The Origin and Distribution of Phytophthora Cinnamomi Rands in Australian Native Plant Communities and the Significance of Its Association With Particular Plant Species

Abstract

The origin, distribution, and disease association of P. cinnamomi in native plant communities in Australia has been examined.

Eucalypt decline in Australia, and a general concept of tree decline and dieback

“…Waterlogging, 'Phytophthora dieback' and other declines and diebacks are associated with water gaining sites on shallow soils with impeded drainage (e.g. Pratt and Heather, 1973;Ward and McKimm, 1982;Manion, 1991;Shearer and Smith, 2000;Weste, 2003). This suggests that dysfunction of tree roots is the general cause of decline.…”

“…The fungus is common and widespread on both sides of the border (Pratt and Heather, 1973;Marks et al, 1975;Gerrettson-Cornell et al, 1979;Bridges et al, 1980) but intensive logging and climatic extremes did not incite epidemics in New South Wales (e.g. Hopkins, 1974;Bridges et al, 1980).…”

“…Dieback has been associated with very wet and/or dry seasons on poorly drained sites affected by human management such as tree cutting, earthworks and severe fires (Marks et al, 1975;Fagg et al, 1986;Davison, 1997;Shearer and Smith, 2000). Whether or not Phytophthora is exotic in parts of its range (Pratt and Heather, 1973), root disease is associated with human disturbance. It first became apparent after heavy machinery and intensive logging operations were introduced into forests on subdued topography with poorly drained soils (Marks et al, 1975;Shearer and Smith, 2000).…”

How Phytophthora cinnamomi became associated with the death of Eucalyptus marginata – the early investigations into jarrah dieback

“…There was a failure by plant pathologists to recognise the limitations of the methods used, and to ask questions about sample sizes and isolation frequencies. During the 1970s his soil baiting method was widely used in eastern Australia to raise concern that the presence of P. cinnamomi would lead to tree decline and dieback (Weste and Taylor 1971;Marks et al 1972;Pratt and Heather 1973). Even the observations that there did not appear to be extensive fine root necrosis of jarrah in forest trees (Shea et al 1980;Shea and Dell 1981) did not raise questions about how jarrah was infected and how the trees died.…”

“…The reason for these deaths had not been determined, in spite of many investigations into possible causes (Harding 1949;Wallace and Hatch 1953;Stahl and Greaves 1959). Within a few years of Podger's discovery, P. cinnamomi was associated with tree declines and dieback in other areas of Australasia (Weste and Taylor 1971;Marks et al 1972;Newhook and Podger 1972;Pratt and Heather 1973) and around the world (e.g., Kliejunas and Ko 1975;Lübbe and Mostert 1991;Brasier et al 1993;Tainter et al 2000;Balci and Halmschlager 2003). What was not realised was that Podger's data did not support his conclusion about the role of P. cinnamomi in the death of jarrah trees (Davison 2014), although they supported its role in the death of many smaller woody plants.…”