| Legend |
|---|
| Justification for qualification based on EPPO PM 4 Standards |
| Justification for disqualification |
| Additional or non-conclusive information |
| Standard text |
NAME OF THE ORGANISM: Candidatus Phlomobacter fragariae (PHMBFR)
GENERAL INFORMATION ON THE PEST
Name as submitted in the project specification (if different):
Candidatus Phlomobacter fragariae (Phlomobacter fragariae)
Pest category:
Bacteria
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: 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:
- Candidate: Fruits (including hops) sector
Justification (if necessary):
2 – Status in the EU:
Is this pest already a quarantine pest for the whole EU?
No
Presence in the EU:
Yes
List of countries (EPPO Global Database):
-
Conclusion:
Candidate
Justification (if necessary):
France (Zreik et al, 1998). Remark: the pest is also regulated as an RNQP in the United-Kigdom and Switzerland, so assumed to be present.
HOST PLANT N°1: Fragaria (1FRAG) 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?
No
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:
Planthopper Cixius wagneri is the vector of Ca. Phlomobacter fragariae (Danet et al., 2003).
The role of plants for planting may be limited: from the first description in south-western France (Zreik et al, 1998) it was also found in Japan (Tanaka et al., 2006), but no further reports in other regions (CAB abstract search, 19/Mar/2024). In addition Ca. Phlomobacter fragariae was predominantly found in production fields, whereas another disease – stolbur – was mainly found in the nurseries; indicating that the planthopper is infecting the plants in the field (Danet et al., 2003). However, following the initial infection via the insect, Ca. Phlomobacter fragariae can be transmitted to the next generation via stolons (Dittmer et al., 2021).
In Italy, another bacteria-like organism (BLO) caused marginal chlorosis symptoms (Terlizzi et al., 2007). This BLO is more closely related to “syndrome basses richesses” (SBR) in sugar beet than to Ca. Phlomobacter fragariae. For this BLO causing strawberry marginal chlorosis (SMC) and SBR disease a new name was proposed in Bressan et al. (2011): 'Candidatus Arsenophonus phytopathogenicus'. This pathogen is vectored by Pentastiridius leporinus (in Dittmer et al., 2021).
[Remark: When responding to the questionnaire, PL considered that plants for planting was not the main pathway.]
The Fruit SEWG considered that there was uncertainty whether plants for planting was the main pathway under outdoor conditions (It remains unclear whether Cixius wagneri, which has only one generation a year, develops from eggs on strawberry and uses strawberry as a regular feeding source). However, the experts considered that when production occurs in tunnels or under protected conditions, plants for planting is a significant pathway compared to others.
The role of plants for planting may be limited: from the first description in south-western France (Zreik et al, 1998) it was also found in Japan (Tanaka et al., 2006), but no further reports in other regions (CAB abstract search, 19/Mar/2024). In addition Ca. Phlomobacter fragariae was predominantly found in production fields, whereas another disease – stolbur – was mainly found in the nurseries; indicating that the planthopper is infecting the plants in the field (Danet et al., 2003). However, following the initial infection via the insect, Ca. Phlomobacter fragariae can be transmitted to the next generation via stolons (Dittmer et al., 2021).
In Italy, another bacteria-like organism (BLO) caused marginal chlorosis symptoms (Terlizzi et al., 2007). This BLO is more closely related to “syndrome basses richesses” (SBR) in sugar beet than to Ca. Phlomobacter fragariae. For this BLO causing strawberry marginal chlorosis (SMC) and SBR disease a new name was proposed in Bressan et al. (2011): 'Candidatus Arsenophonus phytopathogenicus'. This pathogen is vectored by Pentastiridius leporinus (in Dittmer et al., 2021).
[Remark: When responding to the questionnaire, PL considered that plants for planting was not the main pathway.]
The Fruit SEWG considered that there was uncertainty whether plants for planting was the main pathway under outdoor conditions (It remains unclear whether Cixius wagneri, which has only one generation a year, develops from eggs on strawberry and uses strawberry as a regular feeding source). However, the experts considered that when production occurs in tunnels or under protected conditions, plants for planting is a significant pathway compared to others.
5 - Economic impact:
Are there documented reports of any economic impact on the host?
Yes
Justification:
Marginal chlorosis has been reported in strawberry production fields in south-western France with an incidence of a few plants to nearly 100% of plants in some production tunnels (Danet et al., 2003). It can still be found in production fields (Danet 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?
No
Conclusion:
Justification:
Unclear, no recent data on impact. The Fruit SEWG considered that this was not clear whether only this pest was causing the reported damage. Etiology of the disease is not considered clear enough and more studies would be needed.
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?
Yes
Conclusion:
Candidate
Justification:
Special segregation of nursery and production regions (Dittmer et al., 2021): the strawberry propagation material should be isolated from the fruit production facilities and from sugar beet fields. The problem of vector transmission (Cixius wagneri) where fragaria material and sugar beet are produced (ongoing research investigations) maybe solved with production under tunnel propagating facilities and in vitro conditions.
7- Is the quality of the data sufficient to recommend the pest to be listed as a RNQP?
No
Conclusion:
Candidate by default
Justification:
Etiology of the disease is not considered clear enough. More studies are needed on the economic impact.
CONCLUSION ON THE STATUS:
Recommended for listing as an RNQP, by default (etiology of the disease is not considered clear enough; more studies on economic impact are needed). Conclusion was that there is insufficient evidence to recommend changes from the current regulation and measures.
8 - Tolerance level:
Is there a need to change the Tolerance level:
No
Proposed Tolerance levels:
9 - Risk management measures:
Is there a need to change the Risk management measure:
No
Proposed Risk management measure:
REFERENCES:
- Bressan A, Terlizzi F & Credi R. (2012). Independent origins of vectored plant pathogenic bacteria from arthropod-associated Arsenophonus endosymbionts. Microbial Ecology 63, 628–638. DOI 10.1007/s00248-011-9933-5
- Danet JL, Foissac X, Zreik L, Salar P, Verdin E, Nourrisseau JG & Garnier M (2003). “Candidatus Phlomobacter fragariae” is the prevalent agent of marginal chlorosis of strawberry in French production fields and is transmitted by the planthopper Cixius wagneri (China). Phytopathology 93, 644-649.
- Danet JL, Fimbeau S, Salar P, Faure C, Pommier JJ, Turquet M, Marais A, Foissac X (2012) Strawberry marginal chlorosis (SMC): a disease of various bacterial and viral etiologies in France. Petria 22(3), 307 (22nd ICVF).
- Dittmer J, Lusseau T, Foissac X, Faoro F (2021). Skipping the insect vector: plant stolon transmission of the phytopathogen ‘Ca. Phlomobacter fragariae’ from the Arsenophonus clade of insect endosymbionts. Insects 12, 93. https://doi.org/10.3390/insects12020093.
- Tanaka M, Nao M, Usugi T (2006) Occurrence of strawberry marginal chlorosis caused by “Candidatus
- Phlomobacter fragariae” in Japan. Journal of General Plant Pathology 72, 374–377. DOI 10.1007/s10327-006-0308-6
- Terlizzi F, Babini AR, Lanzoni C, Pisi A, Credi R, Foissac X & Salar P (2007). First Report of a γ 3-Proteobacterium Associated with Diseased Strawberries in Italy. Plant Disease 91: 1688. http://dx.doi.org/10.1094/PDIS-91-12-1688B.
- Zreik L, Bove JM & Garnier M (1998). Phylogenetic characterization of the bacterium-like organism associated with marginal chlorosis of strawberry and proposition of a Candidatus taxon for the organism, 'Candidatus Phlomobacter