| Legend |
|---|
| Justification for qualification based on EPPO PM 4 Standards |
| Justification for disqualification |
| Additional or non-conclusive information |
| Standard text |
NAME OF THE ORGANISM: Badnavirus tessellocastaneae (chestnut mosaic virus) {Chestnut mosaic agent} (CHNMV0)
GENERAL INFORMATION ON THE PEST
Name as submitted in the project specification (if different):
Chestnut mosaic
Pest category:
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?
?
Is the pest defined at the species level or lower?:
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?
- Null: 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):
For more than sixty years, the possible causes of chestnut mosaic disease remained unknown. Since the 1980s, this disease has been observed in chestnut commercial orchards in France and Italy. There were also records from Hungary and Japan. Past studies had shown that this disease was graft-transmissible, eliminated by thermotherapy and transmitted by aphids. Recent studies (HTS, phylogenetic analyses) have demonstrated that a new badnavirus, tentatively called Chestnut mosaic virus (ChMV) is associated with this disease. Although Koch’s postulates were not fully verified, experiments strongly suggest that ChMV is the causal agent of chestnut mosaic disease. The low diversity of ChMV isolates from France and Italy also indicates that this virus is of recent introduction in Europe (Marais et al., 2021).
EPPO GD lists 'yellow mosaic of horse chestnut’ as a synonym of Apple mosaic virus (ApMV). CABI datasheets also list ‘Chestnut mosaic’ as a synonym of ApMV. On EPPO GD, Castanea sativa (sweet chestnut) is not listed as a host of Apple mosaic virus, but Aesculus hippocastanum (horse chestnut) is listed as a major host. All data suggest that chestnut mosaic virus is not apple mosaic virus. No literature found linking chestnut mosaic and apple mosaic virus. Only papers about chestnut mosaic as an unidentified agent.
‘Chestnut mosaic’ on sweet chestnut (C. sativa) was detected through glasshouse indexing of sensitive Castanea hybrids (Desvignes, 1992). Graft-inoculation to Corylus avellana (host of apple mosaic virus) evoked symptoms (dwarfing) but back-inoculation to chestnut was unsuccessful (Desvignes & Lecocq, 1995). The authors concluded that C. avellana probably is not a host of chestnut mosaic virus. In addition, graft-inoculation to Quercus pedunculata and Quercus rubra (both not known as hosts of apple mosaic virus) was successful (Desvignes & Lecocq, 1995; Desvignes, 1999). Moreover, Desvignes (1999) reported transmission of chestnut mosaic virus by the aphid Myzocallis castanicola, whereas apple mosaic virus is not known to be transmitted in this way.
In conclusion, chestnut mosaic agent (on Castanea sativa) would be the most appropriate name, chestnut mosaic virus being (one of the)(the) causal agent(s). Considering Marais et al, 2021 (see below), the Fruit SEWG considered that chestnut mosaic virus could remain listed in the regulation. Assessment of the RNQP status continues solely on this virus.
Remark: In responses to the questionnaire, only DE and FR supported the recommendation of the agent as an RNQP, whereas NL suggested the individual listing of chestnut mosaic virus.
Evidence that ChMV could be the cause of chestnut mosaic disease:
1) ChMV was the sole virus detected in a French source from a ChMD source initially involving a C. sativa x C. crenata hybrid.
2) ChMV was also the sole virus detected in the Italian ChMD source
3) ChMV was consistently detected in other symptomatic accessions derived from the same diseased source (in Quercus ruba – artificially inoculated, in an indicator plant inoculated by aphid transmission).
4) Three other independent chestnut sources, shown by biological indexing on ‘Maraval’ indicator to be infected with ChMD, were found to be infected by ChMV.
Therefore, there is a correlation between the appearance of ChMVd symptoms and the presence of ChMV in graft-inoculated indicators, supporting the hypothesis of a causal relationship between ChMV infection and ChMD (Marais et al., 2021).
In surveys ChMV was not systematically associated with symptomatic infections, although its frequency was systematically higher in symptomatic plants. This was to be expected because previous grafting experiments had demonstrated that not all chestnut varieties/species are susceptible to ChMD and develop symptomatic infections. However, all surveyed symptomatic plants in France were found to harbor the virus, whereas it was detected in 87% tested symptomatic Italian trees. The latter might be a result of an uneven distribution of ChMVd agent in infected trees, which was also reported before (Marais et al., 2021).
EPPO GD lists 'yellow mosaic of horse chestnut’ as a synonym of Apple mosaic virus (ApMV). CABI datasheets also list ‘Chestnut mosaic’ as a synonym of ApMV. On EPPO GD, Castanea sativa (sweet chestnut) is not listed as a host of Apple mosaic virus, but Aesculus hippocastanum (horse chestnut) is listed as a major host. All data suggest that chestnut mosaic virus is not apple mosaic virus. No literature found linking chestnut mosaic and apple mosaic virus. Only papers about chestnut mosaic as an unidentified agent.
