Die-back in the mixed hardwood forests of eastern Victoria: A preliminary report

Abstract

The distribution and symptoms of die-back in the mixed-species eucalypt hardwood forests of eastern Victoria are described. The disease was recognizedin 1952 in small patches of forest situated in the flat, badly drained sandy coastal soils and has spread rapidly. This spread was associated with above-average rainfall during spring, summer, and autumn. Disease symptoms were similar to that caused by drought, and were observed best during dry periods following summer rain. The lupin bait of Chee and Newhook was used to isolate Phytophthora cinna- momi from the diseased areas, and the field symptoms seen on susceptible eucalypts of the subgenus Renantherae were similar to those observed on young saplings inoculated with P. cinnamomi in the greenhouse. Species of the subgenus Macrantherae observed in the forests and tested in the greenhouse are tolerant to the disease. Estimates of population density indices of the fungus gave highest values in areas where the disease was most active. The fungus was not isolated from adjacent healthy forests. Improvements in the baiting and identification of P. cinnamomi with use of excised lupin radicles floated over a small sample of soil in a petri dish are described. Several variants of the fungus with differing growth rates were isolated.

Tree Decline and Mortality in Selectively Logged Eucalypt Forests in Central Victoria

“…P. cinnamomi, a known cause of eucalypt dieback (Podger et al 1965, Marks et al 1972, has been detected in parts of the Wombat State Forest where it causes dieback on sites with shallow, poorly drained soils derived from Ordovician sediments. Severe dieback is also present in many areas of that forest where the fungus is apparently absent, and in spite of attempts to do so the fungus has not been isolated from soils in the Mount Cole and Macedon forests.…”

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.…”

Response of selected South Australian native plant species to Phytophthora cinnamomi

“…In Australia, the disease also causes damage of epidemic proportions to native vegetation in many regions, particularly in the south‐eastern and south‐western regions of the country. The disease was first associated with the death of a large number of native plants in the jarrah forests in Western Australia in 1921 (Podger, 1972) and in 1952 in Gippsland in the south‐east of Victoria (Marks et al. , 1972).…”

“…In Australia, the disease also causes damage of epidemic proportions to native vegetation in many regions, particularly in the south-eastern and south-western regions of the country. The disease was first associated with the death of a large number of native plants in the jarrah forests in Western Australia in 1921 (Podger, 1972) and in 1952 in Gippsland in the south-east of Victoria (Marks et al, 1972). By the 1990s, the disease had destroyed large areas of native vegetation in Western Australia, Tasmania, Queensland and Victoria, causing local susceptible species to disappear (Weste, 1986).…”