Taxonomic information	Current valid scientific name: Cryphonectria parasitica Synonyms: Diaporthe parasitica, Endothia gyrosa var. parasitica, Endothia parasitica, Valsonectria parasitica (according to Index Fungorum) Name used in the EU legislation: Cryphonectria parasitica (Murrill) Barr [ENDOPA] Order: Diaporthales Family: Cryphonectriaceae Common name: chestnut blight, blight of chestnut, canker of chestnut, blight of oak Name used in the Dossier: Cryphonectria parasitica
Group	Fungi
EPPO code	ENDOPA
Regulated status	The pathogen is listed in Annex III and in Annex VI of Commission Implementing Regulation (EU) 2019/2072 as Cryphonectria parasitica (Murrill) Barr. [ENDOPA]. It is EU protected zone quarantine pests of Czechia, Ireland, Sweden and the UK (Northern Ireland) and also RNQP (Regulated non‐quarantine pest) for plants for planting other than seeds of Castanea. Cryphonectria parasitica is a quarantine pest in Israel, Morocco, Norway and the US (EPPO, online_a). Cryphonectria parasitica is included in the EPPO A2 and in the A2 list of Jordan, Türkiye and COSAVE (Comite de Sanidad Vegetal del Cono Sur – Argentina, Brazil, Chile, Paraguay, Peru and Uruguay). It is also reported on A1 list of Argentina, Azerbaijan, Chile, the UK and IAPSC (Inter‐African Phytosanitary Council) (EPPO, online_a).
Pest status in the UK	Cryphonectria parasitica is present in the UK (CABI, online; Farr and Rossman, online). The pathogen was apparently eradicated after the first findings in 2011, then newly recorded in 2016; it was suggested that C. parasitica has been introduced to the UK multiple times over at least two decades through international plant trade (Perez‐Sierra et al., 2019). According to EPPO (online_b), the pathogen is present in the UK with restricted distribution. During surveys held in 2017–2018 and 2019–2020, Cryphonectria parasitica was detected in Berkshire, Buckinghamshire, Cornwall, Derbyshire, Devon, Dorset, London, West Sussex, Jersey and Guernsey (Perez‐Sierra et al., 2019; Romon‐Ochoa et al., 2022; EPPO, online_c; Forestry Commission, online). According to the Dossier Section 5.0, Cryphonectria parasitica is present, not widely distributed and under official control in Great Britain. It is present in central and southern England. In North Ireland, the pathogen is not recorded.
Pest status in the EU	Cryphonectria parasitica is present in the EU. It is widespread in Croatia, Italy and Portugal. It has restricted distribution in Austria, Belgium, Bulgaria, France, Germany, Greece, Hungary, Romania, Slovakia, Slovenia and Spain. The pathogen is present with few occurrences in Czechia and the Netherlands. In Poland, the pathogen was eradicated (EPPO online_b). Different areas in the EU have different strains of C. parasitica, the ability of new strains to spread in areas already infested by other strains seems to be very limited (EFSA PLH Panel, 2016).
Host status on Acer	Cryphonectria parasitica may infect Acer palmatum (Spaulding, 1961; Farr and Rossman, online) and Acer rubrum (Anderson and Babcock, 1913; Shear et al., 1917). There is no information on whether C. parasitica can also attack Acer pseudoplatanus. Acer spp. are reported as minor incidental hosts by Rigling and Prospero (2018).
PRA information	Available pest risk assessment: – Technical justification for Australia's requirement for wood packaging material to be bark free (Biosecurity Australia, 2006), – Rapid pest risk analysis for Cryphonectria parasitica (Anderson et al., 2013), – Scientific Opinion on the pest categorisation of Cryphonectria parasitica (Murrill) Barr (EFSA PLH Panel, 2014), – Scientific opinion on the risk assessment and reduction options for Cryphonectria parasitica in the EU (EFSA PLH Panel, 2016), – Scientific Opinion on the commodity risk assessment of Acer palmatum plants grafted on Acer davidii from China (EFSA PLH Panel, 2022), – UK Risk Register Details for Cryphonectria parasitica (DEFRA, online).
