The Invasion of Native Forest by Phytophthora cinnamomi. III. Threat to the National Park, Wilson's Promontory, Victoria

Abstract

Diseased vegetation was first reported from the northern slopes of the Vereker Range at Wilson's Promontory National Park in September 1970. Phytophthora cinnamomi was isolated from plants in diseased areas but not from unaffected localities. The pathogen has since invaded three types of plant community-dry sclerophyll woodland, heaths, and swamps-and can be isolated at all depths to 80 cm in deep sands. High inoculum potentials are found at depths of maximum root concentration, i.e, to about 32 cm. Except where free water occurs, the rate of extension of the disease is slow. Dominants of both tree and shrub strata are susceptible and have been killed. Highly susceptible shrubs of the understorey, such as Xanthorrhoea australis and Isopogon ceratophyllus, are destroyed first. These are followed 6-12 months later by less susceptible shrubs, and at least 12 months later symptoms appear in trees. This variation in time may be responsible for the characteristic mosaic appearance of diseased areas. Inoculation experiments on 9-month-old trees of Banksia serrata and Eucalyptus obliqua confirmed field observations of susceptibility and symptom expression. The origin of the disease at Wilson's Promontory and its ecological significance are examined. Experiments in control of the pathogen are reported and recommendations discussed for control within the National Park.