Contrasting the infection and survival of Phytophthora pluvialis and Phytophthora cinnamomi in Pinus radiata roots

Phytophthora pluvialis has been shown to be a foliar pathogen of various species of Pinaceae in North America and New Zealand where it has been primarily associated with red needle cast on Pinus radiata and Pseudotsuga menziesii but has also been isolated from Pinus patula and Pinus strobus. To better manage the disease and potential biosecurity implications of germplasm movement, there is much to learn about the epidemiology of the pathogen including where and how it infects hosts, affects productivity and survives during periods that are unfavourable for needle disease. While P. pluvialis is yet to be associated with root disease, most aerially dispersed Phytophthora species are known to infect and survive in roots. This study investigates the potential for P. pluvialis to infect and survive within the root system of P. radiata and its impact on the fine roots of plants up to six weeks post inoculation. Results were comparable to symptoms developed in fine roots infected by P. cinnamomi and demonstrate the potential for P. pluvialis to infect and affect the growth of P. radiata at what are likely to be sub-lethal levels .