AbstractCrude aqueous extracts from the peripheral rot zone of cocoyam tubers infected bySclerotium rolfsii saccwere shown to be inhibitory to dialysed in vivo polygalacturonase (PG) of the pathogen. The PG inhibitory action, phenol oxidase and peroxidase activities were higher in cocoyam tubers of theXanthosoma sagittifoliumvarieties than in those of theCoolocasia esculentavarieties. The levels of phenol oxidase, peroxidase and PG inhibitory activities also decreased as the postharvest age of the tubers increased.