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Climate change stimulates the olive-eating ba

Philaenus spumarius

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Philaenus spumarius

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Credit: Elke Freese/Wikimedia Commons

Xylella fastidiosathe deadly pathogenic bacteria that have already wiped out millions of plants of emblematic Mediterranean crops such as grape wine, olive trees and almond trees by clogging their canals and plant tissues, will get a boost from climate change in relevant wine-producing regions where the risk is currently low. Researchers from the Institute of Cross-disciplinary Physics and Complex Systems (IFISC), a joint center of the Spanish National Research Council (CSIC) and the University of the Balearic Islands (UIB), have developed a new technique to characterize the risk of establishment of Pierce’s disease, and using state-of-the-art climate data, have obtained predictions of the future expansion of the disease under different scenarios due to global warming. Researchers from the Institute of Physics of Cantabria (IFCA), a joint center of the CSIC and the University of Cantabria, collaborated on the work. These findings were recently published in a study in the scientific journal Scientific reportsdescribe how an increase of more than 3 degrees in global average temperatures compared to pre-industrial levels would be a “turning point in the risk” of establishment of the bacterium, which is currently attacking crops in coastal areas of the Mediterranean and spreading spreads further north in Europe.

The climate determines the area in which these diseases can occur, therefore a favorable temperature favors the development of epidemic outbreaks. Scientist Manuel Matías, from IFISC-CSIC-UIB and author of this study, considers climate change a key factor in the “impulse and spread of diseases in plants around the world”. The team led by Matías has delimited the contagious effect of X. fastidiosa in four different stages of sustained temperature increase predicted for the coming years: an increase of 1.5, 2, 3 and up to 4 degrees, compared to pre-industrial levels. The pattern of increased risk of disease onset due to temperature increase is repeated in all scenarios.

A global epidemic with millions of losses

Just a decade has passed since the first detection of the X. fastidiosa bacterium in Europe, which until the 21st century was officially considered a pathogen limited to the American continent. In California (United States), this bacterium causes the deadly Pierce’s disease in grapevines, causing millions of dollars in losses annually in the wine industry. Infected plants produce few, poor-quality fruits, their leaves discolor, necrotize and fall off, and the plants may die within a few years, especially if they are not watered, which is the rule in many Mediterranean areas. For the analyzed European outbreaks, salivary bugs belonging to the family Aphrophoridae, in particular the meadow cone bug, Philaenus spumarius, are considered the most important vector. The rapid spread of the disease has already led to the destruction of crops in Italy (21 million olive trees in the Apulia region), and is also responsible for the uprooting of thousands of almond trees in the Balearic Islands (in Mallorca along the region). has affected an estimated 80% of almond trees) and in several districts in the province of Alicante.

The research, which can be accessed here, shows how the long-term rise in temperature expands the spread of water X. fastidiosa further north of the originally affected areas close to the Mediterranean Sea, with France, Italy and Portugal being the most affected countries. The study also points to a decline in the insect P. spumariusalthough marginal in some areas, such as much of Spain, which would slightly increase the ecological niche in the more continental or mountainous areas of Europe.

Researchers consider climate change to be one of the biggest challenges for EU agricultural policy. They claim that predicting what could happen in certain regions will help make better decisions in the future, increasing surveillance in these areas and reducing the disease’s potential impact on crops. For this reason, scientists have quantified the risk X. fastidiosa infection at different spatial scales; at the level of country, appellation and famous wine plantations. Based on an analysis of the risk area per country, the scientists have gathered how, in an initial scenario predicting a temperature increase of 1.5 degrees Celsius, Portugal and Greece are at the highest risk of infection, with 12% and 2% more respectively. .

A scenario that, with an extra 4 degrees Celsius, would lead to a ‘staggering’ risk, they admit, of 47% to 63%. The authors describe how France and Italy would also experience a ‘relevant’ risk in this scenario, albeit lower. In the case of Spain, the second largest wine producer, they clarify that the risk would remain similar to current levels. A situation that contrasts with some areas with designation of origin, where a rise of more than 2 degrees would seriously endanger the wine harvest, such as those in the south-east of France; the Penedés, in Spain; including the Portuguese Bairrada or Tuscany in Italy. This data can be consulted online on the IFISC website, accompanied by a detailed analysis by designation of origin, risk types, scenario according to temperature increase, and also organized by country and geographical area.

The designation of origin does not escape the attention of the ‘fastidiosa’

The authors admit the limitations of their model, which works with climate projections, when confronted with the complexity of the microclimates found in some wine-growing regions. Nevertheless, they believe it is important to try to understand how the disease spreads, hence the interdisciplinary origins of the research, which brings together epidemiological and climatological models. The study concludes by arguing that the new information will help better manage prevention resources by prioritizing areas based on their risk of infection. A way for Europe, despite the uncertainty, to make better decisions and effective strategies to reduce the risks of Pierce’s disease. A way, say the scientists, to secure the future of viticulture in the face of climate change.

Giménez-Romero, Alex; Iturbide, Maialen; Moralejo, Eduardo; Gutierrez, José M.; Matias, Manuel A. Global warming significantly increases the risk of Pierce’s disease epidemics in European vineyards. Scientific reports. DOI: 10.1038/s41598-024-59947-y

IFISC communications / CSIC communications

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