Xylella fastidiosa
Changes in climate suitability for Xylella could create challenges for horticulture industries if an incursion of the pathogen occurs in NSW.
The bacterial pathogen Xylella fastidiosa (hereafter referred to Xylella) causes severe disease in over 700 plant hosts, which can lead to huge economic losses for horticultural producers. Xylella is a pathogen that compromises the xylem system of host plants and is transmitted between plants by xylem-feeding insects. Over time Xylella causes plant stress, leaf scorch, reduced fruit size, stunting and, eventually, plant death.
There may a significant time delay between infection and the onset of symptoms, and early symptoms may be easily confused with water stress or other factors. The asymptomatic period of Xylella varies significantly between hosts; many infected host plants remain asymptomatic, while other infected host plants rapidly deteriorate and die.
Xylella is not present in Australia but is number one on Australia’s National Priority Plant Pest list. If an incursion of Xylella was to occur, it would create major challenges for horticultural industries in NSW. The map shows sites indicative of key horticultural production regions in NSW where Xylella could be detrimental if an incursion occurred. 
National Xylella Action Plan
National preparedness is guided by the National Xylella Action Plan (2019–2029), which outlines how Australia works to prevent, detect, and respond to any Xylella incursion. The plan brings together government, industry, researchers and communities in over 60 projects, focused on strengthening diagnostics, surveillance, research, and communication.
What is the NSW DPIRD Climate Vulnerability Assessment? ⏷
Climate change is altering the biosecurity risks for many agricultural commodities across NSW. Primary producers need evidence-based information about the changing climate, and the risks and opportunities it may bring.
The NSW DPIRD Climate Vulnerability Assessments are enhancing the resilience of our primary industries by providing information and data to help the sector better plan for, and respond to, climate change. They have assessed climate change impacts for extensive livestock, broadacre and irrigated cropping, marine fisheries, forestry, horticulture and viticulture, and important biosecurity risks associated with these industries to inform sound planning, risk management and adaptation decisions.
How we assessed climate suitability ⏷
Climate projections were sourced from Climate Change in Australia’s ‘Application Ready Data’. This dataset is comprised of projections from an ensemble of 8 global climate models, each presenting a plausible future climate. Low confidence in the projected changes due to differences between the models is noted in the text. Care should be taken when interpreting these results.
The Climate Vulnerability Assessment is intended to highlight potential industry- or regional-level changes. Intermediate and high emissions scenarios were used in the assessments (RCP4.5 and RCP8.5), but these are not the only future scenarios possible. The inclusion of climate variables important to the commodities production was based on published research, expert knowledge and data quality and availability.
Climate suitability was assessed on a monthly timescale, with the reported climate suitability representing the average for a given month over all years in the dataset. This reflects the pattern of life stages for biosecurity risks and the need to determine which months are likely to pose the greatest risk to host commodities.
Learn more in the Climate Vulnerability Assessment Project Framework.
Climate impacts: what to expect
Xylella is not present in NSW, but, should an incursion occur, changes to monthly climate suitability are likely to impact horticultural production regions in 2050:
- Decreased climate suitability for Xylella is expected between November and March across large areas of western NSW. These changes are more prominent and widespread under the high emissions scenario (low to high confidence).
- Increased climate suitability for Xylella is expected between April and September across the Great Dividing Range and western NSW (low to high confidence).
The effects of Xylella on horticultural industries in NSW will depend on the following:
- if, when and where an incursion occurs,
- the future location of those industries,
- changes in production timings of susceptible host crops,
- the overlap between susceptible life stages of commodities and the lifecycle of Xylella and
- the availability and distribution of insect vectors.
Should an incursion occur, the NSW climate is unlikely to restrict year-round survival of Xylella, especially in coastal regions. Milder winters with higher minimum and mean temperatures could allow survival of Xylella through these colder months. Such persistence through winter would increase the risk of an incursion transitioning to establishment. Warmer summers, however, with higher extreme temperatures, could limit the survival and establishment of Xylella across inland regions in the future.
Due to the large number of potential hosts, horticultural and cropping industries in NSW need to consider broad-reaching Xylella education programs to raise awareness of risks and management strategies related to this pathogen.
Where can I find the climate suitability maps?
Maps of historical and future climate suitability for commodities were produced to demonstrate where in the state a commodity is likely to thrive or else be limited by future climatic conditions. The maps are provided in the Xylella Results Report (PDF, 3339.84 KB).
Xylella Factsheet
(PDF, 714.26 KB)
Xylella Results Report
(PDF, 3339.84 KB)
