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, Seed potato sector, Vegetable seed 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, Vegetable seed sector
Not evaluated: Seed potato 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: Allium sativum (ALLSA) for the Vegetable seed sector.

Origin of the listing:

RNQP Questionnaire

Plants for planting:

Seeds

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

Conclusion:

Evaluation continues

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

Conclusion:

Not candidate

Justification:

D. destructor attacks a wide range of species, including garlic which is a good host (CABI, 2016) to 'may be only slightly infested' (EFSA, 2014), and is an endoparasite of the roots and underground modified plant parts, rarely on aerial plant parts, which show few symptoms. The main means of dispersal is with infested potato tubers or other subterranean organs of host plants, for example bulbs and rhizomes which can harbour adults, eggs and juveniles. Transport in infested soil is another important means of spread and irrigation water can also carry the nematodes.
The pest overwinters in soil as adults or larvae and may multiply by feeding on alternative weed hosts and on fungal mycelia. It may possibly overwinter as eggs which hatch in the spring and larvae are immediately able to parasitize hosts. In garlic bulbs, nematodes can be controlled by drying at 34-36°C for 12-17 days or using seed dressings with thiram or benomyl at sowing, and infestation in fields can be effectively controlled by flooding. Control by crop rotation is difficult due to its wide host range (CABI, 2016; EFSA, 2014).
No references to garlic true seed being infested with D. destructor could be found and therefore seed is considered not to be a pathway for this pest/host combination.

5 - Economic impact:

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

Yes

Justification:

No references to impacts in garlic in the EU (EFSA, 2014). In 1984, D. destructor was found in diseased garlic plants collected from a field in Japan and from 1984 to 1986, the total area of the infested garlic fields had extended over about 4 ha. When the nematode-infected bulbs were planted, many garlic plants died in the early stages of growth, and the basal plates of garlic bulbs in most of the plants which survived became dark and rotten at harvest time (Fujimura et al., 1986). D. destructor was also found infesting garlic in Canada (Yu et al., 2012).

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:

Disqualified: true seeds of garlic are not considered as a significant pathway.

8 - Tolerance level:

Is there a need to change the Tolerance level:

Proposed Tolerance levels:

Not recommended for the RNQP status.

9 - Risk management measures:

Is there a need to change the Risk management measure:

Proposed Risk management measure:

Not recommended for the RNQP status.

REFERENCES:

CABI (Centre for Agricultural Bioscience International) (2016). Datasheets Ditylenchus destructor (potato tuber nematode). Invasive species compendium. CABI, Wallingford, UK. Available from http://www.cabi.org/isc/datasheet/19286;
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;
Fujimura T, Washio S & Nishizawa T (1986) Garlic as a new host of the potato-root nematode, Ditylenchus destructor Thorne. Japanese Journal of Nematology 16, 38-47;
Yu Q, Zaida MA, Hughes B & Celetti M (2012) Discovery of potato rot nematode, Ditylenchus destructor, infesting garlic in Ontario, Canada. Plant Disease 96, 297;

HOST PLANT N°2: Begonia x hiemalis (BEGEH) for the Ornamental sector.

Origin of the listing:

Commission Directive 93/49/EEC

Plants for planting:

Plants intended for planting

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

Conclusion:

Evaluation continues

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

Conclusion:

Not candidate

Justification:

D. destructor attacks a wide range of ornamental and vegetable species, however EFSA states "begonias are probably wrongly reported as host plants as Goodey (1952) could not find nematodes associated with tubers. There are also no other reports substantiating the host status of begonias" (EFSA-PLH 2016). Therefore it is proposed to conclude begonia is not a host and the analysis is concluded at this point.

5 - Economic impact:

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

Justification:

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?

Conclusion:

Justification:

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:

Disqualified: Not enough evidence of the host status. Plants for planting are therefore not considered as a significant pathway for this host.

8 - Tolerance level:

Is there a need to change the Tolerance level:

Proposed Tolerance levels:

Delisting.

9 - Risk management measures:

Is there a need to change the Risk management measure:

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 12, 3834;
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, 4602;
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;

HOST PLANT N°3: 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?

Conclusion:

Justification:

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;

HOST PLANT N°4: Gladiolus (1GLAG) 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?

Conclusion:

Evaluation continues

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 suggesting the nematodes from Gladiolus were probably feeding on fungi rather than the roots, and the other that there was inconclusive evidence as a host and D. destructor was able to multiply after bulb storage, but maybe on Botrytis. The conclusion was of unclear status but Gladiolus is most likely not a host plant (EFSA-PLH 2016). However experts reported information from the NL inspection services saying that Gladiolus, especially Gladiolus nanus and Gladiolus x colvillei, is a host plant.

5 - Economic impact:

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

Yes

Justification:

What is the likely economic impact of the pest irrespective of its infestation source in the absence of phytosanitary measures? (= official measures)

Minor

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?

