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EWG on PRA for plants as quarantine pests (May 2009)
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Outline of Annex text
PEST RISK ANALYSIS FOR PLANTS AS QUARANTINE PESTS.
NEW ANNEX 4 to ISPM 11.
Outline, version 2009 January 8
From Ebbe Nordbo (steward)
Introduction.
The movement of plants in international trade is increasing as opportunities for international trade
increases. Whilst the high risk generally associated with plants, and in particular plants for planting
as a pathway for pests has been recognised since long, the consideration in the IPPC framework of
plant species themselves as potential quarantine pests is more recent.
Plants as pests
Plant species may be injurious to other plant species in various ways and therefore be pests of these
plants.
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Plant species growing at the same location compete for limited resources: space, light,
nutrients and water. The competition exerted by a certain plant species at a certain place and
time may be so strong that that species is categorized as a pest of other plant species.
Some plant species are parasites to other plant species.
Other plant species may injure other plant populations through hybridization, particularly
where non-indigenous plants establishes among indigenous plants.
Thus the protection of plants (as pursued through e.g. the IPPC) may include considering certain
plant species as pests, and controlling them or preventing their introduction and spread. Which
species are deemed as pests is a matter of human decision and varies with location and time. Pest
risk analysis may form the basis of such decision and subsequent decisions regarding possible
regulation of the plant species.
The terms ‘weed’ and ‘invasive alien plant’
Terms often used for plants that are pests of other plants (”plants as pests” hencefoprward) include
‘weed’ and the more recent term ‘invasive alien plant’.
‘Weed’ is often defined broadly as ‘a plant that is growing where it is not wanted by humans’ (cf.
‘Procedures for weed risk assessment’, FAO 2005). This definition does not specify the reason that
the plant is unwanted and may therefore include also plants that are not pests but unwanted for other
reasons, e.g. for breaking up buildings, dams etc. In a more narrow sense, however, a weed is a pest.
Often, the term is used solely for pests to cultivated plants. However, the term “weed” is sometimes
used for all plants as pests, irrespective of whether crops or wild flora are at threat1.
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Some countries use the term ’landscape weed’ or similar to distinguish from ‘weed’ affecting crops only.
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EWG on PRA for plants as quarantine pests (May 2009)
Document: 07
Discussion paper prepared by steward:
Outline of Annex text
‘Invasive alien plants’, on the other hand, in analogy to CBD terminology are plant species,
introduced by human agency and threatening biodiversity2. Biodiversity is normally understood as
encompassing the domestic flora rather than introduced crops3.
The distinction between cultivated plants and wild flora is not clear cut. Therefore, neither is the
distinction between ‘weed’ and ‘invasive alien plant’ clear cut. In any case, this distinction is not
relevant in the context of the IPPC, which is concerned with pests injurious to plants whether
cultivated or wild ( Annex 1). Thus, the present Annex covers plants as pests of cultivated as well as
wild plants4.
Scope
This Annex provides guidance for the conduct of PRA to determine if a plant identified as a pest of
cultivated or wild plants should be regulated as a quarantine pest.
Entry of plants into an area may be intentional for intended uses such as planting, consumption or
processing, or unintentional through contamination of, for example, soil, vehicles, containers,
ballast water, or consignments of seeds or grain. This Annex covers only intentional entries.
Particular analytical aspects regarding plants as pests
In the following, guidance is provided to analytical aspects regarding plants as pests. Reference is
made to relevant sections of the present ISPM as well as of ISPM No. 2 (2007).
To stage 1: The initiation stage.
PRA initiation point
For this Annex the initiation point triggering a conduction of a PRA would normally be that
 an import is proposed of a plant species (as growing plant, seed, grain, fodder etc.) not
previously imported or from a new area of origin
 a plant species is identified as a pest (cf. section 1.1.2 of ISPM No.2)
 phytosanitary policies relating to plants as pests are being reviewed (cf. section 1.1.3 of
ISPM No. 2)
Screening
Section 1.2 of ISPM No. 2 (2007) describes the early step of determining whether an organism is a
pest (sometimes termed pre-selection or screening). For plants as pests, ISPM No. 2 provides the
following guidance on screening:
The primary indicator that a plant species may become a pest in the PRA area is the existence of
reports that the plant species has been recorded as a pest elsewhere. Some intrinsic attributes that
may indicate that a plant species could be a pest include:
adaptability to a wide range of ecological conditions
2
In the footnote 57 to the Guiding Principles for the implementation of the Article 8(h) of the Convention of Biological
Diversity, ‘invasive alien species’ is defined as ‘an alien species which introduction and/or spread threatens biological
diversity’.
