Dr Nerida Donovan has been working to keep Huanglongbing (HLB), commonly called citrus greening, out of Australia while also preparing for its arrival for nearly 25 years.
The plant pathologist, who works for the NSW Department of Primary Industries and mentors with The Crawford Fund Laos program, inspects citrus trees, working with local officers to collects samples for testing.
This has enhanced her ability to recognise, diagnose, and manage these diseases and vectors while increasing the ability of industry and government in both Australia and Laos to manage biosecurity threats.
The results inform local officers of diseases faced by their smallholders and enable the validation of diagnostic tools for exotic citrus diseases in Australian laboratories, which ultimately benefits Laos and Australia.
"It was a bit of a journey to plant pathology," Dr Donovan said.
"I grew up on the outskirts of southwestern Sydney (Campbelltown was on the edge back then) and went to a selective high school where agriculture was compulsory, but fortunately, I loved it.
"I then did a Bachelor of Science in Agriculture at the University of Sydney, majoring in Horticulture, a PhD in soil ecology and somehow secured a position as a plant pathologist.
"I studied some plant pathology-related subjects at university, but I did not focus on them.
"In my current role (since June 1999), I have mainly learned plant pathology by working on citrus diseases, but my background in horticulture and soil health has been an advantage."
Disease symptoms can often be confused with other disorders.
Seasonal differences, poor soil conditions or management practices may be having a greater impact, although pathogens may be present as secondary invaders.
Dr Donovan said industry funding was tight for many years, so NSW DPI scientists sought alternative ways to maintain their research programs.
Dr Donovan worked on projects funded by the Australian Centre for International Agricultural Research (ACIAR), which is when she came to realise the benefit not only to the stakeholders in the partner country but also to Australian growers and scientists.
"I see this work as a win-win," she said.
"When I was approached to be an e-mentor and assist with Crawford-funded work in Laos led by Professor Lester Burgess, I jumped at the chance.
"The Crawford Fund programs are lower budget but have a big impact, with targeted work either standing alone or value-adding to larger programs."
Over the years, Dr Donovan has coordinated a citrus pathology program that enables government and industry to combat citrus biosecurity threats and supports industry sustainability.
"This is achieved by having the capability to detect all described citrus diseases, understanding the diseases within our borders to minimise their impact, and preparing for the arrival of new diseases," she said.
"I provide scientific input to Australian and international teams working on multidisciplinary citrus projects where we look at practical, low-cost changes to improve productivity and livelihoods for farmers and their workers.
"This includes providing opportunities for women, such as nursery propagation businesses run from their homes in Pakistan."
Nerida has just returned from the seventh International Research Conference on Huanglongbing held in California where 430 delegates from more than 20 countries gathered to discuss this one disease and its vector.
As chair of the International Organisation of Citrus Virologists (IOCV), representing scientists working on all citrus diseases, Nerida and her team are organising a conference to be held in Mildura in March 2025, which will be attended by citrus disease experts from around the globe.
Dr Donovan said the Australian citrus industry is very proactive in the biosecurity space to prevent and prepare for citrus greening.
Dr Donovan is involved with many of those activities, such as the Citrus Australia Citrus Pest and Disease Prevention Committee, the CitrusWatch biosecurity program, educational resources to build awareness of the symptoms and vectors, and an industry-funded diagnostic program ensuring we have the best detection tools available for all biosecurity threats, not just HLB.
"In addition to the preparedness work onshore, working in international development gives Australian scientists experience with exotic disease threats and their vectors, making them better equipped to advise industry and government," she said.
"This work also gives us access to samples of the disease for validation or development of diagnostic tools in Australian laboratories.
"It is critically important to be able to make an efficient and accurate diagnosis of a suspect sample if the disease breaches our borders.
"We also do not want tests which generate false positives, potentially triggering unnecessary domestic or international trade barriers."
The knowledge Dr Donovan has gained from her international research has enabled her to provide advice to industry and government, improving preparedness for citrus greening.
"It has also assisted with the development of resources, such as fact sheets and presentations at industry forums on various exotic threats," she said.
"Improved recognition of pests or disease symptoms increases the chance of early detection, which in turn increases the likelihood of eradication.
"The diagnostic methods that we validate or develop are published so that they are accessible for use in other diagnostic laboratories or for inclusion in National Diagnostic Protocols, allowing diagnosticians to pick up an informative guide on what to do with a sample that comes into the lab potentially infected with a quarantinable pathogen.
"This can avoid delays in a response effort and can make or break the ability to eradicate a new disease.
"The diagnostic methods are also used to test sources of citrus propagation material, such as budwood and rootstock seed, supplied to nurseries by the Auscitrus propagation scheme, to keep our orchards free from nasty viruses and viroids that are known to occur in Australia."
Dr Donovan said a common similarity she has noted between overseas and Australian farmers was that they "know their land and their crops better than anyone".
"In that sense, they are the same," she said.
"We bring our technical knowledge and work with farmers and local scientists to learn from each other and improve their production systems.
"However, the farmers in Laos have not had the same educational opportunities as those in Australia, and Australian citrus growers will often travel to other regions or countries to get ideas on how to improve their business, which is beyond the reach of farmers in Laos."
Dr Donovan said it was motivating to see the impact of a project in an overseas farming community.
"When practical, low-cost changes are implemented in the nursery or orchard, it can improve tree survival and productivity," she said.
"In one example, we taught a nurseryperson a new budding technique in Australia.
"They went back and taught their workers, which led to greater bud take.
"Other small improvements in the nursery led to greater tree survival so farmers were then willing to pay more for the trees.
"The nurseryman was supporting several families, his own and those of his workers, so the benefit was great."
Dr Donovan said she has learnt a great deal from working in international research and development, in a professional and personal sense.
"It is motivating to see the impact of the work, and it helps to provide perspective and force innovation - such as how to do lab work without a fancy lab," she said.
"I have enjoyed all the projects for different reasons, but it always comes down to people for me.
"Life is richer when we connect with people from different backgrounds and lifestyles and realise that often our values are aligned; we are all just trying to 'do good'.
"It has always been a big takeaway for me."
- The Spotlight on Scientists series showcases our ag scientists' valuable work in Australia and in developing countries.
