Changes in the Distribution of Phytophthora cinnamomi in the Brisbane Ranges National Park Between 1970 and 1980-81

Abstract

The distribution of Phytophthora cinnamomi in the Brisbane Ranges National Park of Victoria was mapped and related to vegetation susceptibility, disease severity and past distribution. P. cinnamomi extended its distribution from 1% of the park in 1970 to 31% in 1980-81. The dispersal of the pathogen has occurred through roadworks and subsequent drainage of water-borne zoospores. In 1980-81, 50% of 1191 grids (250 x 250 m) occurred in susceptible vegetation (sclerophyllous forest/woodland). Of these, 45% (266 grids) were moderately diseased and 16% (95) severely diseased. Stands of dead trees occurred in 29 severely diseased grids which were in shallow gullies with impeded drainage. The 39% (231) of susceptible vegetation which remained unaffected occurred mainly on ridges and hilltops. P. cinnamomi was isolated from 3% of apparently resistant vegetation (graminoid forest/woodland). Restriction of access is recommended to the remaining areas of susceptible unaffected vegetation.