Phytophthora cinnamomi as a driver of forest change: Implications for conservation and management

Phytophthora cinnamomi is a soil-borne plant pathogen of global significance, threatening many forest tree species around the world. In contrast to other well-known tree pathogens, P. cinnamomi is a generalist pathogen that, in many cases, causes less immediately obvious symptoms, making P. cinnamomi more difficult to diagnose. This creates special challenges for those trying to assess and manage diseases caused by P. cinnanmomi. P. cinnamomi affects a wide range of tree species across the world including chestnuts, particularly American and European chestnuts, Eucalyptus and Banksia species in Australia, and oaks in Mediterranean Europe. We believe that forest professionals should incorporate an understanding of the diseases caused by P. cinnamomi in conservation, management, and restoration of threatened ecosystems dominated by P. cinnamomi-affected tree species. Here we review the impact of P. cinnamomi on forest ecosystems internationally and suggest three major strategies for improving forest resilience to P. cinnamomi: (1) Improving site quality to reduce risk of P. cinnamomi-related disease, (2) Genetically improving threatened species to improve resistance to P. cinnamomi, and (3) Restricting further spread (especially by nursery trade) of P. cinnamomi.