Root rot is an insidious killer, strangling its victims slowly, the outside world oblivious to its menace. The disease cruelly attacks a tree at its roots, cutting off its supply to water and nutrients. By the time a tree shows signs of infection above ground it is already too late to save it.

Root rot is currently a major threat to Acacia mangium – a leading tree species in forestry plantation programs in several Asian countries, including Indonesia.

Once root rot has hit an area it continues to build in the soil. In badly affected areas root rot can kill more than 50 per cent of the trees.

Costly problem

This creates a huge and costly problem for Indonesia, whose plantations exceed 1.6 million hectares and whose forest industries contribute 3.5 per cent of the country’s gross domestic product.

An accidental discovery by an Indonesian Masters student turned out to be a game-changer for the project

Associate Professor Caroline Mohammed from the School of Land and Food at the University of Tasmania has been working on a project with University colleagues Dr Morag Glenn, Dr Chris Beadle and Dr Marcus Hardie and CSIRO researchers, alongside Indonesia’s Forestry Research and Development Agency (FORDA) and other local organisations, since 2006 to find a solution to this damaging disease.

“Root diseases are among the most studied diseases of trees in the world and there are many potential approaches to their management, including chemical treatment, biological control and tree species selection,” she said.

Million hectares

Due to the sheer size of the forests in Indonesia (more than one million hectares in total) chemical and cultural approaches are simply not viable.

The team was beginning to explore new approaches for control when an Indonesian Masters student studying at the University made an ‘accidental’ discovery that turned out to be a game-changer for the project.

Australian Centre for International Agricultural Research (ACIAR) John Allwright Fellow Luciasihi Agustini was working on a separate project, looking at a different type of root rot pathogen associated with eucalypts, when she identified the fungus Phlebiopsis.

When she reported this finding to her supervisor, Associate Professor Mohammed knew immediately that it could be the piece of the puzzle they were missing.

Bio-control

The team began conducting tests in the lab, on wood blocks and in pot trials.

“We looked at the interaction between the pathogen and the bio-control and found what we had hoped for – the bio-control outcompeted the pathogen.

Finding this potential bio-control agent was a breakthrough discovery. A large aspect of the project is focused on capacity building across both Australia and Indonesia so it was fitting that an international student was a key part of the process.

The team are now testing the agent by running stump trials on-site in Indonesia and have found that the bio-control spores will colonise the stumps.

The research is part of a long-term approach. A new project to continue the bio-control work and other disease problems in Acacia mangium starts in September with $1.7 million in fresh funding from the Australian Centre for International Agricultural Research as part of the Management of Fungal Root Rot in Plantation Acacias in Indonesia project.

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