When faba bean gall disease was identified in Ethiopia a decade ago, surveys showed that 50–100% of crops quickly became infected. What followed was complete crop failure in many instances.
Today, the story is very different. Work to identify the correct pathogen has helped to develop targeted control and management strategies. This now includes a fungicide seed dressing that has vastly reduced disease levels.
This ACIAR-funded research project is a good example of how a better understanding of pests and diseases is an essential part of developing effective management practices. In turn, this brings important biosecurity benefits to Australia and its partners.
A similar approach as part of another ACIAR-funded project is also helping to counter a more recent pest incursion – fall armyworm – and create more targeted management options for farmers.
Dr Eric Huttner, ACIAR Research Program Manager, Crops, said that both ACIAR-supported projects showed what could be achieved, especially when genetic solutions, such as resistant material, were still being sought. ‘Crop management can often be the only option farmers have to keep pest and disease levels below economic thresholds.’
Faba bean gall disease
Faba bean is of critical importance to food security in Ethiopia, where it has been cultivated for millennia.
Dr Asnakech Tekalign Beyene, a plant pathologist and breeder at the Ethiopian Institute of Agricultural Research, said the pulse crop was used:
- as a protein source
- as animal fodder
- to fix atmospheric nitrogen thereby maintaining
- soil fertility
- to reduce soil-borne diseases and as an income source.
Until recently, strategies to control and manage faba bean gall disease were based on the incorrectly identified pathogen Olpidium viciae, which belongs to a genus generally restricted to underground parts of the plant. Instead, the correctly identified pathogen, Physoderma, is an above-ground pathogen primarily spread by rain splash.
The project team behind the correct diagnosis included the University of Western Australia (UWA), the New South Wales Department of Primary Industries, and researchers from the Ethiopian Institute for Agricultural Research, Debre Birhan Agricultural Research Center in Ethiopia, and the International Center for Agricultural Research in the Dry Areas (ICARDA) in Morocco.
UWA Professor Martin Barbetti said management strategies could now be aligned with the pathogen’s nature and behaviour, which is important in managing biosecurity risks. ‘We can now predict when the zoospores will be released and other intervention strategies to reduce reinfection cycles and disease severity.’
Dr Asnakech, the project’s co-principal investigator, said the diagnostics to correctly identify the pathogen had proved crucial. ‘Without properly identifying the causal pathogen and knowing the pathogen’s genetic variability and diversity, disease control efforts can be a waste of time and money or lead to further plant losses.’ But with this new knowledge, Dr Asnakech said the right fungicide seed dressing could be applied and has proved successful.
Since its first reported detection in western Africa in 2016, the invasive fall armyworm has also been widely detected in Africa, Asia and Australia. It is now spreading through the Pacific region.
However, recent genomic studies undertaken via an ACIAR-supported project have provided the foundational work needed to develop integrated pest management plans and challenge previous population classifications.
Historically, fall armyworm has been classified as either rice-preferred or corn-preferred, alluding to both the pests’ preferred food source and genetic diversity.
Research, led by Dr Wee Tek Tay from CSIRO, has instead confirmed significant genetic differences between these 2 classifications. It also led to the realisation that the worm’s spread was due to multiple independent introduction events, not only in western Africa but also in eastern Africa, Asia and South-East Asia.
These diverse pest populations have had varied responses to insecticides. The knowledge gained from the research has helped inform pest management strategies, cautioning against an over-reliance on strategies based solely on western African fall armyworm populations. Instead, it highlighted the need to undertake regional insecticide bioassay studies to increase regional biosecurity preparedness and responses.
Fall armyworm is capable of damaging maize, sorghum, cotton, ginger, rice, barley and sugarcane. In Vietnam, Dr Nguyen Van Liem from the Vietnam Plant Protection Research Institute said that when fall armyworm was first officially recognised in 2019, corn growers were very concerned. ‘However, thanks to the instruction and guidance from local plant protection agents, several control measures were applied, and it was quickly controlled.’
He said using the information learned in the ACIAR-supported project, the country was now working to identify fall armyworm migration within its northern provinces, determining natural enemies, and researching other management measures.
The fall armyworm project had many partner organisations in Indonesia, Vietnam, Laos, Myanmar, Cambodia, the Philippines, Malaysia and Uganda. It was also funded by the Grains Research and Development Corporation, Cotton Research and Development Corporation, FMC Australasia and Corteva Agriscience, and supported by Sugar Research Australia.
ACIAR PROJECTS: ‘Faba Bean in Ethiopia – mitigating disease constraints to improve productivity and sustainability’ (CIM/2017/030), ‘Characterisation of Spodoptera frugiperda (fall armyworm) populations in South-East Asia and Northern Australia’ (CROP/2020/144)