| Legend |
|---|
| Justification for qualification based on EPPO PM 4 Standards |
| Justification for disqualification |
| Additional or non-conclusive information |
| Standard text |
NAME OF THE ORGANISM: Pseudomonas savastanoi pv. savastanoi (PSDMSA)
GENERAL INFORMATION ON THE PEST
Name as submitted in the project specification (if different):
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):
Pseudomonas savastanoi comprises of five different pathovars of woody hosts:
- P. savastanoi pv. savastanoi (olive, Olea europaea),
- P. savastanoi pv. nerii (oleander, Nerium oleander),
- P. savastanoi pv. fraxini (ash, Fraxinus excelsior),
- P. savastanoi pv. retacarpa (yellow broom, Retama sphaerocarpa) and
- P. savastanoi pv. mandevillae (Mandevila spp.).
These pathovars produce knots (P. savastanoi pv. savastanoi, pv. nerii and pv. retacarpa), excrescences (P. savastanoi pv. fraxini) and necrotic spots on leaves and knot formation on stems (P. savastanoi pv. mandevilliae) (Caballo-Ponce et al., 2021). Although the pathovars show differences in host range, several are able to induce knots in olive: P. savastanoi pv. savastanoi, pv. nerii, pv. fraxini and pv. mandevillae (Ramos et al., 2012; Moreno-Pérez et al., 2020; Caballo-Ponce et al., 2021). Here was focused on the disease aspect “olive knot”.
- P. savastanoi pv. savastanoi (olive, Olea europaea),
- P. savastanoi pv. nerii (oleander, Nerium oleander),
- P. savastanoi pv. fraxini (ash, Fraxinus excelsior),
- P. savastanoi pv. retacarpa (yellow broom, Retama sphaerocarpa) and
- P. savastanoi pv. mandevillae (Mandevila spp.).
These pathovars produce knots (P. savastanoi pv. savastanoi, pv. nerii and pv. retacarpa), excrescences (P. savastanoi pv. fraxini) and necrotic spots on leaves and knot formation on stems (P. savastanoi pv. mandevilliae) (Caballo-Ponce et al., 2021). Although the pathovars show differences in host range, several are able to induce knots in olive: P. savastanoi pv. savastanoi, pv. nerii, pv. fraxini and pv. mandevillae (Ramos et al., 2012; Moreno-Pérez et al., 2020; Caballo-Ponce et al., 2021). Here was focused on the disease aspect “olive knot”.
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):
HOST PLANT N°1: Olea europaea (OLVEU) 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):
EPPO Standard PM 4/17 Certification scheme for olive trees and rootstock recommends visual examination to prevent infection with Pseudomonas savastonoi pv. savastonoi. However, in the responses to the questionnaire, PL and SI supported deregulation in the EU considering that plants for planting was not the main pathway and that economic impact was acceptable. Evaluation continues on these two criteria.
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:
Pseudomonas savastanoi pv. savastanoi is a pathogen of olive and is present in all olive-growing areas in the world. The bacterial disease can be transported over indefinitely long distances in infected propagation material. Olive knot can become established in a new area if diseased plants are introduced and not promptly eradicated (CABI, 2021).
Once established, the main sources of P. savastanoi pv. savastanoi inoculum are bacteria oozing from cracks in knots, or epiphytic bacteria on host plants. The short distance spread of inoculum is mainly mediated by wind-driven rain, but agricultural practices such as pruning, grafting, and fruit harvesting can also contribute to local spread. Insects may have a significant role in the dispersal of the pathogen, but evidence of this is lacking or contradictory (CABI, 2021).
Olive knot disease incidence is generally correlated with rainfall and is more severe in higher rainfall areas or during years of high rainfall. They are readily spread by water at all times of the year. Bacteria survive in galls and as epiphytes on leaves and twigs. As an epiphyte they may be spread on asymptomatic plant tissue. Infection occurs in fall, winter, and spring. The knots develop in late spring when trees resume growth and continue to develop through summer. Openings are necessary for penetration of bacteria, and these are provided by leaf scars, pruning wounds, or bark cracks made by freezing. Freeze injury can lead to disease epidemics because the resulting defoliation and bark splitting normally occur during the winter when rain occurs and can spread the disease (UC IPM, 2014).
[In the responses to the questionnaire, SI commented that 'Bacteria can spread over long distances from infected trees. Planting of uninfected material seems pointless if infected trees are in vicinity'.]
Considering its widespread presence in the EU, the Fruit SEWG concluded that plants for planting was not a significant pathway compared to natural spread in most situations. Locally, e.g. in Spain where many vineyards are removed in the recent years to plant olive orchards due to the increase in olive oil prices, plants for planting may become a significant pathway. However, asymptomatic testing was considered not to be cost-effective as this would only serve to protect limited new olive production areas. The general ‘substantially free from‘ requirement on traded material was considered enough for this pest.
