Bacterial disease that 'devours' olive trees is thriving in a warmer climate

Bacterial disease poses an increasing threat to the Mediterranean’s iconic crops – grapevines, olive trees, and almond trees – as global temperatures continue to rise.

The deadly bacterium known as Xylella fastidiosa, responsible for this devastation, obstructs the plants’ ducts and tissues, severely hampering their ability to thrive.

Historically confined to specific regions, this pathogen is poised to expand its territory due to the escalating effects of climate change.

Recent research conducted by the Institute of Cross-disciplinary Physics and Complex Systems (IFISC) has shed light on this alarming trend.

Bacterial disease in a changing environment

“Pierce’s disease (PD) is a vector-borne disease caused by the bacteria Xylella fastidiosa, which affects grapevines in the Americas,” wrote the researchers.

“Currently, vineyards in continental Europe, the world’s largest producer of quality wine, have not yet been affected by Pierce’s disease. However, climate change may alter this situation.” 

The study reveals that a temperature increase exceeding three degrees Celsius could critically escalate the risk of this bacterium’s establishment in areas previously considered safe, particularly impacting wine-producing regions.

This significant finding highlights a potential turning point in the management and spread of the disease, which is currently prevalent in coastal Mediterranean areas but could extend further north across Europe.

Climate as a catalyst for plant disease

The relationship between climate and the occurrence of plant diseases is intricate, with favorable temperatures playing a crucial role in triggering epidemic outbreaks.

Manuel Matías, a leading scientist in this field, emphasized that climate change is a central driver in the global distribution and intensity of plant-based bacterial diseases.

The research team has outlined how continuous temperature increases at intervals of 1.5, 2, 3, and 4 degrees Celsius could influence the spread of Xylella fastidiosa, with each scenario showing a pattern of heightened disease risk.

Economic and ecological impact

Since its first detection in Europe just over a decade ago, Xylella fastidiosa has caused substantial economic and ecological damage.

Originally seen as a pathogen restricted to the American continent, the bacterial disease has wreaked havoc in European regions, notably in Italy’s Apulia region, where it has affected 21 million olive trees.

In Mallorca, 80% of almond trees have been impacted, demonstrating the severe consequences of its rapid spread.

Predictive analysis and risk management

The researchers have developed a comprehensive model to forecast the disease’s potential spread under various warming scenarios.

The findings indicate that countries like Portugal and Greece could face significantly increased risks of infection, with projected temperature rises pushing the risk up to 47% and 63%, respectively.

Interestingly, in Spain, the second-largest wine producer globally, the risk levels might remain relatively unchanged despite the warming.

This predictive approach is invaluable for European agricultural policy, as it aids in strategizing better surveillance and mitigation efforts against the bacterial disease.

By quantifying the risk at different spatial scales – from country-wide assessments to specific wine appellations – the researchers provide crucial data that can help refine prevention strategies and manage resources more effectively.

The battle against plant bacterial disease

The experts acknowledged the limitations posed by varying microclimates within wine-growing regions, which can complicate predictions.

“Modeling disease epidemics is a complex task, as they are emergent phenomena resulting from non-linear interactions between disease components,” wrote the researchers.

“In addition, many of the processes involved in disease development also exhibit non-linear responses to changes in environmental variables.”

However, the interdisciplinary nature of the research, combining epidemiological insights with climatic models, offers a robust framework for understanding and potentially controlling the spread of this bacterial disease.

Risk of Pierce’s disease in continental vineyards

“Because Pierce’s disease has only affected vineyards on the island of Mallorca, little attention has been paid to the risk of it reaching continental vineyards. Our risk model indicates why this possibility was very low until the mid-90s, except for the Mediterranean islands,” noted the study authors.

“In this work, we clearly show that with increasing temperatures PD will become a serious threat to important wine-growing areas in southern Europe that were not previously at risk.”

As Europe grapples with the challenges posed by climate change, this research offers a glimpse into the future risks to viticulture.

By leveraging cutting-edge climatic data and innovative modeling techniques, scientists are paving the way for more informed decisions that could safeguard the future of agriculture in the region.

The study is published in the journal Scientific Reports.

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