3
Cf. Appendix to ISPM No. 5: Terminology of the Convention of Biological Diversity in relation to the glossary of
phytiosanitary terns
4
Distinguishing between ‘weed’ and ‘invasive alien plant’ may be relevant for Contracting Parties nationally, as
differing legislation or authorities may be involved in regulating one or the other.
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EWG on PRA for plants as quarantine pests (May 2009)
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Document: 07
Discussion paper prepared by steward:
Outline of Annex text
strong competitiveness in plant stands
high rate of propagation
ability to build up a persistent soil-seed bank
high mobility of propagules
allelopathy
parasitic capacity
capacity to hybridize.
However, it should be noted that plants without such attributes may nevertheless become pests and
that long time lags have often been observed between the introduction of a new plant species and
evidence that the plant is a pest.
As for any type of organism, if the screening determines that the plant is not a pest, the PRA may
stop at this point. Otherwise, the PRA may continue with the risk assessment (stage 2).
To stage 2 Risk assessment:
In the following, particular guidance for plants as pests is provided regarding
 entry
 establishment
 spread
 economic impact.
Subsection Assessment of entry:
Given that the introduction is intentional, the probability of entry need not be assessed. However, it
is important to note the intended use of the plants to be imported as this may affect the subsequent
probabilities of establishment and spread. In that respect, the main distinction is between plants for
planting (including seeds) and plants for other purposes (consumption, processing etc.).
Uses of plants for planting include:
 planting as a crop (e.g. plants for horticulture, forestry or agriculture)
 planting for amenity (e.g trees and shrubs for gardens, parks and roadsides, aquatic plants
for ponds or aquarium)
 planting to combat soil erosion (e.g. plants for the protection of soil terrasses, dunes etc.)
Plants imported for planting thus are destined for a particular planting site (e.g. field, garden, pond,
etc.) which for the PRA purpose may be termed as the ‘intended habitat’. Any other site to where
the plant species may unintentionally spread and establish may be referred to as an ‘unintended
habitat’.
Other intended uses include:
 Human or animal consumption (e.g. fruits, grain)
 Combustion for energy production (e.g. grain, cuttings)
 Processing (e.g. fruits, grain)
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EWG on PRA for plants as quarantine pests (May 2009)
Document: 07
Discussion paper prepared by steward:
Outline of Annex text
In addition to the intended use, the PRA should take into account also envisaged volume, frequency,
distribution and routes of import as these parameters may influence the risk of establishment and
spread.
Subsection Assessment of establishment (cf. section 2.2.2).
For plants for planting, establishment in the intended habitat can be taken for granted. What needs
analysis in this step is the probability of establishment in an unintended habitat. Thus the analysis
should determine whether habitats other than the intended habitat exist where the plant could
establish. The suitability and extent of those other habitats should be determined.
For plants imported for other purposes there is no ‘intended habitat’. The analysis should determine
whether habitats exist where the plant could establish and the suitability and extent of such habitats.
The analysis of suitable habitats substitutes the analysis of host plants (except in the rare case of
parasite plants). However, these analyses are analoguous, such that the guidance provided in section
2.2.2 can be used with the understanding that the terms ‘host’ or ‘host range’ are read as ‘suitable
habitat’. As for other pests, the analysis should include considerations of
 Suitability of the soil, climate and biotic conditions in the habitat (cf. section)2.2.2.2.
 Cultural practices in the habitat (cf. section 2.2.2.3)
 Intrinsic characteristics of the plant as pest [cf. section 2.2.2.4])]
[For the EWG: Those 3 bullets need to be developed further.
e.g. bullet 1: Suitability of the soil, climate and biotic conditions in the habitat:Elaborate on
analysis of the suitability of
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Climate: use of climate models regarding current and projected climate ‘match’
Soil: topography, soil structure, texture, nutrient status and capacity, salinity, pH, water
capacity, etc.
