NAME OF THE ORGANISM: Ditylenchus destructor DITYDE

GENERAL INFORMATION ON THE PEST

Name as submitted in the project specification (if different):

Pest category:

Nematoda

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?

Yes

Is the pest defined at the species level or lower?:

Yes

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: Ornamental sector

If necessary, please list the species:

Is it justified that the pest is listed at a taxonomic rank below species level?

Not relevant

Conclusion:

Candidate: Ornamental sector

Justification (if necessary):

2 – Status in the EU:

Is this pest already a quarantine pest for the whole EU?

Presence in the EU:

Yes

List of countries (EPPO Global Database):

Austria (2014); Belgium (2007); Bulgaria (2001); Czech Republic (2001); Estonia (2008); France (2001); Germany (2014); Greece (2001); Hungary (1992); Ireland (1998); Latvia (1998); Luxembourg (2001); Netherlands (2015); Poland (2012); Romania (2011); Slovakia (1996); Sweden (1992); United Kingdom (2001); United Kingdom/England (2014); United Kingdom/Scotland (2014)

Conclusion:

candidate

Justification (if necessary):

The Standing Committee agreed in February 2015 to request EFSA for a complete Pest Risk Assessment before taking a decision about the future regulatory status of this pest in the EU (EU COM, 2015). This complete PRA was published in 2016 (EFSA-PLH 2016). Data of the presence of this pest on the EU territory are available in EPPO Global Database (https://gd.eppo.int/). The nematode is sporadically present in the majority of EU Member States (EFSA, 2014).

HOST PLANT N°1: Hyacinthus (1HYAG) for the Ornamental sector.

Origin of the listing:

IIA2AWG

Plants for planting:

Miniature cultivars and their hybrids intended for planting

3 - Is the pest already listed in a PM4 standard on the concerned host plant?

Yes

Conclusion:

Qualified

4 - Are the listed plants for planting the main* pathway for the "pest/host/intended use" combination? (*: significant compared to others):

Yes

Conclusion:

Candidate

Justification:

D. destructor attacks a wide range of ornamental and vegetable species, however EFSA quotes only two references, one from 1984 listing hyacinth as a host (only extract available) and one mentioning bulb nematode of iris, narcissus and hyacinth (indistinguishable morphologically from D. destructor), but no other details. However EPPO's classification scheme states Ditylenchus destructor causes whitish or light green spots or stripes on the leaves and flower parts. Infested bulbs, when cut open, show the tissues of some or all scales to be dry and granular, and light or dark brown in colour. Heavily infested bulbs can dry completely during storage, and a nil tolerance for all Ditylenchus spp is required (EPPO 2002).
The conclusion by EFSA was that Hyacinthus is probably a host plant (EFSA-PLH 2016).
In conclusion, young plants for transplanting or bulbs are both pathways, and with suitable control measures carried out for the alternative inoculum sources, plants and bulbs can be considered as significant pathways compared to others.

5 - Economic impact:

Are there documented reports of any economic impact on the host?

Justification:

The reproductive potential of D. destructor is high. It can be assumed that even a small population of D. destructor, present in the soil at the beginning of the growing season, could develop into a very large population causing severe damage to infested host plant. D. destructor can cause significant damage to the below-ground parts (roots, tubers, bulbs) of host crops such as potato and several ornamental plants. It reduces harvest yields of host crops and causes additional damage during storage. In recent years, potato tuber nematodes have caused serious problems on iris and garlic crops in Japan (EFSA, 2014).
However, D. destructor cannot survive dessication which may be one of the reasons why this species is much less of a problem than D. dipsaci.

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?

Conclusion:

Justification:

6 - Are there feasible and effective measures available to prevent the presence of the pest on the plants for planting at an incidence above a certain threshold (including zero) to avoid an unacceptable economic impact as regards the relevant host plants?

Conclusion:

Justification:

7- Is the quality of the data sufficient to recommend the pest to be listed as a RNQP?

Conclusion:

Justification:

CONCLUSION ON THE STATUS:

Not recommended for listing as an RNQP: the pest is qualified for RNQP status based on EPPO PM 4 Standard, however the requirement for absence of visual symptoms on the traded material (current general 'Substantially free from' requirement in the EU) is considered to be sufficient on this host.

8 - Tolerance level:

Is there a need to change the Tolerance level:

Yes

Proposed Tolerance levels:

Delisting.

9 - Risk management measures:

Is there a need to change the Risk management measure:

Yes

Proposed Risk management measure:

Delisting.

REFERENCES:

EFSA Panel on Plant Health (PLH) (2014) Scientific Opinion on the pest categorisation of Ditylenchus destructor Thorne. EFSA Journal 2014;12(9):3834. 31 pp. doi:10.2903/j.efsa.2014.3834
EU COM (2015) Recommendation of the Working Group on the Annexes of the Council Directive 2000/29/EC – Section II – Listing of Harmful Organisms as regards the future listing of Ditylenchus destructor Thorne;
EFSA Panel on Plant Health (PLH) (2016) Scientific opinion on the risk to plant health of Ditylenchus destructor for the EU territory. EFSA Journal 14(12):4602, 124 pp. doi:10.2903/j.efsa. 2016.4602;