Pectolytic enzyme activity of P. strasseri was highest in filtrates from cultures 5 and 23 days old, as determined by reducing-groups assay (RGA). Pectolytic enzyme activity, as determined by viscosity-reduction assay (VRA), was highest in cultures 7 days old. Macerating enzyme activities were highest in cultures 10 days old. Young peppermint-rhizome sections were more susceptible to maceration by P. strasseri filtrates than older sections. Colored phenolic compounds were released from macerated rhizomes and amounts released were correlated with degree of maceration.Differential inhibition of pectolytic enzyme activity (as judged by VRA and RGA assays) by a range of phenolic compounds suggests that at least two pectolytic enzymes capable of hydrolyzing α-1,4 linkages of pectic substances are produced by P. strasseri.Highest activities of pectolytic and macerating enzyme in extracts from diseased rhizomes were detected 5 days after inoculation with P. strasseri. Extracts from healthy rhizomes did not show pectolytic and macerating enzyme activity.Healthy peppermint-rhizome tissues had higher activities of polyphenoloxidase than diseased tissues; also, polyphenoloxidase activities in inoculated rhizomes decreased as time of incubation increased.