrapolate and make 

assumptions, but emphasis should always be placed on how the pest behaves in 

the parts of the distribution most similar to the PRA area.

Table 3-4. Reliability of sources of information from low to high.

Publication source Reliability Examples

1 Well-known/respected 

peer-reviewed journal 

(English language or 

translated into English

Low None

ML Few or no original research papers; any found do not describe methodology OR methodology used is not widely accepted.

MH At least one original research paper with detailed description of methodological approach. 

Several original research papers without specified methodology.

Multiple published review articles; articles cite independent (separate) 

sources of information.

High Multiple original research papers with detailed description of the 

methodological approach(es) used; approaches are widely accepted. 
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2 Obscure or less-well 

known/respected peerreviewed journals (English language or translated into English)

Low No original research.

Few or no review or summary articles.

ML Few or no original research papers; methodology may or may not be 

described.

Multiple published review articles which may or may not cite independent (separate) sources of information.

MH Multiple original research papers (with specified methodology).

High Many original research papers (by multiple authors) that include a 

detailed description of the methodological approach(es) used; 

approaches are widely accepted; supported by other evidence.

3 Foreign language peerreviewed journals 

(abstract in English)

Low Few or no review or summary articles.

No supporting evidence found.

ML Multiple review articles research papers (which may or may not cite 

independent (separate) sources of information.

MH Multiple original research papers (methodology specified in abstract).

High n/a

4 Other reputable sources 

(e.g., universities, 

experts, scientific societies)

Low Few or no reports; those that are found may or may not be based on 

independent (different) information sources.

No supporting evidence found.

ML Several articles and reports that may or may not have each been 

based on independent (different) information sources.

MH Many articles and reports; each article/reports is based on independent information; methodology is described.

High n/a

5 Information from trading partnerLow Evidence not well-documented or inconsistent with other sources; 

methodology not verified or it is not widely accepted.

ML Evidence well-documented and consistent with other sources; methodology has either not been verified or it is not widely accepted.

MH Well-documented evidence that is generally consistent with other 

information; methodology verified and widely accepted.

High Well-documented evidence; methodology verified and widely 

accepted; supported several other sources.

Table 3-4. Reliability of sources of information from low to high.

Publication source Reliability Examples
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6 Scientific consensus Low May or may not have scientific consensus.

Methodology may or may not be generally accepted.

NPPO may or may not have experience with pest; if so, the evidence 

is may or may not be consistent with NPPO experience.

ML May or may not have scientific consensus.

Any methodology described may or may not be generally accepted.

NPPO may or may not have experience with pest; if so, the evidence 

is generally consistent with NPPO experience.

MH General consensus in scientific literature and other sources (but may 

include a few contradictory reports).

Methodological approaches used are generally accepted.

Evidence consistent with NPPO experience w/ pest.

High High consensus in scientific literature and other sources (no or practically no contradictory evidence found).

Methodological approaches are widely accepted.

Evidence generally consistent with NPPO experience w/ pest.

Table 3-4. Reliability of sources of information from low to high.

Publication source Reliability Examples

Table 3-5. Applicability of sources of information from low to high.

Publication 

information Applicability Examples

1 Species-specific data Low Species-specific data were limited; most of the species data were 

approximated or extrapolated from congeneric species, or other similar species.

ML Species-specific data were used; some of the species data were 

approximated or extrapolated from congeneric (or other) species 

known to behave similarly.

MH Species-specific data were used.

High Data for both species were used.

2 Environment-specific 

data

Low Environment-specific data were limited; no close proxy data was 

available; extrapolations were based on situations that may or may 

not be applicable.

ML Some environmental-specific data were used, but most were approximated or extrapolated from similar situations (i.e., research conducted in the areas of comparable climate, on a closely related host).

MH Some environment-specific data were used, but at least some data 

were approximated or extrapolated from similar situations (i.e., 

research conducted in the areas of comparable climate, on a closely 

related host).

High Environment-specific data were used.
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08/2012-1 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 3-32

Figure 3-4. Combining applicability and reliability of information to obtain a certainty rating.
Supplements and References

Literature Cited

3-33 Guidelines for Plant Pest Risk Assessment of Imported Fruit & Vegetable Commodities 08/2012-1

Literature Cited

7 U.S.C. § 7701-7786. 2000. Plant Protection Act, Title 7 United States Code § 

7701-7786.

Andrews, C. J., D. M. Hassenzahl, and B. B. Johnson. 2004. Accommodating 

Uncertainty in Comparative Risk. Risk Analysis: 24 (5) 1323-1335.

Bale, J.S., Masters, G.J., Hodkinson, I.D., Awmak, C., Bezemer, T.M., Brown, 

V., Butterfield, J., Buse, A., Coulson, J.C., Farrar, J., Good, J.E.G., Hartley, R., 

Jones, T.H., Lindroth, R.L., Press, M.C., Symrnioudis, I., Watt, A. and 

Whittaker, J.B. (2002) Herbivory in global climate change research: direct 

effects of rising temperature on insect herbivores. Glob Change Biol 8: 1–16.

Colyvan, M. 2008. Is Probability the Only Coherent Approach to Uncertainty? 

Risk Analysis: 28 (3): 645–52.

EFSA. 2006. Guidance of the scientific committee on a request from EFSA 

related to uncertainties in dietary exposure assessment.

EFSA. 2007. EFSA's 10th Scientific Colloquium. Pest risk assessment - 

Science in support of phytosanitary decision making in the European 

Community. Summary Report. December 6-7, 2007. Parma, Italy.

Falkow, S. 2004. Molecular Koch’s postulates applied to bacterial 

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