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Download: ISTA Reference Pest List

Can seed be a pathway for pests?
 - An update of the ISTA annotated list of seed-borne diseases  

Why is the list being revisited?

A recent issue of the International Standard for Phytosanitary Measures, provided by the International Plant Protection Convention (IPPC) and published by the Food and Agriculture Organisation (FAO) of the United Nations, was dedicated to the international movement of seeds (ISPM38, April 2017). This standard included the definition of seed-associated pests. A seed-borne pest is one carried by seeds externally or internally that may or may not be transmitted to plants growing from the seeds, causing their infestation. A seed-transmitted pest is a seed-borne pest that is transmitted via seeds directly to plants growing from these seeds, causing their infestation.  

In the context of seed trade, seed can be a pathway for the introduction and dissemination of pests in a new geographic area. Safeguarding seed health is critical in avoiding the trade-related spread of pests. Thus, it is of crucial importance to provide national plant protection organisations (NPPOs) with an updated, scientifically evidenced list of seed-associated pests. Phytosanitary requirements for the import of seed lots, as defined by NPPOs, have mostly been supported by the book An Annotated List of Seed-borne Diseases (1st Edition, 1958). However, the 4th and last edition of this book was published by ISTA in 1990 and is now outdated. Curating this reference is therefore necessary.  

How have the revisited crops been selected?

This challenge was initiated a few years ago under the framework of the European project TESTA–Seed Health. One objective was to identify references on seed-associated pests in hundreds of crops to update the current knowledge and to disseminate these through an updated annotated list, to be made available on the ISTA website. To avoid repetition, references related to vegetable species were transferred to the International Seed Federation (ISF), which is updating its own regulated pest list database. At ISTA, the Seed Health Committee (SHC) is focusing on non-vegetable species.  

The first part of the project (2018) has focused on cereals (barley, oat, rice, sorghum, triticale, wheat), legumes (alfalfa, soybean) and oleaginous crops (cotton, oilseed brassicas, sunflower). In 2019, the second part of the project will be dedicated to seed diseases in many other plant species, including forest trees (almond, cedar, chestnut, eucalyptus, firs, oak, peanut, Pinus spp., poplar, spruce, sycamore, walnut,…), fruit trees (apple, lemon, orange, papaya, pomegranate, Prunus spp., …), and legumes (chickpea, lentil, lupine). The webpage will be updated regularly as novel data becomes available regarding seed pests.  

How was the review process set up?

To successfully offer a robust, revised list of pests, the scientific relevance of hundreds of articles, and more particularly their conclusions on the seed-borne/-transmitted status of pests, was evaluated by a board of international experts in seed diseases in the investigated crops, working either in private seed companies
or in academic research laboratories. Each article has been reviewed by two to four referees who provided constructive reports to the project coordinator. These reviews have served to build the updated list, which was validated by the SHC members prior to public release.  

How to read the updated annotated list

Plants: The crop name and its binomial nomenclature (species); the names of the diseases.
Pests: Their current nomenclature, all the synonyms according to the databases Species 2000 & ITIS Catalogue of Life  and the Index Fungorum; their taxonomy (kingdom, phylum).  

*Pest interaction:
Is the crop a host for the pest? The answer is ‘Yes’, if the pest is pathogenic on the crop, causing disease. Otherwise, the answer is ‘No’. When the current knowledge is unclear or without strong support to a decision, the answer is ‘Not proven’.
Is the pest a pathogen or saprophyte? The answer is ‘Saprophyte’, if the pest only infests seeds during non-adapted storage conditions, or if it is associated with seeds without causing diseases on seedlings. Otherwise, the answer is ‘Pathogen’. When the current knowledge is unclear or without strong support to a decision, the answer is ‘Not proven’.  

*Seeds as a pathway for pest dissemination:
Is the pest seed-borne or seed-transmitted? The answers to these questions are based on scientific articles and due to the expertise of the worldwide panel of reviewers. When the conclusions are supported by our current scientific and practical (field experience) knowledge, the response is ‘Yes’ (it is proven that the pest is seed-borne or -transmitted) or ‘Not’ (it is proven that the pest is not seed-borne or -transmitted). When the current knowledge is unclear or without strong support to a decision, the answer is ‘Not proven’.
Is seed a pathway for pests? The answer to this question is ‘Yes’ for all the seed-transmitted pests and for seed-borne pests that can be introduced and disseminated; ‘No’ for non-disseminated pests and saprophytes; ‘Not proven’ when scientific evidence is still lacking or currently unclear.  

*Scientific articles:
Experimental design and results: A summary of the experiments performed in the laboratory and in the field to characterise the role of seeds in pest-crop interactions.
Remarks: Notes about the reference analysed.
References: Article source that was used to support the conclusions.  

*Completeness of the list:
The list is expected to evolve regularly, due to novel scientific evidence of the seed-borne/-transmitted status for a known pest, or after identification of a novel pest for a given crop. A continuous literature survey guarantees to be well-timed with novel discoveries and to provide accurate information on the webpage. However, it takes time to rigorously evaluate the scientific literature and some pests still under consideration are explicitly mentioned. Readers are encouraged to subscribe to the updates to stay tuned accordingly.  

Who are the contributors?

Funding: ISTA (Pest List project)

Coordinators: Valérie GRIMAULT (Chair of the ISTA SHC; Head of the Phytopathology Laboratory, Seed Testing Station, GEVES, France) and Nicolas DENANCÉ (Seed Testing Station, GEVES, France)  

Selection of evaluated articles: The articles were selected either during the TESTA project by Christine HENRY and Alex JEBB (FERA, UK), Terry AVELING, Nicole JOUBERT, Mahlane Godfrey KGATLERenaan THOMPSON, Edgar MANGWENDE and Gloria MUKWIRIMBA (University of Pretoria, South Africa), or during the ISTA Pest List project by Nicolas DENANCÉ (GEVES, France).

Validation of the lists: Members of the ISTA SHC.

Contact: If you have comments on the conclusions or new information to offer, please contact ISTA.


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