Learning how other countries manage HLB will help shape Australia’s response if the damaging citrus disease hits our shores, according to NSW Citrus Pathologist, Dr Nerida Donovan.

And one of the biggest lessons so far has been the importance of treating the psyllid vector with the same “respect” as the disease.

Dr Donovan, NSW Department of Primary Industries, is part of a team working to strengthen the Australian citrus industry’s biosecurity with a project focusing on graft-transmissible diseases funded by Hort Innovation.

“The program is designed to enhance the preparedness of industry and government to combat citrus disease threats,” she said.

“To be able to do that, we have developed the capability to test for citrus diseases that we have in the country and exotic diseases that are not found here yet. (The graft transmissible pathogens) are in the vascular tissue of the plants and there is no cure for them. You either prevent them or you live with them. Some diseases lead to reduced yield or they can kill your trees.”

The project works closely with the Auscitrus propagation scheme to ensure industry has access to high health status propagation material by testing their budwood and rootstock seed source trees for disease and by maintaining foundation trees (of the highest health status) in the National Citrus Repository Program, Dr Donovan said.

Huanglongbing (HLB) preparedness is a priority of this project – looking at different detection methods, expanding the diagnostic capability to other labs in Australia and participating in surveillance programs.

A Citrus Australia Citrus Pest and Disease Prevention Committee member, Dr Donovan is part of that team looking at other ways to improve HLB preparedness, as well as preparedness for other disease and pest threats which she said would be dangerous to ignore.

A focus of the HLB preparedness has been building awareness of field systems and what the vector looks like, according to Dr Donovan.

International collaboration and field work have better equipped scientists with these identification skills, but Dr Donovan said one of the challenges for the Australian industry comes from outside citrus.

“It is particularly concerning that Murraya is a preferred host of the psyllid, it is a plant you see across most Australian towns and cities, in hedges in schools, businesses and homes,” she said.

“This means the nursery industry has to be equally invested in eradication for it to be successful.”

Dr Donovan said there were many factors which determined Australia’s ability to deal with HLB.

“It would depend on where it is found, the magnitude of the spread, and how early we detect it as to how we respond and even if we are able to respond and eradicate,” she said.

Global networks critical in tackling disease

Global and domestic citrus networks are the key to tackling diseases threatening the industry and improving biosecurity, according to Dr Donovan, who is the International Organisation of Citrus Virologists (IOCV) Chair Elect.

Dr Donovan said the IOCV provided “invaluable” learning opportunities through conferences and study tours with attendees returning to Australia to share their knowledge.

These global networks also leverage Australian research through collaborations and advice.

“I work with a great team of experienced citrus scientists in NSW DPI but in Australia there’s a lack of citrus pathologists,” she said. “There are fantastic pathologists who have some experience with citrus, such as those working hard to protect our north with the Northern Australian Quarantine Strategy, but I do rely on the citrus disease specialists who I’ve met through the IOCV,” Dr Donovan said. “And all of those connections have come about by going to conferences.”

Dr Donovan said collaborative work with international colleagues such as Professor Georgios Vidalakis and his team at the University of California, Riverside and Dr Glynnis Cook, at Citrus Research International in South Africa, enable Australian pathologists to value add to existing work. .

In 2023 the IOCV conference will be held in Australia and will coincide with the Citrus Australia Technical Forum.

Formed 63 years ago, the IOCV promotes cooperative international study and sharing of knowledge of citrus diseases caused by viruses and other graft-transmissible and systemic pathogens of citrus.

Recently celebrating 21 years in her role, Dr Donovan will take over as IOCV chair in 2023.

Involvement in the global organisation supports her professional motivations of industry and environmental sustainability, with the collaboration delivering benefits at both an academic and practical level for the Australian citrus industry.

Time in the field – and meeting the growers behind the trees – is vital for gaining perspective across the production system, according to Dr Donovan. It also delivers opportunities to observe and understand the field symptoms of citrus diseases and to be able to recognise insect vectors associated with disease transmission.

When it comes to responses to disease outbreaks, such as citrus canker, Dr Donovan’s involvement taught her about the importance of working with and respecting the emergency management structure and the vast experience of the people involved, while “understanding that they rely on your specific knowledge of the industry or the disease to enhance the response outcomes”.

“It is really important to push for science-based decisions, to be the voice for industry but also understanding the economics and social science behind a lot of the decisions as well,” she said.