Other relevant information for the assessment
Biology	Cryphonectria parasitica is a pathogen in the family Cryphonectriaceae, native to East Asia (EPPO, online_b). It is present in Africa (Tunisia), Asia (China, India, Iran, Japan, North and South Korea, Taiwan), Europe, North America (Canada, the US) and Oceania (Australia) (EPPO, online_b). The biology section is based on the studies on chestnut, one of the major hosts. Cryphonectria parasitica is a bark pathogen that infects the tissue through wounds or growth cracks in the bark. The pathogen can also infect abandoned galls of the gall wasp Dryocosmus kuriphilus (Meyer et al., 2015). Hail wounds have been documented as important infection courts (Lione et al., 2020). The infection is caused by asexual and sexual spores. The infection develops in a lesion and a canker, which eventually kills the plant part distal to the infection. The pathogen can saprophytically colonise recently (1 year) dead stems or branches (Hepting, 1974; Prospero et al., 2006). Then stromata develop. Stromata can contain sexual fruiting bodies (perithecia), asexual ones (pycnidia) or both. Pycnidia produce conidia that are released in tendrils in moist condition and splash dispersed by rain in a few metres range. Conidia can also be dispersed by birds, insects and windborne dust over long distances (Wendt et al., 1983; Russin et al., 1984). Once in the ground conidia can survive for a long time (Heald and Studhalter, 1914). Perithecia produce ascospores that can be dispersed by wind over hundreds of metres and are relatively short‐lived. Ascospores are discharged from spring to autumn during warm rains (Heald and Gardner, 1914; Guérin et al., 2001). Sexual reproduction can be by both, outcrossing and self‐fertilisation (Marra et al., 2004). In northern Italy, it has been reported that C. parasitica can release propagules all over the year, though with significant seasonal peaks in the spring and fall. Large propagule loads were significantly correlated with an increasing number of rainy days of the week (days providing 1 ‐10 mm/day of water) (Lione et al., 2022). In newly established populations, asexual reproduction via conidia is often the predominant spreading mechanism (Rigling and Prospero, 2018). The canker growth can be as fast as 1 mm per day when the average daily temperature is 20°C, with a peak at 27°C and slowed down below 20°C (Bazzigher, 1981). The optimal germination temperature of conidia is 25–26°C, the ascospores' one is 21°C (Fulton, 1912). Humidity promotes spore release (Griffin, 1986), but drought stress can increase incidence and mortality of the pathogen (Roane et al., 1986; Waldboth and Oberhuber, 2009). The pathogen's ability to infect a new host is dependent on the age of the wound: on European chestnut C. parasitica cannot establish itself in wounds of four or more days (Bazzigher and Schmid, 1962). Cryphonectria parasitica can also show an endophytic behaviour, it has been found in symptomless stems 3 months after inoculation (Guérin and Robin, 2003) or developed its symptoms after 16 months of quarantine in Australia (Cunnington and Pascoe, 2003). On chestnut fruits, the fungus is associated with only the nutshell (Jaynes and Depalma, 1984).
	In newly colonised territories, the population usually consists of one or few genotypes, limiting sexual reproduction and long‐range dispersal via ascospores. In most populations in Europe, random mating has been ruled out and, even then, ascospores are not likely to be the primary inoculum (Milgroom and Cortesi, 1999). The main mycovirus acting as biological control agent for C. parasitica, reducing its virulence, in Europe is Cryphonectria hypovirus 1 (CHV‐1), one of the four known species of the genus Hypovirus (Turina and Rostagno, 2007). CHV‐1 can spread via hyphal anastomosis from one individual to another or via conidia, but not via ascospores. Fungi‐feeding mites can be important for the spread of CHV‐1 (Bouneb et al., 2016). Cryphonectria parasitica, like many fungi has a vegetative incompatibility (vic) mechanism. This mechanism usually hinders the transmission of mycoviruses including CHV1. Up to date, there are 64 genetically defined vic genotypes (Short et al., 2015). According to EFSA PLH Panel (2016), the main pathways of entry for C. parasitica are plants for planting (including seedlings, scions, rootstocks, ornamental plants), wood with bark (including chips, wood for tannin production, hoops for barrels), fruit (nuts), soil and growing media (including isolated chestnut bark), natural spread of airborne inoculum, biological agents able to mechanically transfer the fungus (e.g. birds, mammals, insects, mites, etc.) and machinery (construction, terracing, etc.) and pruning/cutting tools. According to EUROPHYT (online), Cryphonectria parasitica was intercepted 14 times on wood and bark of Castanea sp. or Castanea sativa. Once it was intercepted on Castanea sativa plants intended for planting: not yet planted. Cryphonectria parasitica is singlehandedly responsible for the removal from the forest dominant plane of Castanea dentata in North America. Impact of the pathogen is strongly dependent on host availability, host susceptibility and virulence of the Cryphonectria parasitica strain. An in‐depth analysis of the impact of introduction of new strains of the pathogen in EU countries where C. parasitica is already established and in countries where it is absent is available in the EFSA Pest Risk Assessment for Cryphonectria parasitica (EFSA PLH Panel, 2016).
