Biology Reference
In-Depth Information
broadly two initiation points for invasive alien plants. PRAs may be appropriate for
the following:
●
Plants that have been (or are proposed to be) intentionally introduced for orna-
ment, and that have, or might in future, escaped from plantations to invade and
threaten unmanaged ecosystems (i.e. semi-natural or natural habitats). According
to Hodkinson and Thompson (1997), these species tend to be spreading peren-
nials with transient seed banks. Such species represent about 80% of invasive
alien plants (Hulme 2007). With respect to the PRAs performed so far by EPPO,
Crassula helmsii, Hydrocotyle ranunculoides, Lysichiton americanus, Pueraria
lobata, H. sosnowskyi, H. persicum
, and
Eichhornia crassipes
fall into this
category.
●
Plants that are unintentionally introduced as contaminants associated with inter-
national movement of various commodities and articles, including soil and
vehicles. According to Hodkinson and Thompson (1997), these plant species are
often small and fast growing, but their most unifying characteristic is the produc-
tion of numerous, small, persistent seeds. Grain and seeds for planting are
important commodities likely to act as a pathway for unintentional introduction
of such plants. Because such plants are originally associated with the agricul-
tural or managed plants or plant products that are traded, they are also likely to
be a greater threat to agriculture and cultivated ecosystems (as weeds) than to
uncultivated ecosystems. With respect to the PRAs performed so far by EPPO,
Solanum elaeagnifolium
and
Polygonum perfoliatum
fall into this category.
16.5.2
Pest Risk Assessment
16.5.2.1 Pest Categorization
A rapid qualitative assessment is first made, with little information, to determine
whether the organism meets the criteria of the definition of a quarantine pest (see
paragraph
Cooperation between the IPPC and the CBD
) and could therefore be
regulated in international trade. The main aim of this step is to avoid conducting a
full PRA in a case that can immediately be seen not to require one.
If the pest categorization step leads to a positive answer, the main PRA starts. It is
essentially composed of a series of questions, made in terms of “likeliness” for qualita-
tive questions (very unlikely, unlikely, moderately likely, likely, very likely), and an esti-
mate for quantitative questions (very few, few, moderate number, many, very many).
16.5.2.2
Probability of Introduction
Introduction, as defined by the
Glossary of phytosanitary terms
is the entry of a pest
resulting in its establishment. Entry and establishment are separate processes and
