| Legend |
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| Justification for qualification based on EPPO PM 4 Standards |
| Justification for disqualification |
| Additional or non-conclusive information |
| Standard text |
NAME OF THE ORGANISM: Pseudomonas amygdali pv. morsprunorum & P. avellanae pv. morsprunorum {Pseudomonas syringae pv. morsprunorum} (PSDMAM for P. amygdali & PSDMAL for P. avellanae)
GENERAL INFORMATION ON THE PEST
Name as submitted in the project specification (if different):
Pseudomonas syringae pv. mors-prunorum
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?
Yes
Conclusion:
- Candidate: Fruits (including hops) sector
Justification (if necessary):
Various Pseudomonas spp. have been reported to be associated with bacterial canker disease (BCD) in Prunus spp. (for overview see Hulin et al., 2020; Table 1).
Pseudomonas syringae pv. morsprunorum has been split in two groups and renamed (see Hulin et al., 2020):
- P. amygdali pv. morsprunorum (PG03) (formerly P. syringae pv. morsprunorum Race 1, Psm1), and
- P. avellanae pv. morsprunorum (PG01b) (formerly P. syringae pv. morsprunorum Race 2, Psm2).
This RNQP summarysheet covers both taxa.
Pseudomonas syringae pv. morsprunorum has been split in two groups and renamed (see Hulin et al., 2020):
- P. amygdali pv. morsprunorum (PG03) (formerly P. syringae pv. morsprunorum Race 1, Psm1), and
- P. avellanae pv. morsprunorum (PG01b) (formerly P. syringae pv. morsprunorum Race 2, Psm2).
This RNQP summarysheet covers both taxa.
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):
Czech Republic (1996); Denmark (1993); Finland (2011); France (1994); Germany (1993); Greece (1992); Ireland (1993); Italy (1992); Netherlands (1993); Poland (1992); Romania (1992); Sweden (1996)
Conclusion:
Justification (if necessary):
Data of the presence of this pest on the EU territory are available in EPPO Global Database (https://gd.eppo.int/).
HOST PLANT N°1: Prunus armeniaca (PRNAR) 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:
Evaluation continues
Justification (if necessary):
Inspection for 'Pseudomonas syringae pv. morsprunorum' is recommended in EPPO Standard PM 4-30 Certification scheme for almond, apricot, peach and plum. However, in the responses to the questionnaire, DE and FR supported deregulation; DE arguing that feasible and effective measures were not available. FR considered that, if not deregulated, thresholds should be adapted. Evaluation continues on the measures.
Remark: The assessment performed covers the given host species as well as interspecific hybrids with other Prunus species.
Remark: The assessment performed covers the given host species as well as interspecific hybrids with other Prunus species.
4 - Are the listed plants for planting the main* pathway for the "pest/host/intended use" combination? (*: significant compared to others):
No
Conclusion:
Not candidate
Justification:
Only Prunus spp. are considered to be significant hosts of Pseudomonas syringae pv. morsprunorum.
P. syringae pv. morsprunorum overwinters in cankers and other diseased tissues, in contaminated buds and occasionally in the tree's vascular system. In spring, bacteria associated with overwintering sites are disseminated by splashing rain on to blossoms, fruits and leaves. Bacteria in dormant buds colonize blossoms and leaves as they unfold. Epiphytic populations of P. syringae pv. morsprunorum develop on the surface of symptomless blossoms and leaves from bloom through to leaf fall in the autumn (Crosse, 1966; Hattingh et al., 1989; cited from CABI, 2021).
Outbreaks of bacterial canker are often associated with prolonged periods of cold, frosty, wet weather late in the spring or with severe storms that injure the emerging blossoms and leaves. Freezing can predispose blossoms and new leaves to infection; the infection is aided by wet weather during the thawing process. Young fruit are infected by bacteria spread in water from new infections and from foliage with epiphytic bacteria. Leaf infection can occur following violent storms with rain in late spring and early summer. Once pv. morsprunorum enters through stomata of the leaf, it can migrate to other regions of the leaf and tree in the vascular system (Roos & Hattingh, 1987, cited from CABI, 2021). Symptoms appear about 5 days later at temperatures between 21 and 26°C (Sundin et al., 1988). After leaves abscise in autumn, the bacteria can enter and infect the tree through fresh leaf scars (Crosse, 1956, 1957; Hignett, 1974; Sundin et al., 1988; cited from CABI, 2021).
