Xylella Fastidiosa is a plant pathogenic bacterium that represents a significant threat to agriculture in the Iberian Peninsula, affecting woody crops such as olives, grapevines and almonds. Recent research has shown that the Iberian Peninsula is particularly vulnerable to the spread of this bacterium due to its temperate climate, which favours the bioclimatic expansion of the pathogen. The spread of Xylella Fastidiosa is facilitated by insect vectors that feed on the xylem of plants and by the trade of infected plant material. The incidence of this bacterium in the Balearic Islands and its potential distribution in the peninsula suggest a high risk for regional agriculture, especially in crops of great economic and cultural value.
Xylella fastidiosa is a devastating bacterium that has wreaked havoc on economically and ecologically important crops such as olive trees, almond trees and vineyards, especially in Mediterranean regions. Recent research has highlighted the influence of climate change on the spread of this bacterium, highlighting how rising global temperatures can alter infection patterns and expand the geographic reach of the epidemic. A study led by the Spanish National Research Council (CSIC) and the University of the Balearic Islands has used advanced techniques to analyse the evolution of the bacterium over the last two decades, revealing that an increase of more than 3 degrees in the average global temperature could mark a critical point in the risk of the disease spreading to northern Europe.
Climate plays a crucial role in the viability of plant diseases, and warmer temperatures could favor more severe outbreaks. The insect “Philaenus spumarius”, commonly known as the cicada, has been identified as the main vector of transmission of “Xylella fastidiosa”. This pathogen, which clogs plant ducts and tissues, has been responsible for the death of millions of plants and significant economic losses, in olive groves in the Puglia region (Italy) as well as in the California wine sector, where it causes Pierce’s disease in grapevines.
In Europe, the detection of the bacterium dates back a decade, and until then, it was considered a pathogen restricted to the American continent. The adaptation of the bacterium to different climatic conditions and its potential to spread under various global warming scenarios pose significant challenges for agriculture and food security. Projected models suggest that, with continued increase in temperatures, the disease could spread more widely, affecting new areas and putting additional crops at risk.
In the Iberian Peninsula, Xylella fastidiosa continues to be a significant concern with devastating impacts on woody crops such as olive trees, vines and almond trees. Recently, a team of scientists led by engineer Blanca Landa has undertaken an international project to combat this bacterium, which has been compared to a “vegetable Chernobyl” due to its ability to wipe out entire crop regions.
In Portugal, the first detection of the bacteria in citrus fruits within the European Union has been reported, indicating an expansion of the pathogen.
Symptoms of Xylella on leaves
Symptoms of Xylella fastidiosa infection vary depending on the host plant species, but generally include signs of water stress such as wilting and general decline. In more severe cases, leaf and branch drying and eventually plant death are observed. Other common symptoms include interveinal chlorosis or mottling of the leaves, which indicate mineral deficiencies. A distinctive symptom is leaf or shoot scorch, where a green part suddenly dries out, turning brown while adjacent tissues remain yellow or red. Desiccation can spread rapidly, causing complete wilting and leaf drop.
Discover the gallery of symptoms of diseases caused by Xylella fastidiosa in the EPPO Global Database
In olive trees, darkening of the xylem vessels has also been observed when a cross section of the same is performed. It is important to note that “Xylella fastidiosa” can be found in a latent state in many hosts without showing symptoms, which represents a challenge for its detection and control.
The spread of Xylella fastidiosa among plants occurs primarily through two pathways: transmission by insect vectors and vegetative multiplication of infected plant material. Insect vectors, such as the foam leafhopper Philaenus spumarius, play a crucial role in this process. These insects feed on the xylem of plants, and in doing so, they can acquire the bacteria and transmit it to other healthy plants during their feeding. The bacteria multiply within the xylem vessels, obstructing sap flow and causing the characteristic symptoms of the disease.
Managing Xylella vectors
One tactic against the pest is to reduce the attractiveness of the crop to the insect through cultural practices that promote balanced plant growth, avoiding excessive vigor that can attract vectors. This includes proper management of pruning, fertilization and irrigation.
In addition, biological control methods are being researched and developed, including the use of natural enemies of the vectors, such as predators, parasites and pathogens, that can reduce the vector population in a sustainable and environmentally friendly manner. Research is also focusing on identifying natural resistance in host plants, which could lead to the development of plant varieties that are less susceptible to infection or do not allow the transmission of the bacteria by the vectors.
Control measures to prevent the spread within the European Union
The European Commission has established a protocol for action against the pest, which is summarized as follows:
Establishment of the demarcated zone
The infected zone shall have a minimum radius of 50 m around the Xylella-infected plant. The buffer zone shall have a minimum width of 5 km in the case of outbreaks subject to containment measures, 2.5 km in the case of outbreaks subject to eradication measures and 1 km in the case of isolated outbreaks where natural spread has not occurred and eradication measures have been immediately taken.
Eradication measures
Eradication measures apply to any outbreak of Xylella fastidiosa, with the exception of infected areas where containment measures are authorised (e.g. southern Apulia, Corsica and the Balearic Islands).
Within the infected zone, all infected or symptomatic plants must be removed. Plants belonging to the same species as the infected plant or other plants must also be removed. All other host plants within the 50 m infected zone must be sampled and tested for the presence of the bacteria.
Containment measures
Containment measures are applicable to southern Apulia (Italy), Corsica (France) and the Balearic Islands (Spain), since the bacteria is widely established in these areas and eradication would not be feasible.
Intensive surveillance will be established and at least the infected plants will be removed immediately. Within the 5 km buffer zone, the same provisions apply as those presented in the eradication measures.
Planting of specified vegetables in the infected area
First, those specified vegetables are grown in insect-proof production sites free of Xylella and its vectors.
Secondly, these specified vegetables preferably belong to varieties considered resistant or tolerant to Xylella and are planted in infected areas subject to containment measures.
Thirdly, the specified plants belong to the same species of plants that have been tested and declared free of Xylella on the basis of the last two years of monitoring campaign and are planted in the infected areas targeted for eradication.
Movement of plants within and outside the demarcated areas
Strict requirements apply for the movement of specified plants out of demarcated zones and from infected zones to buffer zones.
This movement is only permitted if certain conditions are met, for example if they are grown under protected conditions, samples are taken and tested before movement, and traceability requirements apply.
WE RECOMMEND YOU
The international conference on Xylella fastidiosa of the CSIC and the MAPA together with the Bexyl Project and CYTED – Ibero-American Program of Science and Technology for Development / Iberxyfas in which a decade of research is presented, addressing the challenges and future perspectives in research to mitigate its impact.
The implementation of these strategies requires close collaboration between researchers, agricultural authorities and farmers to ensure that measures are effective and applied in a coordinated manner. At ZERYA Producciones sin Residuos S.L. we believe that education and awareness about the disease and its vectors are fundamental to the success of control programs, as they allow early detection and the adoption of appropriate management practices. With climate change altering plant disease patterns, the adaptation and continuous improvement of control strategies are essential to protect agriculture and biodiversity from the threat of “Xylella fastidiosa”.
At ZERYA we are dedicated to ensuring both pesticide-free and regenerative agriculture, two practices that benefit the environment and people’s health. By investing in our crop management, we contribute to a positive impact on the crops and food that reach our tables.
If you want to know more about us or how you can enjoy waste-free food, write to us at consultations@zerya.org or call us 4 622 690 956.
