Four olive trees have been infected by the aggressive pathogen in the Barletta-Andria-Trani province, a region responsible for nearly half of Apulia’s olive oil production.

The latest infections were confirmed by the laboratories of the Institute for the Sustainable Protection of Plants, which is part of the National Research Council (CNR).

These findings are a direct result of the extensive monitoring activities carried out in the Apulian region by local institutions, researchers, and volunteers.

Since January, nearly 250 samples have been collected and analyzed in the Bisceglie area, mostly from olive trees, along with a few from other species, such as wild cherry, which are considered susceptible to Xylella fastidiosa.

The discovery of infections north of Bari triggered a nationwide alarm, coming less than three months after the most recent Xylella outbreak found in Minervino Murge, about 60 kilometers from Bisceglie.

In both cases, the subspecies “pauca” of Xylella fastidiosa was identified; the strain has already devastated southern Puglia for over a decade.

Oronzo Antonio Milillo, president of the Apulian Federation of Agronomists, told AndriaViva magazine that the alert level is currently very high due to the specific characteristics of the infection, which are still being investigated.

“The bacterium typically spreads only a few hundred meters per day, so it’s reasonable to assume that a vector may have unknowingly transported it along the road. This is a possibility we must seriously consider,” Milillo said, referring to insects that often attach to cars and can easily be transported over long distances by unsuspecting vehicles.

In a note published on the Apulian Regional Council website, regional authorities explained that all service areas along the motorways are currently being inspected.

It is believed that the insect vectors responsible for the new infections may have traveled aboard trucks stopping at these service areas.

“On the other hand, if the spread is due to a natural movement of the vector, we should already have found, or will likely find through further testing, intermediate areas of infection. That’s why the alert level is extremely high,” Milillo added.

Twelve years after Xylella fastidiosa began infecting millions of olive trees in the southern Salento area, the new findings have reignited concerns about the potential economic consequences of a renewed outbreak.

“We are talking about an area… where olive growing is the leading open-air industry, with significant numbers of jobs and household incomes tied to the sector,” said Gennaro Sicolo, president of the Apulian branch of the Italian Farmers’ Confederation (CIA).

“If strong action is not taken immediately, the situation could spiral out of control in the metropolitan area of Bari and the province of Foggia as well,” he warned.

As prescribed by European Union regulations, a 400-meter-wide area around the infected trees is currently undergoing thorough sampling of olive trees and other Xylella fastidiosa-susceptible plants.

The infected trees will be removed through procedures designed to prevent the further spread of the bacterium. A new red zone has been declared within a 50-meter radius of the trees.

Within a 2.5‑kilometer radius around the infected areas, a buffer zone has been established, marking the area as potentially affected by Xylella fastidiosa.

This designation enables special territorial surveillance and plant monitoring. 

Within the buffer zone, strict mandatory preventive actions are being implemented, primarily aimed at preventing the spread of insects that carry the bacterium from one plant to another.

Both the CIA and the olive oil producers’ association Unapol have called for a new national plan to combat Xylella fastidiosa and to allocate more funds for the recovery of olive cultivation in the affected areas, primarily through the use of Xylella fastidiosa-resistant olive cultivars.

“The four infected olive trees are all in a roadside service area near Bisceglie. Both the trees and the land they occupy were neglected for a long time,” Giuseppe di Niso, spokesperson for the Bari chapter of the farmers’ association Confagricoltura, told BisceglieViva.

“In that area, the mandatory maintenance work was not carried out as required by current regional regulations on Xylella fastidiosa prevention,” di Niso said.

He urged people not to panic but to comply more strictly with the regulations governing preventive measures.

Those measures have already been shown to significantly slow the spread of the bacterium, for which no cure currently exists.

“I can’t say that all my fellow farmers follow the guidelines against the bacterium,” Pietro Maggi, a farmer in Barletta-Andria-Trani, told Olive Oil Times. “But I can say that awareness is growing, we all know we need to stand together if we want to contain the damage at least.”

Xylella monitoring operations conducted across the Puglia region allowed local researchers to identify an early infection, described as a “point-source outbreak.”

A point source outbreak is when an infected tree is the only one showing signs of infection among hundreds of trees tested in the area.

Local institutions confirmed that the bacterium found in Minervino Murge belongs to Xylella fastidiosa subspecies pauca, the same strain that has affected millions of Apulian trees for over a decade.

According to local authorities, the most probable cause of infection is the spittlebug, an insect considered the vector of the bacterium. Once infected with Xylella, the insect remains infective for the rest of its life.

The discovery has alarmed the local community, as the Bari province is at the heart of Italy’s most important olive-producing area.

It has been reported that the broad implementation of mandatory prevention protocols to contain the spittlebug population has considerably slowed down the bacterium.

Still, Xylella fastidiosa pauca continues heading north. Over the past decade, it has advanced approximately 250 kilometers, from the first sites where Xylella was identified to the latest infection in Minervino.

“The fear we had long expressed has unfortunately become a tragic reality. The deadly Xylella fastidiosa bacterium has reached the province of Barletta-Andria-Trani. It was at the gates of Bari, and now it’s here with us,” Gaetano Riglietti, secretary-general of the agricultural workers’ union Flai-Cgil, wrote in a statement.

While the spittlebug is known to move only short distances on its own, it is often attracted to cars and trucks; clinging to them might allow it to carry Xylella over longer distances.

