| Legend |
|---|
| Justification for qualification based on EPPO PM 4 Standards |
| Justification for disqualification |
| Additional or non-conclusive information |
| Standard text |
NAME OF THE ORGANISM: Erysiphe grossulariae {Microsphaera grossulariae} (MCRSGR)
GENERAL INFORMATION ON THE PEST
Name as submitted in the project specification (if different):
Microsphaera grossulariae
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):
Two species of powdery mildew are reported in Ribes spp.:
• European gooseberry mildew (Erysiphe grossulariae, formerly known as Microsphaera grossulariae) and
• American gooseberry mildew (Podosphaera mors-uvae, formerly known as Sphaerotheca mors-uvae). The pathogen reached Europe in 1890, from American gooseberry nursery stock (Smith et al.,1988).
• European gooseberry mildew (Erysiphe grossulariae, formerly known as Microsphaera grossulariae) and
• American gooseberry mildew (Podosphaera mors-uvae, formerly known as Sphaerotheca mors-uvae). The pathogen reached Europe in 1890, from American gooseberry nursery stock (Smith et al.,1988).
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):
Erysiphe grossulariae has been reported in e.g. Czech Republic (Mieslerová et al., 2020), Germany (Jage et al., 2010; Bresinsky, 2016), Poland (Kozłowska et al., 2015)
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):
Listed in Standard PM 4-9 Certification scheme for Ribes as Microsphaera grossulariae. However, in the responses to the questionnaire DE, NL and SI supported deregulation. DE and SI considered that plants for planting was not the main pathway. SI considered that economic impact was acceptable. Evaluation continues on these two criteria. DE added that the pest was easily controlled by producers and that a 'practically free from' requirement would be enough.
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:
Erysiphe grossulariae is monophagous on various Ribes spp.: Ribes alpinum, R. americanum, R. x nidigrolaria, R. nigrum, R. rotundifolium, R. rubrum, R. sanguineum, R. spicatum, and R. uva-crispa (Ellis, 2001-2024).
Erysiphe grossulariae attacks gooseberry and is known as European gooseberry mildew. It is less common than American gooseberry mildew (Podosphaera mors-uvae, formerly known as Sphaerotheca mors-uvae). It is rarely found on currant bushes (Smith et al., 1988).
Unlike those of most other fungi, powdery mildew spores do not require free water for germination. Some species require high humidity, but it is usually provided at the leaf surface when cold nights change to warm days or when plants are grown in crowded, low, or shady locations without sufficient air circulation (Horst, 2001).
Erysiphe grossulariae, like other powdery mildews, is an obligate pathogen, and lives ectoparasitic. It occurs mainly on the upper surfaces of leaves but may occasionally be found on the lower leaf surface or on berries. The mycelium persists throughout the season but always remains thin and scanty. It is usually found on densely planted, shaded bushes. During the vegetation period, the fungus spreads through spores (conidia); these are the inoculum for the repeating secondary cycle. It persists through its resistance mycelium, located under the bud scales, from one year to another. Black cleisthothecia (fungal structures in which the sexual ascospores are produced) may be found fully exposed on the mycelial patches. In autumn, they fall off leaves or drop to the ground with leaves and remain dormant during winter. The main source of infection in the spring is ascospores released from overwintering cleistothecia (Smith et al., 1988; Dickman et al., 1994; Anonymous, 2024).
[In responses to the questionnaire, NL commented that the pest was 'airborne and widespread in nature'.]
The Fruit SEWG considered that once present in an area, natural aerial spread is the main source of infection. Ribes plants for planting, generally propagated as cuttings, are not considered as a significant pathway.
Erysiphe grossulariae attacks gooseberry and is known as European gooseberry mildew. It is less common than American gooseberry mildew (Podosphaera mors-uvae, formerly known as Sphaerotheca mors-uvae). It is rarely found on currant bushes (Smith et al., 1988).
Unlike those of most other fungi, powdery mildew spores do not require free water for germination. Some species require high humidity, but it is usually provided at the leaf surface when cold nights change to warm days or when plants are grown in crowded, low, or shady locations without sufficient air circulation (Horst, 2001).
Erysiphe grossulariae, like other powdery mildews, is an obligate pathogen, and lives ectoparasitic. It occurs mainly on the upper surfaces of leaves but may occasionally be found on the lower leaf surface or on berries. The mycelium persists throughout the season but always remains thin and scanty. It is usually found on densely planted, shaded bushes. During the vegetation period, the fungus spreads through spores (conidia); these are the inoculum for the repeating secondary cycle. It persists through its resistance mycelium, located under the bud scales, from one year to another. Black cleisthothecia (fungal structures in which the sexual ascospores are produced) may be found fully exposed on the mycelial patches. In autumn, they fall off leaves or drop to the ground with leaves and remain dormant during winter. The main source of infection in the spring is ascospores released from overwintering cleistothecia (Smith et al., 1988; Dickman et al., 1994; Anonymous, 2024).
[In responses to the questionnaire, NL commented that the pest was 'airborne and widespread in nature'.]
