Survival of Phytophthora cinnamomi in plant material under different soil and moisture conditions

Soil moisture and the type of organic matter colonised by Phylophlhora cinnamomi significantly affected long-term survival of the pathogen. Banksia grandis stem pieces, and root tips of Eucalyptus marginata (jarrah) colonised with P. cinnamomi were placed into pots filled with soil from the jarrah forest or an adjacent rehabilitated bauxite mine site in the south west of Western Australia. The soil was either maintained at container capacity, or allowed to dry-out slowly from container capacity. Samples were harvested over a 210-day period and assessed for P. cinnamomi survival. P. cinnamomi was recovered after 210 days from banksia stems (98% colonisation) and eucalypt root tips (45% colonisation) from both soil types when the soil was maintained at container capacity. However when the soils were allowed to dry, the pathogen was not recovered after 112 days from either banksia stems or eucalypt roots. Soil origin did not influence P. cinnamomi survival for either inoculum type. These findings indicate that under moist conditions the pathogen can survive in small pieces of organic matter for extended periods of time.