Two further threats to Ireland’s trees from non-native invasive Phytophthoras.

Abstract

The genus Phytophthora contains many plant pathogens, including the causal agents of sudden larch death (Phytophthora ramorum) and of the late potato blight (P. infestans). Phytophthora species are estimated to be one of the most threatening biotic agents to forest health worldwide. The species P. austrocedri and P. pinifolia are currently causing disease epidemics in forests in Argentina and Chile, respectively. Although neither species has yet been recorded in Ireland, P. austrocedri has recently been found in Britain. The threat that P. austrocedri and P. pinifolia pose to Irish forests is briefly reviewed in this paper. The threat level posed by these species is ranked in relation to the risk of (i) entry into Ireland and (ii) likely establishment of species in the wild in Ireland. P. austrocedri is of medium threat to Irish forests, given that it is currently present in Britain and has been found in 2001 in Germany on an imported ornamental juniper plant. Furthermore, known hosts of P. austrocedri are distributed across the Irish landscape. P. pinifolia was ranked as being a low level threat to Ireland’s forests. This ranking is a result of the lack of any obvious entry pathway for the pathogen into Ireland and the low frequency of suitable hosts for the organism in Ireland. A large degree of uncertainty in the biology of these organisms was evident from this analysis. Once a pathogen becomes established in the wild, it can be very difficult to eradicate. Being situated at the edge of Europe, Ireland is in a good position to monitor current forest epidemics in mainland European forests and to act to prevent similar outbreaks in Irish forests.