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Justification for qualification based on EPPO PM 4 Standards
Justification for disqualification
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NAME OF THE ORGANISM: Pear bark necrosis agent (PRBN00)

GENERAL INFORMATION ON THE PEST

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

Pear bark necrosis agent (bark necrosis)

Pest category:

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: Fruits (including hops) 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:

Not candidate: Fruits (including hops) sector

Justification (if necessary):

Note on taxonomy: Pear bark necrosis disease was first described by Kegler (1967). Since two types of symptoms were reported, it is still not clear whether one or two agents evoke the symptoms (Nemeth, 1986). Therefore, pear bark necrosis agent would be an appropriate name. Field indexing using woody indexing (Jelkmann, 2004) would be needed for detection and identification. NB. Quince bark necrosis was evoked after graft-inoculation of quince with three isolates of apple rubbery (Cropley et al., 1963), a disease of unknown aetiology.
There are several old accounts in literature about bark disorders affecting pear trees, each with a different name: pear blister canker (Cropley, 1960), pear rough bark (Thomsen, 1961), pear bark split and necrosis (Kegler, 1967; Kegler et al., 1968), and pear bark measles (Cordy & MacSwan, 1961). Because they were reported in different pear cultivars and because these agents remain poorly defined, it is difficult to ascertain whether they indeed correspond to different diseases (Flores et al., 2011).

Pear bark necrosis agent does not fulfill the requirement of identity and should therefore not be listed as an RNQP.
[Remark: LT and NL did not support recommendation for regulation of pear bark necrosis agent as an RNQP since no information is available yet on causal agents. DE indicated that pear bark necrosis agent was also listed as an RNQP in CH and GB]

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):

Conclusion:

Justification (if necessary):

HOST PLANT N°1: Cydonia oblonga (CYDOB) for the Fruits (including hops) sector.

Origin of the listing:

Commission Implementing Directive (EU) 2014/98/EU and Commission Implementing Regulation (EU) 2019/2072

Plants for planting:

Plants intended for planting

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

Yes

Conclusion:

Justification (if necessary):

Testing for 'bark necrosis' recommended in EPPO Standard PM 4-27 Pathogen-tested material of Malus, Pyrus and Cydonia, for Pyrus and Cydonia.' In the preliminary excel file submitted by the European Commission, one country highlighted that the causal agents would need to be defined and that little information in available on epidemiology. It was proposed as a candidate for delisting.

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

Conclusion:

Justification:

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?

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: no clear taxonomy

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:

Cropley R (1960) Pear blister canker: a virus disease. Annual Report East Mailing Research Station for 1959 43, 104.
Cropley R (1963) Blister canker of pear. In Virus diseases of apples and pears (ed AF Posnette). Technical Communication No. 30. Commonwealth Bureau of Horticulture and Plantation Crops, East Malling, Maidstone, Kent, UK, pp 103-106.
Cropley R, Wolfswinkel LD & Posnette AF (1963) The identification of some viruses infecting apple, pear and quince. Proceedings 5th European Symposium Fruit Tree Virus Diseases, in Phytpathologia mediterranea 2, 132-136.
Cordy CD & MacSwan JC (1961). Some evidence that pear bark measles is seed-borne. Plant Disease Reporter 45, 891.
Desvignes JC, Cornaggia D, Grasseau N, Ambros S & Flores R (1999) Pear blister canker viroid: host range and improved bioassay with two new pear indicators, Fieud 37 and Fieud 110. Plant Disease 83(5), 419-422.
Kegler H (1967) Der Viröse Birnenverfall, die Rindenrissigkeit und die Rindennekrose. Obstbau 7, 21-23.
Kegler H, Schmidt HE & Schimanski HH (1968) Der Nachweis weiterer Viruskrankheiten an Obstgehölzen in der Deutschen Demokratischen Republik. Nachrichtenblatt des Deutschen Pflanzenschutzdienst (Berlin), 22, 168-175
Nemeth M (1986) Pear bark necrosis. In Virus, Mycoplasma and Rickettsia Diseases (ed Nemeth M). Martinus Nijhoff Publishers, Dordrecht, The Netherlands, pp 223-225.
Flores R, Ambrós S, Llácer G & Hernández (2011) Pear blister canker viroid (Chapter 13). In Virus and Virus-Like Diseases of Pome and Stone Fruits (eds Hadidi A, Barba M, Candresse T & Jelkmann W). American Phytopathological Society, St Paul, MN, USA. pp 63-66.
Jelkmann W (2004) Detection of virus and virus-like diseases of fruit trees: laboratory assays, bioassays and indicators. Acta Horticulturae 657, 575-596.
Nemeth M (1986) Pear blister canker. In Virus, Mycoplasma and Rickettsia Diseases. Martinus Nijhoff Publishers, Dordrecht, The Netherlands (ed Nemeth M), pp 226-228.
Ronde Kristensen H (1963) Rough bark op pear. In Virus diseases of apples and pears (ed AF Posnette). Technical Communication No. 30. Commonwealth Bureau of Horticulture and Plantation Crops, East Malling, Maidstone, Kent, UK, pp 107-108.
Thomsen A (1961) Split bark of pears (rough bark of pears). Tidsskrift for Planteavl 65, 69-72.