Once established, the main sources of P. savastanoi pv. savastanoi inoculum are bacteria oozing from cracks in knots, or epiphytic bacteria on host plants. The short distance spread of inoculum is mainly mediated by wind-driven rain, but agricultural practices such as pruning, grafting, and fruit harvesting can also contribute to local spread. Insects may have a significant role in the dispersal of the pathogen, but evidence of this is lacking or contradictory (CABI, 2021).
Olive knot disease incidence is generally correlated with rainfall and is more severe in higher rainfall areas or during years of high rainfall. They are readily spread by water at all times of the year. Bacteria survive in galls and as epiphytes on leaves and twigs. As an epiphyte they may be spread on asymptomatic plant tissue. Infection occurs in fall, winter, and spring. The knots develop in late spring when trees resume growth and continue to develop through summer. Openings are necessary for penetration of bacteria, and these are provided by leaf scars, pruning wounds, or bark cracks made by freezing. Freeze injury can lead to disease epidemics because the resulting defoliation and bark splitting normally occur during the winter when rain occurs and can spread the disease (UC IPM, 2014).
[In the responses to the questionnaire, SI commented that 'Bacteria can spread over long distances from infected trees. Planting of uninfected material seems pointless if infected trees are in vicinity'.]
Considering its widespread presence in the EU, the Fruit SEWG concluded that plants for planting was not a significant pathway compared to natural spread in most situations. Locally, e.g. in Spain where many vineyards are removed in the recent years to plant olive orchards due to the increase in olive oil prices, plants for planting may become a significant pathway. However, asymptomatic testing was considered not to be cost-effective as this would only serve to protect limited new olive production areas. The general ‘substantially free from‘ requirement on traded material was considered enough for this pest.
5 - Economic impact:
Are there documented reports of any economic impact on the host?
Justification:
Olive knot can girdle and kill trees if infections occur on the trunks of young trees. On older trees, it reduces productivity by girdling twigs and branches and causes dieback. Infection is also associated with an off-flavor of the fruit (UC PMG, 2014). Schroth et al. (1973) reported that olive plants with moderate infections (0.5-1 knots/ft (about 30 cm) of fruitwood) had smaller fruits and 28% lower fruit production than slightly infected plants (0.1-0.3 knots/ft of fruitwood), with a consequent reduction in farm income.
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:
Olive is the most important economic host. Dependent on the pathovar involved in symptoms development, other hosts like oleander and ash might be susceptible and develop symptoms.
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:
Whole plants or plant parts (i.e. cuttings, buds, etc.) showing knots are easily recognized and discarded in nursery practice. However, bacterial populations of P. savastanoi pv. savastanoi on the phylloplane and as latent and systemic infections make highly dubious the practice of permitting the transfer of plants cleared by inspection to be moved to disease-free localities (CABI, 2021)
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 a significant pathway compared to natural spread. The pathogen is present in all growing areas in the world.
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:
- Caballo-Ponce E, Pintado A, Moreno-Pérez A, Murillo J, Smalla K & Ramos C (2021). Pseudomonas savastanoi pv. mandevillae pv. nov., a clonal pathogen causing an emerging, devastating disease of the ornamental plant Mandevilla spp. Phytopathology 111, 1277-1288. https://doi.org/10.1094/PHYTO-11-20-0526-R
- CABI (2021) Pseudomonas savastanoi pv. savastanoi (oleander knot). CABI ditigial datasheet. https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.45004. (Accessed 09/Aug/2024).
- Moreno-Pérez A, Pintado A, Murillo J, Caballo-Ponce E, Tegli S, Moretti C, Rodríguez-Palenzuela P & Ramos C (2020) Host Range Determinants of Pseudomonas savastanoi pathovars of woody hosts revealed by comparative genomics and cross-pathogenicity tests. Frontiers in Plant Science 2(11), 973. doi: 10.3389/fpls.2020.00973.
- Ramos C, Matas IM, Bardaji L, Aragón IM & Murillo J (2012) Pseudomonas savastanoi pv. savastanoi: some like it knot. Molecular Plant Pathology 13(9), 998-1009. doi: 10.1111/j.1364-3703.2012.00816.x.
- UC PMG (2014) Olive knot. In Olive, Pest management guidelines for agriculture. University of California Agriculture and Natural Resources, Publication 3452, 39-40. (Accessed 09/Aug/2024). https://ipm.ucanr.edu/legacy_assets/PDF/PMG/pmgolive.pdf.