| 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: Podosphaera mors-uvae {Sphaerotheca mors-uvae} (SPHRMU)
GENERAL INFORMATION ON THE PEST
Name as submitted in the project specification (if different):
Pest category:
Fungi
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):
Powdery mildew of gooseberries is a foliar disease caused by Podosphaera mors-uvae in Europe, North America, Australia, New Zealand and Asia (Picton and Hummer, 2003; Plantwiseplus Knowledge Bank, 2019). In particular, in the European Union, the pest is reported in Austria, Belgium, Bulgaria, Czechia, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Ireland, Latvia, Lithuania, Netherlands, Poland, Portugal, Romania (Purnell and Sivanesan, 1970; Wennekera, 2016; CABI, 2019), Sweden (CABI, 2019).
HOST PLANT N°1: Ribes (1RIBG) 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):
In EPPO Standard PM 4/9 Certification scheme for Ribes, plants should be grown in individual pots in a sterilized growing medium, with strict precautions, including preventive treatments as appropriate, against infestation by […], powdery mildews (Sphaerotheca mors-uvae) […]. In responses to the consultation about draft recommendations for RNQP Project part 2, ES supported deregulation in the EU, considering that planting is not a significant pathway. Evaluation continues on this 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:
Sphaerotheca mors-uvae attacks gooseberry (Ribes uva-crispa) and black currants (Ribes nigrum) causing serious infections (Wennekera, 2016). Other Ribes species are reported as host plants (Purnell and Sivanesan, 1970).
The fungus is spread by spores (Wennekera, 2016).
The fungus overwinters on shoot twigs and during the spring and summer it infects leaves, shoots tips and fruits (Vagiri, 2012).
Considering its biology, its wide distribution and its mode of dispersal (wind-borne spores), plants for planting are not a significant pathway for its dissemination compared to natural spread.
Similarly, for another closely related species with similar biology, Podosphaera aphanis, the Fruit SEWG considered that plants for planting aren’t a significant pathway compared to wind-borne transmission from other hosts in the environment, concluding its disqualification as RNQP of Fragaria, even under tunnels or glasshouses which need airflow.
The fungus is spread by spores (Wennekera, 2016).
The fungus overwinters on shoot twigs and during the spring and summer it infects leaves, shoots tips and fruits (Vagiri, 2012).
Considering its biology, its wide distribution and its mode of dispersal (wind-borne spores), plants for planting are not a significant pathway for its dissemination compared to natural spread.
Similarly, for another closely related species with similar biology, Podosphaera aphanis, the Fruit SEWG considered that plants for planting aren’t a significant pathway compared to wind-borne transmission from other hosts in the environment, concluding its disqualification as RNQP of Fragaria, even under tunnels or glasshouses which need airflow.
5 - Economic impact:
Are there documented reports of any economic impact on the host?
Yes
Justification:
On susceptible cultivars, the symptoms of the disease are characterized by white powdery growths on surface of leaves and young green shoots. Scorch like symptoms appear on the leaves that become deformed and dry out. The infected leaves may fall off during warm weather and infected plants have a stunted growth. The severely affected fruits develop a dark brown, felt-like coating that renders the fruits unmarketable (Vagiri, 2012).
First recorded on gooseberries (R. grossularia) in 1900 in Ireland, the fungus has been a major limiting factor for successful production of gooseberries (Vagiri, 2012).There are reports of its significant economic impact in different growing regions, including China (Li et al., 2024), USA (Picton and Hummer, 2003) and Denmark (Pedersen and Toldam-Andersen, 2004).
The Fruit SEWG commented that in the bibliography there are reports about significant impact, but the scientific work often deals with traditional non-resistant or tolerant varieties, and the benefit of the newly bred varieties is not taken into account. Protection against the powdery mildew of small fruits is one of the main goals during the breeding, so the new varieties are practically all resistant or highly tolerant.
First recorded on gooseberries (R. grossularia) in 1900 in Ireland, the fungus has been a major limiting factor for successful production of gooseberries (Vagiri, 2012).There are reports of its significant economic impact in different growing regions, including China (Li et al., 2024), USA (Picton and Hummer, 2003) and Denmark (Pedersen and Toldam-Andersen, 2004).
The Fruit SEWG commented that in the bibliography there are reports about significant impact, but the scientific work often deals with traditional non-resistant or tolerant varieties, and the benefit of the newly bred varieties is not taken into account. Protection against the powdery mildew of small fruits is one of the main goals during the breeding, so the new varieties are practically all resistant or highly tolerant.
What is the likely economic impact of the pest irrespective of its infestation source in the absence of phytosanitary measures? (= official measures)
Minor to Medium
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:
Impact is dependant on growing practices and resistance.
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:
Justification:
A range of resistance genes for powdery mildew has been identified in black currant varieties. Control of mildew is otherwise dependent on the use of plant protection products, but continued breeding for durable resistance in black currant cultivars could successfully limit the possibility of the disease and thus lower production costs (Vagiri, 2012).
7- Is the quality of the data sufficient to recommend the pest to be listed as a RNQP?
Conclusion:
Justification:
The data are enough to make a decision
CONCLUSION ON THE STATUS:
Disqualified: plants for planting is not considered to be a significant pathway compared to others.
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 (2019) Datasheet for Podosphaera mors-uvae (powdery mildew of currant). CABI Compendium 50925. Available at https://www.cabidigitallibrary.org/doi/full/10.1079/cabicompendium.50925
- Li W,Qin D, Ma R, Li S & Wang L (2024) Comparative evaluation of physiological and molecular responses of blackcurrant varieties to powdery mildew infection. Front. Plant Sci. 15:1445839. doi: 10.3389/fpls.2024.1445839
- Natal'ina OB, Gor'kovenko VS, Puzanova LA, 1981 . Powdery mildew of black and red currants in the Krasnodar region. (Muchnistaya rosa chernoi i krasnoi smorostiny v Krasnodarskom krae.) Mikologiya i Fitopatologiya 15(6), 513-514.
- Pedersen HL & Toldam-Andersen TB (2004) Yield reduction in black currants due to infections of American gooseberry mildew. Acta Horticulturae 649, 259-264.
- Picton DD & Hummer KE (2003) Control of powdery mildew on leaves and stems of gooseberry. HorTechnology, 13(2), 365-367.
- Purnell TJ & Sivanesan A (1970) Sphaerotheca mors-uvae. CMI Descriptions of Plant Pathogenic Fungi and Bacteria, No. 254. Surrey, England: Commonwealth Mycological Institute (ABSTRACT)
- Plantwiseplus Knowledge Bank (2019) Podosphaera mors-uvae (powdery mildew of currant). https://doi.org/10.1079/pwkb.species.50925
- Vagiri M (2012) Black currant (Ribes nigrum L.) – an insight into the crop. A synopsis of a PhD study. Swedish University of Agricultural Sciences.
- Wennekera M (2016) Controlling powdery mildew (Sphaerotheca mors-uvae) of gooseberry (Ribes uva-crispa) with potassium bicarbonate and risk of phytotoxicity. Acta Hortic. 1133. Proc. XI Int. Rubus and Ribes Symp. DOI 10.17660/ActaHortic.2016.1133.81