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: Crocus (1CVOG) for the Ornamental sector.

Origin of the listing:

IIA2AWG

Plants for planting:

Flower bulbs and corms 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 4/14 requires a nil tolerance at GSI for Grade A material intended for further propagation and for Grade B intended for flowering, but 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:

Crocus L. is reported to be a wild host of D. destructor according to the Pest Categorisation (EFSA PLH, 2014). Crocus is noted as a host plant until 1980, mostly as Dutch reports in yearbooks and was detected in consignment lots of Crocus for export and in 2 out of 617 field and 11 out of 617 post-harvest inspections in 2015 (Personal communication by P. Knippels, in EFSA-PLH 2016). No other records in crocus are reported by EFSA.
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).
In conclusion, bulbs can be a pathway, and with suitable control measures carried out for the alternative inoculum sources, bulbs could be considered as significant pathway compared to others.

5 - Economic impact:

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

Justification:

Overall 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 (EFSA, 2014). Very few reports indicate D. destructor infestation on flower bulb production and very limited number of bulb flowers contaminated with this nematode have been intercepted (EUROPHYT, online). EPPO's classification scheme says symptoms on bulbs appear on one side of the root crown as swollen discoloured tissue (dirty white to pinkish). This later becomes darker in colour and spreads into the bulb. When the bulb is cut transversely, a star-shaped brown area can be seen. Infested plants begin flowering earlier, leaves are shorter and have withered tips. The plants die back earlier than healthy ones (EPPO, 2002). No references to an economic impact of this pest on Crocus specifically are available.

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 4/14(2) Classification scheme for crocus. Bulletin OEPP/EPPO Bulletin 32, 123-128;
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;