Evaluation continues

Candidate

C. parasitica can spread via the movement of infected host plants for planting (rootstocks, scions, grafted plants, self-rooted plants, etc.), particularly asymptomatic. Pruning and grafting tools or other equipment used in chestnut nurseries, orchards or forests may potentially spread the disease locally. C. parasitica propagules (ascospores and conidia) can spread locally by wind and/or rain, but might also occasionally be carried by other agents, such as arthropods and birds. However animal vectors are not considered to play a very important role in disease transmission. Many factors may influence the relative importance of ascospores versus conidia and mycelia as the primary inoculum for initiating new cankers or for disease epidemics. Experts considered that infection of seedlings are possible even if it has not been demonstrated so far (EFSA, 2014). Because uncertainty exists about the role of ascospores in disease epidemiology, on natural spread by arthropods and birds, and about the distribution of minor hosts, plants for planting are considered to be a significant pathway for the pest/host/intended use combination. Experts expressed a specific concern about pathway for locally aggressive strains, which would at the same time reduce effectiveness of hypovirulence as control.

Yes

C. parasitica causes cankers, wilt and diebacks, resulting sometimes in the death of its hosts (when on Castanea). Disease incidence ranges from less than 1% in the recently infested areas (such as Germany) to more than 90% in the countries where the pathogen has existed for a long time (e.g. Italy, France, Switzerland, Portugal, etc.). However, there is no direct relationship between disease incidence and impact (EU COM, 2015).

Medium

No

Candidate

There are several assessments of the potential economic impact depending on the European region considered. The presence of natural hypovirulent strains or more tolerant species must also be taken into account, which means that a uniform response cannot be categorically established at European level (Braganca et al., 2007; Tizado et al., 2012; Bryner et al., 2012). This is why the economic impact is proposed as medium. The presence of the pathogen into the host plant is not acceptable due to its transmission character and to the damage that causes (Anderson et al., 2013).

candidate

Avoiding human induced introduction of new strains and identifying and promoting local hipovirulence strains have showed an effective method of managing chestnut plantations (Robin et al., 2010; Anderson et al., 2013; Petto et al., 2013).