Assessing the potential for biological control of Phytophthora cinnamomi by fifteen native Western Australian jarrah-forest legume species

Fifteen native Western Australian legumes were assessed for their potential to biologically control Phytophthora cinnamomi. Biological control was assessed in a controlled situation, conducive to P. cinnamomi, and was based on susceptibility to the pathogen, ability to reduce soil inoculum, amount of asymptomatic root infection and ability for P. cinnamomi to effectively sporulate from asymptomatically infected roots. Acacia extensa, Acacia stenoptera and Acacia alata along with Acacia pulchella, were identified as species with the highest potential for biological control of P. cinnamomi. Acacia urophylla and Viminaria juncea exhibited the least potential for biological control; these are more likely to harbour the pathogen and provide a source of inoculum when conditions become conducive for P. cinnamomi growth and development. These findings have important implications for managing the rehabilitation of bauxite-mined P. cinnamomi-infested areas and severely disease-affected forest. By manipulating rehabilitation seed mix ratios, the density of legume species that suppress P. cinnamomi inoculum in the soil can be increased and the density of those that harbour the pathogen can be reduced. This could potentially contain the activity of P. cinnamomi soil inoculum in infested areas to protect susceptible species and enhance species diversity. Further research is required to ascertain the action of suppression before implementing control measures.