Biotic conditions in the habitat: e.g. current vegetations competitive ability, grazing
preferences and capacity of animals, potential pests to the introduced plant etc.
e.g. bullet 2, cultural practices in the habitat:
Elaborate on analysis of effects of cultural practices in crops/managed plant communities (i.e.
effects of herbicides, cutting, soil cultivation, fire etc. is highly relevant), including side-effects
such as aerial deposition of nitrogen or pesticides etc.
e.g. bullet 3, intrinsic attributes of the plant species:
Elaborate on intrinsic attributes that may influence the probability of establishment, such as
 polymorphy of species
 hybridization potential
 self-compatibility
 vegetative reproduction
 reproduction frequency (growth to reproductive maturity, period between production of
offspring
 volume and viability (e.g. dormancy of seeds, tubers etc) of off-spring
 tolerance to herbicides, drought, salinity…
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EWG on PRA for plants as quarantine pests (May 2009)
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Document: 07
Discussion paper prepared by steward:
Outline of Annex text
dispersal mechanism
palability
Subsection Assessment of spread (cf. section 2.2.3).
The risk of natural spread from an area where the plant has established depends on:
 the intrinsic characteristics of the plant species (in particular propagative mechanisms)
 the existence of vectors (wind, birds…)
 the spatial pattern of suitable habitats and corridors in-between habitats
For the EWG: [These bullets (and more…?) to be developed further]
The risk of spread by human agency depends mainly on
 the actual use of the plants
 the economic value of the plants
 the ease of transport of the plants
 public awareness and effectivity of regulation.
For the EWG: [These bullets (and more…?) to be developed further]
Potential for spread (and serious economic impacts) may increase over time. Historically, long time
lags between an initial introduction and later spread has been observed in many cases. Possible
reasons for an increase of the spreading potential includes changes in
 Climate (such as warmer climate or changes in precipitation patterns)
 Other abiotic conditions (e.g. an increase in aerial deposition of nitrogen or sulphur)
 The genetic profile of the plant species (through natural selection, genetic drift etc.)
In addition, typically many plants with the potential of becoming pests are opportunists, e.g. relying
on an advantageous occurrence of voids in the vegetation to establish. Plants with a robust
dormancy combined with a prolific reproductive ability are well suited for such opportunistic
strategy.
Regarding stage 2 assessment, subsection Assessment of potential economic impact (cf. section
2.3)
Plants as pests may affect other plants in habitat types that traditionally have not been under the
jurisdiction of the NPPO, such as aquatic habitats (e.g. ponds, lakes, rivers).
For the EWG: The above statement is simply meant as a reminder that many NPPOs will be
‘reading new ground’.
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EWG on PRA for plants as quarantine pests (May 2009)
Document: 07
Discussion paper prepared by steward:
Outline of Annex text
As for any type of organism, if the risk assessment determine the plant species represents an
unacceptable risk, the PRA may continue with pest risk management (stage 3).
Regarding stage 3 Analysis of pest risk management option (cf. section 3.4)
For the EWG: [Section to be developed further. probably without any subsectioning as used in 3.4.
Regarding Information gathering (cf. ISPM 2, sect. 3.2)
For the EWG: [Section to be developed further, mentioning existing databases, and advocating for
bi- or multilateral systems of ‘early warning’]
Regarding Risk communication (cf. ISPM 2, sect. 3.4)
For the EWG: [Section to be developed further.
Risk communication seems particularly important at all stages of the PRA with plants as pests,
because (in contrast to the situation for most other pests) a desire exists to import the plant for an
intended use and thus a conflict of interest.]
Existing regional or national PRA tools for plants as pests
For the EWG: Consider whether such a section is useful & appropriate ! It has not been used in
other ISPMs, notably not in the ISPMs on PRA. However, the possibility sees to be opened with
Specification task 2.
A brief introduction could mention:
[In some countries or regions, tools exist for analysing ‘weeds’. ‘invasive plants’ or both.
These tools are often structured as sequential questions. The categories and also the sequences used
sometimes differ from what is presented in this ISPM/Annex.
In the various tools, replies to questionnaires are often pre-standardised into binary replies (yes/no)
or grades (e.g. low-medium-high) or quantitative scales (e.g. scores).
The EWG could consider providing an ultra-brief description (in an Appendix to the Annex !)
and/or links to tools developed and used by e.g..
EPPO
Australia
USA
Canada
South Africa
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EWG on PRA for plants as quarantine pests (May 2009)
Document: 07
Discussion paper prepared by steward:
Outline of Annex text
New Zealand
others….]
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