Management of fungal root rot in plantation acacias in Indonesia

Pathogen biology and dispersal: The primary fungal species associated with red root-rot is Ganoderma philippii as determined by DNA analysis of isolates from diseased roots and from the association of fruiting bodies of this species with expanding patches of dead trees in Indonesian plantations.
Monitoring the manner of spread of the fungus has begun with the establishment of 15 semi-permanent survey plots at 4 sites and collection of fungal fruiting bodies from more than 16 additional sites. The first 6-monthly survey plot monitoring has also been completed.
Isolations have been made from fruiting bodies and infected root material to allow verification of their pathogenicity, to assess their clonality and pathogen dispersal and also to gauge the potential of non-pathogenic fungi collected to act as biological control agents against Ganoderma. Preliminary results support the pathogenicity of G. philippii against Acacia mangium and infrastructure is in place to carry out more rigorous tests.

Risk assessment: The same survey plots used to assess pathogen dispersal also form the backbone of the project's assessment of the role of environmental factors in determining root-rot incidence and severity.

Management options: Work has already begun on seeking out a suitable biological control from among the native fungi of Indonesia and a number of candidate organisms have already been trialled in the laboratory. One particularly promising organism with activity against two major pathogens of Acacia mangium is currently being formally identified.
In investigating alternative management solutions, observations made in Indonesia by RAPP, a project partner at a trial established by the Centre for International Forest Research (CIFOR), that removal of harvest residues reduces root rot incidence, are to be tested by imposition of an experimental burning treatment on selected survey sites.

Training and Travel: Indonesian scientists from project partner, the Indonesian Forestry Research and Development Agency (FORDA), have received training in Hobart in fungal DNA diagnostic methods and the FORDA laboratory in Jogjakarta now has the capacity to molecularly identify fungal isolates eliminating the necessity to send cultures to Australia. Training in morphological fungal identification has also been given to Indonesian project staff in Indonesia and infrastructure items have been identified without which the development of morphological diagnostic skills in project partners will be hampered.
Travel for the project has included fieldwork in Indonesia in September 2006 (Inception meeting / workshop), November 2006 (plot establishment and monitoring), February 2007 (plot establishment and monitoring) and May 2007 (first 6-monthly monitoring). Geoff Pegg and Michelle Grose from the Queensland Department of Primary industries (Forests) spent time in Hobart for project meetings and fieldwork comparing decay in urban systems with hoop pine and Acacia plantations. Hobart staff have also travelled to Queensland to assist Pegg and Gross in establishing plots in hoop pine plantations based on the survey system established in Indonesia. Indonesian staff have also travelled to Hobart for a period of training in fungal molecular biology.

Extension and adoption: The project has also enhanced the degree of communication between Research and Development arms of the partner forestry companies by fostering cooperation on a shared challenge that will benefit the village, out-grower, mill and associated communities in which they operate, as well as potentially enhancing the sustainability of their tree-growing.

Project advances are presented in line with the project's four overarching objectives:
Pathogen identity, biology and dispersal
A number of other species have been identified fruiting or associated with root rot disease in Acacia mangium including three Phellinus / Inonotus species and five Ganoderma species. Thus there is a diversity of potentially pathogenic species present on all areas surveyed. This has enabled us to alert industry to the need to test proposed management solutions against as wide a range of potential pathogens as possible.
Somatic incompatibility testing has been commenced in Yogyakarta, Indonesia. These tests show if fungal isolates collected from different trees or sites belong to the same individual allowing us to draw conclusions about the dispersal mechanism and management of the fungi in question. The project culture collection to be used for these experiments is now in excess of 2800 databased, spatially referenced isolates.
Pathogen spread is being monitored on a system of 24 semi-permanent plots on six sites across Indonesia and Northern Australia representing a broad range of site conditions and vegetation histories. All Indonesian sites have now been monitored at least twice and 4 of the 5 Indonesian sites have now been monitored three times. This is providing information on disease progression in Acacia mangium at an unprecedented level of detail which will underpin disease modelling for the remainder of the project.
Risk assessment
The value of various above-ground variables for detecting the below-ground presence of root rot on a tree has been assessed.
For individual trees, though there is a tendency for living trees with root rot to show poorer crown condition, if an individual tree has good crown condition this does not mean that root rot is not present on its roots. In fact, most living trees with root rot have healthy crowns.
Our ability to predict the disease status of a tree is markedly improved by the use of a new index developed to integrate not only the health of the individual tree but also the health of its nearest neighbours
Preliminary models have been developed (using the index mentioned above) to link the number of dead trees in root rot infected areas to the total, underlying level of infection / inoculum potential on a range of sites.
Collaboration with the ACIAR project (FST/2004/058: Realising genetic gains in Indonesian and Australian plantations through water and nutrient management) will underpin the parameterisation, validation and delivery of the model developed.
Management options
Experiments have been set up on one of the 5 Indonesian sites mapped for root rot disease to examine effectiveness of inter-rotation stump removal and remediation burns.on the spatial and temporal development of root rot disease in the subsequent crop.
Biological controls are being investigated:
The putative biological control targeted by one of our industry partners has been identified molecularly to genus and morphological identification to species is now underway.
Indigenous Indonesian fungi with antifungal and wood decomposing activity have been discovered through the project and are currently being laboratory tested to discern if these abilities could allow them to inhibit or out-compete the pathogens on dead wood.
Training, cooperation, extension and adoption
Preparations are underway for two Indonesian collaborating scientists to visit Australia to develop their skills in risk assessment and biological control.
Collaboration and cooperation in data management has been enhanced through the development of a project website including members only online-access to project data and planning tools.
Molecular training in Hobart and Yogyakarta has meant that routine molecular identification of fungal isolates can be undertaken in the Yogyakarta FORDA laboratory.
We have recommended that Industry partners integrate mechanised planting-hole preparation and biological control application and higher cost management solutions including stem injection of systemic fungicides or plant growth promoters (such as phosphite or Biosil) on high value assets such as seed orchards.
We are also investigating the relationship between root rot in Acacia mangium and the performance of Eucalyptus pellita planted on ex A. mangium lands, as the use of E. pellita as an alternative crop has been proposed as one possible management solution to the root rot problems in A. mangium. Our research into pathogens and pathogenicity is helping to assess the feasibility of this.