Symptoms	Main type of symptoms	Cryphonectria parasitica only attacks the aboveground tree parts. Symptoms vary depending on the age of the host tree, its species, and the virulence of the particular pathogen strain (Heiniger and Rigling, 1994; Prospero and Rigling, 2013). Virulent strains on susceptible trees produce in few months cankers that can kill branches or twigs (Diller, 1965). On susceptible Castanea species, one of the first symptoms is branch wilting with wilted leaves hanging on the branches. Cankers typically appear as sunken, reddish‐brown bark lesions. Below the cankers, trees can produce epicormic shoots. At the canker border and under the bark, the fungus develops pale brown mycelial fans. On more resistant tree species (Asian chestnut species, oaks), cankers typically have a swollen appearance and are superficial or callused. There is no information on the symptoms caused by C. parasitica on Acer plants.
	Presence of asymptomatic plants	Cryphonectria parasitica can show an endophytic behaviour, imported chestnut plants have developed symptoms after 16 months of quarantine (Cunnington and Pascoe, 2003).
	Confusion with other pests	Cryphonectria parasitica symptoms can be confused with other cankers in the first stages, but the presence of mycelial fans and appearance of the fruiting bodies makes the identification clear. Isolated on potato dextrose agar can identify also hypovirus‐infected fungi, and molecular methods have been developed for identification (EFSA PLH Panel, 2014). Some confusion can occur with cancers caused by Gnomonopsis castaneae (Lione et al., 2019).
Host plant range	Main host of Cryphonectria parasitica are Castanea dentata and C. sativa. Other hosts in the Castanea genus are C. crenata, C. henryi, C. mollissima, C. ozarkensis, C. pumila and C. seguinii. Among oaks the known hosts are Quercus alba, Q. coccinea, Q. frainetto, Q. ilex, Q. montana, Q. petraea, Q. prinus, Q. pubescens, Q. stellata, Q. suber, Q. velutina and Q. virginiana. Cryphonectria parasitica was also reported on Aesculus hippocastanum, Carya ovata, Carpinus betulus, Eucalyptus camaldulensis, E. haemastoma, E. microcorys, E. punctata, E. robusta, Rhus typhina and Fagus sylvatica (EPPO, online_d; Farr and Rossman, online). The reports for Fagus sylvatica are only taken from artificial inoculation (Dennert et al., 2020). Acer palmatum is a known host for C. parasitica (EPPO, online_d; Farr and Rossman, online). Cryphonectria parasitica has also been reported on Acer rubrum in North America (Anderson and Babcock, 1913; Shear et al., 1917). Inoculation experiments indicated that bark of Acer rubrum is much less susceptible than the bark of Quercus sp. (Baird, 1991).
Reported evidence of impact	Cryphonectria parasitica is EU protected zone quarantine pest.
Evidence that the commodity is a pathway	Host plants for planting, excluding seeds, but including dormant plants, have been identified as pathways by EFSA PLH Panel (2014), and have been historically pathways even after quarantine (Cunnington and Pascoe, 2003).
Surveillance information	Cryphonectria parasitica is a regulated quarantine pest for Great Britain subject to eradication measures, unless in the wider environment where a containment policy may be taken dependent on the site. As part of an annual survey at ornamental retail and production sites (frequency of visits determined by a decision matrix), Cryphonectria parasitica is inspected for on common hosts plants (Dossier Section 3.0 and 5.0).