A SUPPRESSION ASSAY FOR ASSESSING THE EFFECT OF MANAGEMENT PRACTICES ON PACHYMETRA ROOT ROT

THE paper describes glasshouse methods used to investigate the presence of suppression to Pachymetra root rot in field soils. The technique involves growing a susceptible variety in unamended field soil, and in soil with two or more levels of added Pachymetra inoculum. The relationship between percentage of rotted roots and inoculum density in each treatment is compared to determine if factors other than inoculum density are influencing root rot severity. This technique offers promise for use with soils subjected to a range of management practices. A complicating factor is the presence of naturally-occurring Pachymetra inoculum in untreated soils. Suppression was detected in soils from several sites under different cropping regimes. Pasture, bare fallow and even continuous cane rotation soils showed evidence of suppression to Pachymetra root rot, seen as higher levels of root rot in inoculated, fumigated soils.