P syringae is not common in nurseries (UC PMG, 2017).
Considering its very widespread distribution, the Fruit SEWG concluded that plants for planting was not a significant pathway compared to natural spread.
P. syringae pv. morsprunorum overwinters in cankers and other diseased tissues, in contaminated buds and occasionally in the tree's vascular system. In spring, bacteria associated with overwintering sites are disseminated by splashing rain on to blossoms, fruits and leaves. Bacteria in dormant buds colonize blossoms and leaves as they unfold. Epiphytic populations of P. syringae pv. morsprunorum develop on the surface of symptomless blossoms and leaves from bloom through to leaf fall in the autumn (Crosse, 1966; Hattingh et al., 1989; cited from CABI, 2021).
Outbreaks of bacterial canker are often associated with prolonged periods of cold, frosty, wet weather late in the spring or with severe storms that injure the emerging blossoms and leaves. Freezing can predispose blossoms and new leaves to infection; the infection is aided by wet weather during the thawing process. Young fruit are infected by bacteria spread in water from new infections and from foliage with epiphytic bacteria. Leaf infection can occur following violent storms with rain in late spring and early summer. Once pv. morsprunorum enters through stomata of the leaf, it can migrate to other regions of the leaf and tree in the vascular system (Roos & Hattingh, 1987, cited from CABI, 2021). Symptoms appear about 5 days later at temperatures between 21 and 26°C (Sundin et al., 1988). After leaves abscise in autumn, the bacteria can enter and infect the tree through fresh leaf scars (Crosse, 1956, 1957; Hignett, 1974; Sundin et al., 1988; cited from CABI, 2021).
P syringae is not common in nurseries (UC PMG, 2017).
Considering its very widespread distribution, the Fruit SEWG concluded that plants for planting was not a significant pathway compared to natural spread.
5 - Economic impact:
Are there documented reports of any economic impact on the host?
Justification:
Losses from P. syringae pv. morsprunorum are less severe than those from P. syringae pv. syringae, in part because pv. morsprunorum has a more restrictive host range and geographic distribution than pathovar syringae. The killing of buds, fruiting spurs and branches, and infection of fruits reduces yields. The impact of sporadic disease outbreaks can last for several years due to the time required for infected trees to replace lost bearing surface. Infection of young trees may cause tree mortality or adversely affect tree form (CABI, 2021).
Although P. syringae pv. morsprunorum is widely distributed, absence of the bacterium may be an important consideration for stone fruit-growing areas where the bacterium does not (yet) occur. The bacterium would not be expected to represent a serious risk for areas where bacterial canker, caused by P. syringae pv. syringae, already exists (CABI, 2021).
Bacterial canker of apricots is an important disease in regions of production with cold winters and conducive soils (Parisi et al. 2019). The disease is worse in low, gravelly, sandy spots, soils with shallow claypans, or other soil conditions that lead to weakened growth. vigorous trees are less susceptible to bacterial canker, while young trees (2–8 years old) are most affected. The disease rarely occurs in the first year of planting unless the ground is not fumigated before planting. It is uncommon in nurseries (UC ARN, 2017).
Both Pseudomonas amygdali pv. morsprunorum (Psm1) and P. avellanae pv. morsprunorum (Psm2) have been reported to induce canker, dieback, necrosis on leaves, fruit and blossom on Prunus armeniaca, for Psm1 is had been confirmed by controlled pathogenicity tests (see Table 1 Hulin et al. 2020).
Although P. syringae pv. morsprunorum is widely distributed, absence of the bacterium may be an important consideration for stone fruit-growing areas where the bacterium does not (yet) occur. The bacterium would not be expected to represent a serious risk for areas where bacterial canker, caused by P. syringae pv. syringae, already exists (CABI, 2021).