‘Chestnut mosaic’ on sweet chestnut (C. sativa) was detected through glasshouse indexing of sensitive Castanea hybrids (Desvignes, 1992). Graft-inoculation to Corylus avellana (host of apple mosaic virus) evoked symptoms (dwarfing) but back-inoculation to chestnut was unsuccessful (Desvignes & Lecocq, 1995). The authors concluded that C. avellana probably is not a host of chestnut mosaic virus. In addition, graft-inoculation to Quercus pedunculata and Quercus rubra (both not known as hosts of apple mosaic virus) was successful (Desvignes & Lecocq, 1995; Desvignes, 1999). Moreover, Desvignes (1999) reported transmission of chestnut mosaic virus by the aphid Myzocallis castanicola, whereas apple mosaic virus is not known to be transmitted in this way.
In conclusion, chestnut mosaic agent (on Castanea sativa) would be the most appropriate name, chestnut mosaic virus being (one of the)(the) causal agent(s). Considering Marais et al, 2021 (see below), the Fruit SEWG considered that chestnut mosaic virus could remain listed in the regulation. Assessment of the RNQP status continues solely on this virus.
Remark: In responses to the questionnaire, only DE and FR supported the recommendation of the agent as an RNQP, whereas NL suggested the individual listing of chestnut mosaic virus.
Evidence that ChMV could be the cause of chestnut mosaic disease:
1) ChMV was the sole virus detected in a French source from a ChMD source initially involving a C. sativa x C. crenata hybrid.
2) ChMV was also the sole virus detected in the Italian ChMD source
3) ChMV was consistently detected in other symptomatic accessions derived from the same diseased source (in Quercus ruba – artificially inoculated, in an indicator plant inoculated by aphid transmission).
4) Three other independent chestnut sources, shown by biological indexing on ‘Maraval’ indicator to be infected with ChMD, were found to be infected by ChMV.
Therefore, there is a correlation between the appearance of ChMVd symptoms and the presence of ChMV in graft-inoculated indicators, supporting the hypothesis of a causal relationship between ChMV infection and ChMD (Marais et al., 2021).
In surveys ChMV was not systematically associated with symptomatic infections, although its frequency was systematically higher in symptomatic plants. This was to be expected because previous grafting experiments had demonstrated that not all chestnut varieties/species are susceptible to ChMD and develop symptomatic infections. However, all surveyed symptomatic plants in France were found to harbor the virus, whereas it was detected in 87% tested symptomatic Italian trees. The latter might be a result of an uneven distribution of ChMVd agent in infected trees, which was also reported before (Marais et al., 2021).
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):
see taxonomy.
HOST PLANT N°1: Castanea sativa (CSNSA) 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:
The virus, Chestnut mosaic virus (ChMV, Badnavirus tessellocastaneae), is linked to chestnut mosaic disease. As far as known, it has a narrow host range: Castanea spp. (C. sativa, C. crenata, C. mollissima, C. dentata) and Quercus spp. (Marais et al., 2021). However, not all Castanea spp. and varieties will show symptoms (Desvignes, 1992; 1999; Desvignes & Lecocq, 1995).
It is hypothesized that ChMD could be introduced in Europe between 1940 and 1960, when a number of Castanea crenata cultivars were imported from Japan for breeding purposes. The low diversity of ChMV isolates from France and Italy also indicates that this virus is of recent introduction in Europe (Marais et al., 2021). This means that the virus can be dispersed with plant material.
The virus is transmitted by grafting (Murolo et al., 2023).
The virus can be transmitted by the aphid Myzocallis castanicola (Marais et al., 2021).
The Fruit SEWG considered that plants for planting should be considered as a significant pathway.
It is hypothesized that ChMD could be introduced in Europe between 1940 and 1960, when a number of Castanea crenata cultivars were imported from Japan for breeding purposes. The low diversity of ChMV isolates from France and Italy also indicates that this virus is of recent introduction in Europe (Marais et al., 2021). This means that the virus can be dispersed with plant material.
The virus is transmitted by grafting (Murolo et al., 2023).
The virus can be transmitted by the aphid Myzocallis castanicola (Marais et al., 2021).
The Fruit SEWG considered that plants for planting should be considered as a significant pathway.
5 - Economic impact:
Are there documented reports of any economic impact on the host?
Yes
Justification:
On susceptible chestnut cultivars, initial symptoms are light and dark green patches on the leaves, accompanied by shoots with asymmetric blade deformation and then the severity of symptoms increases, starting with leaf curling, light mosaic, and finally with desiccation of the leaf lamina (Murolo et al., 2023). In bark and wood it also induces necrotic lesions which turn into cankers, or incompatibilities when two cultivars of different sensitivity are assembled through grafting (Desvignes, 1999). Some chestnut hybrids (i.e., ‘Maraval’) are particularly sensitive (Murolo et al., 2023).
