NAME OF THE ORGANISM: Onion yellow dwarf virus (OYDV00)
GENERAL INFORMATION ON THE PEST
Name as submitted in the project specification (if different to the preferred name):
Viruses and viroids
1- Identity of the pest/Level of taxonomic listing:
Is the organism clearly a single taxonomic entity and can it be adequately distinguished from other entities of the same rank?
Is the pest defined at the species level or lower?:
Can listing of the pest at a taxonomic level higher than species be supported by scientific reasons or can species be identified within the taxonomic rank which are the (main) pests of concern?
- Not relevant: Vegetable propagating and planting material (other than seeds) sector
Is it justified that the pest is listed at a taxonomic rank below species level?
- Candidate: Vegetable propagating and planting material (other than seeds) sector
2 – Status in the EU:
Is this pest already a quarantine pest for the whole EU?
Presence in the EU:
List of countries (EPPO Global Database):
Austria (1993); Czech Republic (2011); Denmark (1984); Estonia (1984); Finland (2011); France (1984); Germany (1993); Hungary (1992); Poland (1984); Romania (1984); United Kingdom (1993); United Kingdom/England (1994); United Kingdom/Scotland (1994)
Justification (if necessary):
Data of the presence of this pest on the EU territory are available in EPPO Global Database (https://gd.eppo.int/).
HOST PLANT N°1: Allium cepa (ALLCE) for the Vegetable propagating and planting material (other than seeds) sector.
Origin of the listing:
2 - Vegetable seedling sector: Commission Directive 93/61/EC
Plants for planting:
Plants intended for planting
3 - Is the pest already listed in a PM4 standard on the concerned host plant?
4 - Are the listed plants for planting the main* pathway for the "pest/host/intended use" combination? (*: significant compared to others):
The virus survives in bulbs, onion sets and volunteer onions and is transmissible during vegetative production by Myzus persicae. It is not transmissible through seeds or pollen, so provided seedlings for transplanting are produced from seed under protected conditions to prevent virus infection by aphids, planting material should not be infected. Therefore although seedlings can be considered a pathway it is not considered they would be a significant source compared to other pathways. For onion sets, however, these could be potentially infected during their production if grown outside and if all other inoculum sources were removed before planting by efficient cultivations etc, then sets could be considered a significant pathway compared to other sources.
5 - Economic impact:
Are there documented reports of any economic impact on the host?
Onion OYDV in onion can reduce yield and seed and bulb quality and causes symptoms early in the growth of the crop. Later leaves become crinkled and flattened and tend to fall over. Bulbs become undersized though remain firm. Scapes show intensive yellowing, twisting and curling and seeds are of poorer quality. Losses vary with the time of infection and infected seedlings may form very small or no bulbs whereas those infected later may produce reasonable bulbs (Compendium of Onion and Garlic Diseases, 2008). This virus is often found in association with other viruses of Allium. However no impact is observed on A. cepa (Messiaen et al., 1993).
What is the likely economic impact of the pest irrespective of its infestation source in the absence of phytosanitary measures? (= official measures)
Is the economic impact due to the presence of the pest on the named host plant for planting, acceptable to the propagation and end user sectors concerned?
Is there unacceptable economic impact caused to other hosts (or the same host with a different intended use) produced at the same place of production due to the transfer of the pest from the named host plant for planting?
Experts commented that symptoms are observed regularly in the NL. In absence of evidence of unacceptable economic impact, the RNQP status is questionable and the substantially free from requirement is considered to be sufficient.
CONCLUSION ON THE STATUS:
Disqualified: Not sufficient evidence of unacceptable economic impact. The 'Substantially free from' requirement would be sufficient.
8 - Tolerance level:
Is there a need to change the Tolerance level:
Proposed Tolerance levels:
9 - Risk management measures:
Is there a need to change the Risk management measure:
Proposed Risk management measure:
- Compendium of Onion and Garlic Diseases (2008) Second edition. The American Phytopathological Society;
- Messiaen JM, Leroux JP, Pichon M & Beyries A (1993) "les allium alimentaires reproduits par voie végétative" du labo au terrain. Edition INRA;