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):

Listing of hosts at the genus level is coherent because D. destructor is highly polyphagous.

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: Tulipa (1TULG) 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

Justification (if necessary):

The EPPO classification scheme PM 4/13(2) requires a nil tolerance at GSI for Grade A material intended for further propagation and for Grade B intended for flowering, and a 1% tolerance is permitted at dry bulb inspection for Grade B, only (EPPO, 2002).

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, and EFSA concludes tulip is a good host plant with relatively large numbers of reports until 1984, with numbers decreasing since then (EFSA-PLH 2016). It was detected in lots of Tulipa for export and in 0 out of 16,060 field inspections in 2015 (Personal communication by P. Knippels, in EFSA-PLH 2016). Host plants infected by D. destructor are crucial for establishment of new field infestations, however the soil infection route is also important, and weed hosts seem to be important for maintaining nematode soil infestations both inside and outside crop fields. In addition, as D. destructor is very polyphagous, infested bulbs, rhizomes and roots of other host plants are important sources for establishment of new infestations. D. destructor is mycophagous and can survive in soil in the absence of host plants by feeding on many soil borne fungi (EFSA, 2014).
All these different sources of infestation are possible, however due to the known good host status of D. destructor in Tulipa overall, plants for planting are considered to be a significant pathway compared to other pathways for this pest/host/intended use combination.

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;
EPPO (2002) PM 4/13(2) Classification scheme for Tulip. Bulletin OEPP/EPPO Bulletin 32, 115–121;
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;