Abstract
Eucalyptus smithii is cold tolerant and thus ideal for commercial propagation in high altitude areas of South Africa. It grows fast and has superior pulping properties compared to other commercially grown eucalypts. Phytophthora dieback, however, limits the afforestation potential of this species. In this study, a survey was conducted in newly established E. smithii stands in the KwaZulu/Natai province of South Africa to identify and map the occurrence of Phytophthora spp. Soil and plant samples were collected from diseased trees and their Global Positioning System (GPS) coordinates recorded. Phytophthora spp. recovered from the soil and diseased plant material were identified using morphological characteristics and sequence data from the ITS region of the rDNA operon. Three Phytophthora spp., namely P. cinnamomi, P. citricola and P. nicotianae were recovered from soil and diseased plant material. Our results suggest that P. nicotianae is the most common species associated with E. smithii death. This is in contrast the previous view that P. cinnamoni is the dominant pathogen in this environment.