Conclusion:

Candidate

Justification:

Yes

Conclusion:

candidate

Justification:

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

Yes

Conclusion:

Candidate

Justification:

CONCLUSION ON THE STATUS:

Not recommended for listing as an RNQP: This pest/host/intended use combination meets all the criteria for RNQP status but 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.

8 - Tolerance level:

Is there a need to change the Tolerance level:

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;

HOST PLANT N°5: 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:

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?

Conclusion:

Justification:

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:

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;

HOST PLANT N°6: Iris (1IRIG) 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, and EFSA concludes iris is a good and sensitive host plant (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 and sensitivity to infestation of D. destructor in iris 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?

Yes

Justification:

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?

Conclusion:

Justification:

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:

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;

HOST PLANT N°7: Narcissus (1NARG) for the Ornamental sector.

Origin of the listing:

Commission Directive 93/49/EEC

Plants for planting:

Plants intended for planting

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

Conclusion:

Evaluation continues

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

Conclusion:

Not candidate

Justification:

D. destructor attacks a wide range of ornamental and vegetable species, however EFSA quotes only one reference, as saying "authors mention bulb nematode of Iris, Narcissus and hyacinth (indistinguishable morphologically from Ditvlenchus destructor) but the abstract is not conclusive" and concludes "unclear host status" (EFSA-PLH 2016). Therefore it is proposed to conclude Narcissus is not a host and the analysis is concluded at this point.

5 - Economic impact:

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

Justification:

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?

Conclusion:

Justification:

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:

Disqualified: Not enough evidence of the host status. Plants for planting are therefore not considered as a significant pathway for this host.

8 - Tolerance level:

Is there a need to change the Tolerance level:

Proposed Tolerance levels:

Delisting.

9 - Risk management measures:

Is there a need to change the Risk management measure:

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 12, 3834;
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, 4602;
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;

HOST PLANT N°8: Solanum tuberosum (SOLTU) for the Seed potato sector.

Origin of the listing:

IIA2AWG

Plants for planting:

Plants intended for planting, other than [true] seeds

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:

Justification:

Seed potato infected by D. destructor is crucial for establishment of new field infestations. The soil infection route to potato 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). Even different source of infestation are possible, plants for planting is considered to be the "main" pathway for the pest/host/intended use combination.

5 - Economic impact:

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

Yes

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 the 1950s to 1970s, the potato rot nematode was an important pest of potato in Europe and the USA, but today, as a result of general sanitation measures such as weed control, use of clean planting material and removal of infested tubers from the field, the incidence of D. destructor is low and the nematode is of minor importance. In Eastern Europe, however, it causes serious, local economic damage. In the 1970s, when healthy seed potatoes were planted in infested fields in Sweden, yield losses on potato of 41–70 % due to potato rot nematodes were observed. One of the most severe cases of the progressive dry rot of potato tubers caused by D. destructor was recorded in Estonia in the 1960s, where the degree of infestation on farms ranged from 2 to 9 %, but up to 80–90 % of tubers from some fields became infected during storage. Problems caused by the nematode were alleviated in the 1990s using in vitro cultivated basic potato seed material. However, 10 years later, D. destructor re-appeared as a problem in many locations in Estonia (EFSA, 2014).

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?

Conclusion:

Justification:

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:

Recommended for listing as an RNQP - based on EPPO PM 4 Standard. The Seed potato SEWG supported RNQP status also based on potential impact and the effectiveness of current measures.

8 - Tolerance level:

Is there a need to change the Tolerance level:

Proposed Tolerance levels:

Zero tolerance, on the basis of visual inspection of the tubers.

Justification (if necessary):

The SEWG considered whether to apply a zero tolerance or count the pest in with other dry rot causing organisms. It was noted that symptoms may be seen in the crop in some circumstances and that there are some specific symptoms which can be seen in the tubers.

9 - Risk management measures:

Is there a need to change the Risk management measure:

Yes

Proposed Risk management measure:

Post harvest tuber inspection for each lot with no symptoms seen. Any lots in which Ditylenchus destructor is found may not be marketed as seed potatoes.

Justification (if necessary):

PM 4/28 recommended that the crop should be planted in a plot not known to be infected with D. destructor. The SEWG concluded that the criteria ‘not known to be infected with’ doesn’t give enough guaranties.

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;

HOST PLANT N°9: Tigridia (1TIGG) 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?

Conclusion:

Evaluation continues

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

Conclusion:

Candidate

Justification:

In a literature search, no specific references to impact or yield effects in Tigridia by D. destructor could be found.

5 - Economic impact:

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

Justification:

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?

Conclusion:

Not candidate

Justification:

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:

Disqualified: no specific references to impact or yield effects in Tigridia by D. destructor.

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;

HOST PLANT N°10: 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:

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?

Conclusion:

Justification:

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:

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;