Bacterial canker of apricots is an important disease in regions of production with cold winters and conducive soils (Parisi et al. 2019). The disease is worse in low, gravelly, sandy spots, soils with shallow claypans, or other soil conditions that lead to weakened growth. vigorous trees are less susceptible to bacterial canker, while young trees (2–8 years old) are most affected. The disease rarely occurs in the first year of planting unless the ground is not fumigated before planting. It is uncommon in nurseries (UC ARN, 2017).
Both Pseudomonas amygdali pv. morsprunorum (Psm1) and P. avellanae pv. morsprunorum (Psm2) have been reported to induce canker, dieback, necrosis on leaves, fruit and blossom on Prunus armeniaca, for Psm1 is had been confirmed by controlled pathogenicity tests (see Table 1 Hulin et al. 2020).
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:
Planting trees that are budded or grafted about 32 inches above the root crown can help suppress bacterial canker infections. Bacterial canker tends to mostly affect weak trees, so any management practice that improves tree vigour (e.g., lighter, more frequent irrigation, improved tree nutrition, nematode management, etc.) will help to reduce the incidence of this disease (UC PMG, 2017).
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: plants for planting is not considered to be a significant pathway compared to natural spread.
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:
- CABI (2021) Pseudomonas syringae pv. morsprunorum (bacterial canker of stone fruits) (accessed 12/Aug/2024). CABI Compendium. https://doi.org/10.1079/cabicompendium.44978.
- Crosse JE (1956). Bacterial canker of stone-fruits. II. Leaf scar infection of cherry. Journal of Horticultural Science 31, 212-224.
- Crosse JE (1957) Bacterial canker of stone-fruits. III. Inoculum concentration and time of inoculations in relation to leaf-scar infection of cherry. Annuals of Applied Biology 45, 19-35.
- Crosse JE (1966) Epidemiological relations of the Pseudomonad pathogens of deciduous fruit trees. Annual Review of Phytopathology 4, 291-310.
- Hattingh MJ, Roos IMM & Mansvelt EL (1989) Infection and systemic invasion of deciduous fruit trees by Pseudomonas syringae in South Africa. Plant Disease 73(10), 784-789.
- Hignett RC (1974). Absorption of Pseudomonas morsprunorum through cherry leaf scars. Journal of General Microbiology 80(2), 501-506.
- Hulin MT, Jackson RW, Harrison RJ & Mansfield JW (2020). Cherry picking by pseudomonads: After a century of research on canker, genomics provides insights into the evolution of pathogenicity towards stone fruits. Plant Pathology 69(6), 962-978. doi: 10.1111/ppa.13189.
- Latorre BA, Jones AL, 1979. Evaluation of weeds and plant refuse as potential sources of inoculum of Pseudomonas syringae in bacterial canker of cherry. Phytopathology, 69(10):1122-1125.
- Parisi L, Morgaint B, Blanco‐Garcia J, Guilbaud C, Chandeysson C, Bourgeay JF, Moronvalle A, Brun L, Brachet ML & Morris, C. E. (2019). Bacteria from four phylogroups of the Pseudomonas syringae complex can cause bacterial canker of apricot. Plant Pathology 68(7), 1249-1258. https://bsppjournals.onlinelibrary.wiley.com/doi/pdfdirect/10.1111/ppa.13051
- Roos IMM & Hattingh MJ (1987b). Systemic invasion of cherry leaves and petioles by Pseudomonas syringae pv. morsprunorum. Phytopathology 77(9), 1246-1252.
- Sundin GW, Jones AL & Olson BD (1988). Overwintering and population dynamics of Pseudomonas syringae pv. syringae and P.s. pv. morsprunorum on sweet and sour cherry trees. Canadian Journal of Plant Pathology 10(4), 281-288.
- UC PMG (2017) Bacterial canker. In Pest management guidelines – Apricot. Publication 3433. University of California Agriculture and Natural Resources, pages 59-60