Forest biosecurity protects more than just trees

Australia has exported its acacia and eucalypt tree germplasm around the world, with plantations  providing valuable incomes for smallholder farmers across South-East Asia and Africa. Acacias, and now eucalypts, also provide the foundation for large-scale commercial plantations in countries such as Indonesia.

ACIAR-funded research is helping partner countries plan for and respond to biosecurity threats, which in turn helps Australia improve its own biosecurity preparedness, as Australian species adapt to new environments – and those environments adapt to the introduced trees.

ACIAR has two major projects underway in South-East Asia to improve forestry biosecurity practices and build capacity. Another project in Ethiopia has moved to quickly assess a devastating new threat wiping out an acacia species that has become integral to community life.

Indonesia has one of the biggest pulp plantation industries in the world, and for many years has relied heavily on Acacia mangium plantations.

However, a major infestation of the fungal diseases Ganoderma and Ceratocystis devastated both large and small plantations of Acacia mangium across the country within a few years. Acacia plantations in Vietnam also suffered significant losses to Ceratocystis.

As the vulnerable Acacia mangium was replaced with another Australian species, Eucalyptus pellita, the current project includes tree breeding as part of a preventative approach.

Dr Jeremy Brawner, University of Florida, leads this part of the project, working to identify existing diseases to which eucalypts may be susceptible in Indonesia, Vietnam and Laos.

‘This consists primarily of setting up trials with partners across South-East Asia to work towards an understanding of the pathogens’ limits and which eucalypt populations are most affected. Getting that network organised has been a big part of the project,’ said Dr Brawner.

Knowing what diseases are out there allows his team to test the susceptibility of Eucalyptus pellita and other species before outbreaks occur, and to identify germplasm with resistance that farmers can use in future plantations.

Diagnostics has been central to an ACIAR-supported project in Ethiopia, where the introduced Australian Acacia mearnsii has established itself as a species of significant ecological, economic and social importance. In recent years, it has been devastated by a disease that has wiped out smallholder plantations.

Dr Nora Devoe, ACIAR Research Program Manager, Forestry, said when the outbreaks were reported in 2021, ACIAR initiated a project to help local organisations identify what they were dealing with to better plan their response. This project was also led by Associate Professor Lawson and Dr Healey.

‘We were contacted by our colleagues in Ethiopia who said there’s some disease happening and it’s almost decimated the whole value chain of acacia,’ said Dr Healey. ‘That includes the farmers who grow it, to the people who use it for charcoal production, to the transport workers who transport the charcoal, to women who now have to walk much further to try and find firewood.’

In Ethiopia, Acacia mearnsii has become known as ‘black gold’ or ‘black sesame’ due to its many uses, as forage feed for livestock, as charcoal and fuel wood, and as a soil improver that helps to fix nitrogen. It also provides local economic and job opportunities, reducing the need for regional migration.

After being introduced from Australia in the 1990s, it grew relatively untroubled for many years, before its pests and diseases also began to find their ways to Ethiopia.

While trying to identify the disease, researchers also realised that the imported tree species had been misidentified as Acacia decurrens. Through collaboration between the Ethiopian Environment and Forest Research Institute, and the Forestry and the Agricultural Biotechnology Institute, based in South Africa, it was re-identified as Acacia mearnsii. This helped to diagnose the disease as Uromycladium acaciae, a type of wattle rust.

Associate Professor Lawson said the next steps for Ethiopia will include biosecurity initiatives to prevent the spread of disease and assessing management options in affected areas, along with preparation of management strategies to counter other invasive pests and pathogens. 

ACIAR PROJECT: ‘Managing risk in South-East Asian forest biosecurity’ (FST/2018/179), ‘Building an effective forest health and biosecurity network in South-East Asia’ (FST/2020/123), ‘Management of Acacia decurrens Pests and Diseases in Ethiopia’ (FST/2021/162)