The Fruit SEWG considered that once present in an area, natural aerial spread is the main source of infection. Ribes plants for planting, generally propagated as cuttings, are not considered as a significant pathway.
5 - Economic impact:
Are there documented reports of any economic impact on the host?
No
Justification:
No specific reports on impact of European powdery mildew (Erysiphe grossulariae), since it is not as important as American powdery mildew (Podosphaera mors-uvae formerly known as Sphaerotheca mors-uvae). It is almost innocuous, causing little damage to bushes, but inducing some premature leaf fall (Smith et al., 1988). The Fruit SEWG highlighted that this has been solved by the development of resistant varieties (all recent varieties are resistant with no significant damage reported in such varieties).
[In responses to the questionnaire, SI considered that the pest was causing insignificant damage.]
[In responses to the questionnaire, SI considered that the pest was causing insignificant damage.]
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:
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:
Warm, humid conditions with poor air circulation favor powdery mildew.
To prevent the pathogen from appearing, it is recommended to place the planting material at a suitable distance to ensure good aeration. Apply pruning and keep the crop free of weeds (to enhance aeration).
In plantations affected by this fungus, it is recommended to prune and dispose of infected branch and shoot tips in early spring. Remove and burn the attacked leaves (Anonymous, 2019; Anonymous, 2024)
Take into account any attacks in previous years and carry out preventive fungicide treatment . Apply treatments during the dormant period with specific products. To control powdery mildew in vegetation, apply specific fungicides (Anonymous, 2024)
[In responses to the questionnaire, DE commented that 'a generally known pest that can be easily controlled by the operator should not be regulated as RNQP. Horizontal regulation in the marketing regulations should ensure that the consignments to be marketed/moved are “practically free from pests”'].
To prevent the pathogen from appearing, it is recommended to place the planting material at a suitable distance to ensure good aeration. Apply pruning and keep the crop free of weeds (to enhance aeration).
In plantations affected by this fungus, it is recommended to prune and dispose of infected branch and shoot tips in early spring. Remove and burn the attacked leaves (Anonymous, 2019; Anonymous, 2024)
Take into account any attacks in previous years and carry out preventive fungicide treatment . Apply treatments during the dormant period with specific products. To control powdery mildew in vegetation, apply specific fungicides (Anonymous, 2024)
[In responses to the questionnaire, DE commented that 'a generally known pest that can be easily controlled by the operator should not be regulated as RNQP. Horizontal regulation in the marketing regulations should ensure that the consignments to be marketed/moved are “practically free from pests”'].
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 as a significant pathway. No impact reported in recent varieties.
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:
- Anonymous (2019) Gooseberries and Currants, Ribes spp. (accessed 26/Aug/2024). http://www.hort.cornell.edu/fruit/mfruit/gooseberries.html
- Anonymous (2024) Gooseberry treatments, pest and disease control (accessed 26/Aug/2024) https://www.armuro.com/en/gooseberry-pest-disease-treatments/
- Bresinsky A (2016) Echte Mehltaupilze (Erysiphales) in Bayern: eine vorläufige Übersicht. Berichte der bayerischen botanischen Gesellschaft 86, 163-212.
- Diekmann M, Frison EA & Putter T (eds.) (1994) FAO/IPGRI technical guidelines for the safe movement of small fruit germplasm. Food and Agriculture Organization of the United Nations, Rome/International Plant Genetic Resources Institute, Rome.
- Ellis WN (2001-2024). Plant parasites of Europe: leafminers, galls and fungi. https://bladmineerders.nl/parasites/fungi/dikarya/ascomycota/pezizomycotina/leotiomycetes/leotiomycetidae/helotiales/erysiphaceae/erysiphe/erysiphe-grossulariae/ (accessed 16/Aug/2024).
- Horst RK (2001) Plant diseases and their pathogens (Chapter 3). In Wescott’s Plant Disease Handbook. Springer Science+Business Media New York. Pages 337-347
- Jage H, Klenke F & Kummer V (2010) Neufunde und bemerkenswerte Bestätigungen von phytoparasitischen Kleinpilzen in Deutschland: Erysiphales (Echte Mehltaupilze). Schlechtendalia, 21, 1-140.
- Kozłowska M, Mułenko W & Heluta VP (2015) Fungi of the Roztocze Region (Poland and Ukraine). 2. A checklist of microfungi and larger Ascomycota. pp 204.
- Mieslerová B, Sedlářová M, Michutová M, Petřeková V, Cook R & Lebeda A (2020) Powdery mildews on trees and shrubs in botanical gardens, parks and urban green areas in the Czech Republic. Forests 11(9), 967. https://doi.org/10.3390/f11090967..
- Smith IM, Dunez J, Lelliott RA, Phillips DH & Archer SA (eds) (1988) Microsphaera grossulariae (Wallr.) Lév & Sphaerotheca mors-uvae (Schwein.) Berk. & Curtis. In European Handbook of Plant Diseases. Blackwell Scientific Publications, Oxford, UK. Pages 262 & 266-267.