AbstractPectinasc activities of Nectria ditissima Tul. cause of the Beech canker.In vitro, Nectria ditissimais capable of secreting pectinases necessary for degradation of pectic material of the cell wall. Some pectinascs, ENDOPG, EXOPG and EXOPMG, play a prominent part in degradation of the barkin vivo, their primary participation being affected by the conditions of the bark environment, especially pH. The virulence of four pathogenically different strains ofN. ditissimais partly correlated with their ability to produce the pectinace essential for alteration of the barkin vitro.