At present, the majority of traditional varieties used in the main production area of Spain seem to be asymptomatic (C. Martinez, MAPA (ES), pers. comm., 2025); and the described symptoms (ChMD and yellowing caused by manganese deficiency) seem to be a limited problem for Italian orchards and chestnut woods. However, the increase in new reports suggests that these symptoms need to be considered as an emerging issue whose impact is still to be studied and understood. The exception is the Marche region (central eastern Italy) where in chestnut orchards both young and mature plants were affected, thus significantly decreasing chestnut production (Marais et al., 2021). Most plants infected with badnaviruses are generally symptomless, but abiotic stress (such as temperature shifts and depletion of nutrients) can break the latency of the virus, with reemergence and an increase of severity of symptoms. In the context of climate change, virulence could increase, with the risk of severe outbreaks (Murolo et al., 2023).
At present, the majority of traditional varieties used in the main production area of Spain seem to be asymptomatic (C. Martinez, MAPA (ES), pers. comm., 2025); and the described symptoms (ChMD and yellowing caused by manganese deficiency) seem to be a limited problem for Italian orchards and chestnut woods. However, the increase in new reports suggests that these symptoms need to be considered as an emerging issue whose impact is still to be studied and understood. The exception is the Marche region (central eastern Italy) where in chestnut orchards both young and mature plants were affected, thus significantly decreasing chestnut production (Marais et al., 2021). Most plants infected with badnaviruses are generally symptomless, but abiotic stress (such as temperature shifts and depletion of nutrients) can break the latency of the virus, with reemergence and an increase of severity of symptoms. In the context of climate change, virulence could increase, with the risk of severe outbreaks (Murolo et al., 2023).
What is the likely economic impact of the pest irrespective of its infestation source in the absence of phytosanitary measures? (= official measures)
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?
No
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:
Candidate
Justification:
Although not being as severe as Cryphonectria parasitica and Phytophthora cinnamomi, the pests causing chestnut blight and ink disease, leaf spot (Marssonina ochroleuca), twig canker (Cryptodiaporthe castanea), and chestnut mosaic virus (ChMV) are also reported to affect chestnut (Fernandes et al., 2022; citing Serdar et al., 2019).
The Fruit SEWG considered that data on economic impact was still lacking.
The Fruit SEWG considered that data on economic impact was still lacking.
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:
Testing for ChMV.
Healthy propagation material.
Most plants infected with badnaviruses are generally symptomless, but abiotic stress (such as temperature shifts and depletion of nutrients) can break the latency of the virus, with reemergence and an increase of severity of symptoms. This situation, which can depend on the viral variants and chestnut genotypes, opens questions on the role of asymptomatic plants in the epidemiology of the virus, and the importance of selecting “ChMV-free” plants from which to collect propagating materials (scions, buds) for grafting in nurseries and orchards. In the context of climate change, both viral spread and virulence could increase, with the risk of severe outbreaks (Murolo et al., 2024).
Healthy propagation material.
Most plants infected with badnaviruses are generally symptomless, but abiotic stress (such as temperature shifts and depletion of nutrients) can break the latency of the virus, with reemergence and an increase of severity of symptoms. This situation, which can depend on the viral variants and chestnut genotypes, opens questions on the role of asymptomatic plants in the epidemiology of the virus, and the importance of selecting “ChMV-free” plants from which to collect propagating materials (scions, buds) for grafting in nurseries and orchards. In the context of climate change, both viral spread and virulence could increase, with the risk of severe outbreaks (Murolo et al., 2024).
7- Is the quality of the data sufficient to recommend the pest to be listed as a RNQP?
No
Conclusion:
Candidate by default
Justification:
Data on economic impact is lacking.
CONCLUSION ON THE STATUS:
Recommended for listing as an RNQP, by default (lack of data on economic impact). 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:
- Desvignes (1992) Characterisation of the chestnut mosaic virus. Acta Horticulturae 309, 353-358.
- Desvignes & Lecocq (1995) New knowledge on the chestnut mosaic virus disease. Acta Horiculturae 386, 578-584.
- Desvignes (1999) Sweet chestnut incompatibility and mosaics caused by the chestnut mosaic virus (ChMV). Acta Horticulturae 494, 451-458.
- Fernandes P, Colavolpe MB, Serrazina S & Costa RL (2022) European and American chestnuts: An overview of the main threats and control efforts. Frontiers in Plant Science 13, 951844.
- Marais A, Murolo S, Faure C, Brans Y, Larue C, Maclot F, Massart S, Chiumenti M, Minafra A, Romanazzi G, Lefebvre M, Barreneche T, Robin C, Petit RJ & Candresse T (2021) Sixty years from the first disease description, a novel badnavirus associated with chestnut mosaic disease. Phytopathology 111(6), 1051-1058.
- Murolo S, Bertoldi D, Pedrazzoli F, Mancini M, Romanazzi G & Maresi G (2022) New symptoms in Castanea sativa stands in Italy: chestnut mosaic virus and nutrient deficiency. Forests 13(11), 1894.
- Murolo S, Marais A, Brans Y, Faure C, Gamba G, Marinoni Torello D, Tura E, Latour F, Carloni F, Minafra A, Cardone M, Beccaro GL & Romanazzi G (2024). Chestnut mosaic virus: grafting-transmissibility and the interference with plant canopy. Acta Horticulturae 1400, 117-124.