Chapter 4
I Management Of Native Forests
II Plantations-high Productivity Resources
III Protecting The Resource
i From fire
ii From biological attack
IV Harvesting The Resource
V Solid Wood And Its Processing
VI Minor Forest Products
VII Reconstituted Wood Products
VIII Pulp And Paper
IX Export Woodchips
X Future Directions
XI Acknowledgements
References
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From biological attack
Eucalypts are subject to attack by many organisms that share their natural environment -root-rot fungi, wood-rot fungi, termites, wood-boring insects, leaf rusts, leaf-eating insects, sap-sucking insects, mistletoes and browsing animals -and from time to time the destructive activity of one or more of these may increase to levels where concern may be felt for the productivity, or even the viability of the forest. In the 1920s crown die-back began to be noticed in the jarrah forests of Western Australia. Its incidence increased slowly at first but accelerated after the Second World War. In 1948 the WA Forests Department and the Forestry and Timber Bureau started a joint research program on the problem but it was not until 1964 that the cause was identified by Podger et al.[37] as the root-rot fungus Phytophthora cinnamomi. Its mode of spread was believed to be by movement of infected soil, during bauxite mining, road-making and forestry operations. Strict quarantine regulations were therefore introduced to prevent soil movement from affected areas, which were defined by large scale-aerial colour photography, and the disease now appears to have been effectively contained.Phytophthora has since also been found in some areas of Victoria, NSW and Queensland. Its occurrence amongst forest eucalypts seems to be mainly confined to the sub-genus Monocalyptus, particularly messmate and silvertop ash in south-eastern Australia and, as in Western Australia, some non-eucalypt understorey species are also susceptible. Research has been proceeding in a number of centres and Marks and Pegg[38] have recently reviewed this and set out principles upon which rehabilitation of affected areas can be based. Soil moisture and temperature appear to be important environmental factors and an increase in the former caused, for example, by poorly designed logging or roading practices is thought to encourage the disease.
Another root-rot fungus which has caused some concern in dry eucalypt forests in Victoria is Armillaria, which attacks trees from infected stumps. Where it is prevalent, removal and burning of infected stumps and roots has been used to control it. Its spread to other trees is less likely from clear-felled than selectively logged areas.[39]
A useful review of insects which attack the eucalypts in Australia has been given by Carne and Taylor.[40] As they point out, although many species are associated with the eucalypts, very few have become serious pests.
Eucalypt tree decline in rural areas -as opposed to forests - has been causing some concern in recent years but current opinion suggests that this is caused by a variety of factors rather than any widespread disease. Environmental stress, salinity, browsing by native animals and old age have all been invoked as well as pests and pathogens.[41]
Australia's non-eucalypt commercial timber species are also subject to attack by pests. The cedar tip moth proved to be a major obstacle to the establishment of red cedar plantations. In the 1940s a threat to Queensland's hoop pine plantations by the bark weevil (Aesiotes notabilis) was averted because a study undertaken by Brimblecombe[42] led to pruning being done only during dry periods in winter, when adult activity was reduced and larval establishment least favourable. This practice eliminated the problem both in hoop pine and exotic pine plantations to which it had also spread, although not to any serious extent.
Organisations in Australian Science at Work - Forestry and Timber Bureau; Western Australia. Forests Department
People in Bright Sparcs - Brimblecombe, A. R.; Carne, P. B.; Doepel, R. F.; Marks, G. C.; Pegg, K. G.; Podger, F. D.; Taylor, K. L.; Zentmyer, G. A.
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Australian Academy of Technological Sciences and Engineering |  |
© 1988 Print Edition pages 210 - 211, Online Edition 2000
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