Current European Union and local regulations mandate that the infected tree be removed and that an infected zone be declared within a 50-meter radius.

Before the tree is removed, the entire 50-meter area is sprayed to eradicate any potential vector insects.

Within this zone, all plants susceptible to Xylella infection are sampled. Within a 400-meter radius, extensive sampling of olive trees and other potential hosts is also conducted.

Additionally, a buffer zone, an area where special containment protocols apply, now extends 2.5 kilometers from the point of infection.

“Minervino Murge must be included among the municipalities of the Bari, Taranto and Brindisi provinces where mandatory agricultural practices must be carried out, including plowing, tilling, harrowing or shredding to reduce the population of the spittlebug,” noted the farming association Coldiretti.

In its statement, Coldiretti emphasized that mechanical and phytosanitary prevention practices, visual and insect monitoring, plant sampling and the removal of infected olive trees, along with new tools for early detection of outbreaks, are the only ways to slow the spread of the infection, since there is still no cure for this bacterial disease.

According to another farming association, CIA Puglia, current prevention measures and anti-Xylella actions are not sufficient.

“We urgently need the government to appoint a special commissioner capable of driving a real breakthrough in the plan for containment and regeneration,” wrote Gennaro Sicolo, president of CIA Puglia and national vice president of CIA Agricoltori Italiani, in a statement sent to the press.

According to Sicolo, it is time for “extraordinary resources and powers.”

“In the interest of Apulian farmers, the Puglia region and the government must work together to secure the necessary attention and resources from the European Union to fund scientific research that will finally lead to a definitive solution to stop the bacterium,” Sicolo said.

He warned that, if left unchecked, the northward spread of the bacterium could threaten the entire Apulian olive oil industry, with consequences for employment, production and even social stability.

“As a trade union organization, we are deeply concerned about the potential consequences for employment, because even limited cases like this, though hopefully isolated, still create alarm,” Riglietti said.

“Beyond that, olive growing is not only our territorial vocation; it is also a defining feature of our landscape, history and the very culture of this part of Puglia,” he concluded.

It causes the deadly Olive Quick Decline Syndrome (OQDS), which has led to widespread outbreaks in Europe over the past 15 years, and is estimated to have an annual economic impact of more than €5.5 billion.

The origins of the bacterium in Europe and globally

Xylella fastidiosa is one of only two known species of Xylella; the other is Xylella taiwanensis, which causes pear leaf scorch in Asian pears on the island of Taiwan.

An aerobic, Gram-negative bacterium that grows in the water transport tissues of plants (xylem), X. fastidiosa is known to cause numerous plant diseases worldwide. 

The bacteria can travel freely through plants via the xylem, constantly multiplying as they do so. 

Once their numbers reach a critical level, the resulting biofilm blocks the xylem, leading to water stress and deficiencies in elements such as zinc and iron, which cause many of the symptoms associated with the diseases the pathogen is linked to.

The first reports of such a disease occurred in 1892 when an unknown plague wiped out approximately 14,000 hectares (34,600 acres) of California vineyards. 

This “Anaheim disease” was later named Pierce’s disease after Newton Pierce, the bacteriologist brought in to study the outbreak. 

Pierce correctly surmised that a microscopic infectious agent caused the disease, although he was unable to isolate or identify the specific agent.

Assumed to be a virus for most of the 20th century, it was not until 1973 that X. Fastidiosa was recognized as a bacterium. It was not until 1987 that the bacterium was formally described and named Xylella fastidiosa by Wells et al. 

Since then, 696 plant species from 88 botanical families have been identified as suitable hosts for the pathogen.

Among the diseases known to be caused by Xylella are several of significant agricultural and economic importance. These include the aforementioned Pierce’s disease, which currently causes the California wine-making industry estimated annual losses of $104 (€92) million, olive leaf scorch and OQDS.

OQDS causes withering and desiccation of olive leaves, twigs and branches, preventing the trees from bearing fruit and eventually leading to the collapse and death of the tree.

Worst-case predictive models show total economic losses of up to €5.6 billion in Italy alone by 2070, and an estimated 100,000 jobs have already been lost due to outbreaks in the country.

Due to its destructive effects and its ability to rapidly adapt to new environments and hosts, Xylella fastidiosa is regulated in the E.U. as a quarantine organism. Its introduction into, and movement within, the union territory is prohibited by law.

How Xylella spreads and where it is currently found

Native to Central America, Xylella fastidiosa is transmitted between host plants by xylem-feeding insects from the Cicadellidae (leafhopper) and Cercopidae (spittlebug and froghopper) families. 

Such insects are capable of only rudimentary flight over short distances (about 100 meters), but have been recorded traveling much longer distances when carried by the wind. Bacterial transfer has also been shown to occur below ground via root grafts.

Long-distance spread most often occurs through the movement of infected plants. This is believed to be how the pathogen was introduced to Italy and other European nations.

In October 2013, Xylella fastidiosa was found infecting olive trees in the region of Puglia in southern Italy. 

This was the first time the bacterium had been reported within the European Union. The disease caused a rapid decline in olive grove yields, and by April 2015, it was affecting the whole province of Lecce and other zones of Puglia.

The subspecies involved in Italy has been identified as X. fastidiosa subsp. pauca, a strain that shows a marked preference for olive trees and warm climates. This subspecies has since been listed under the Agricultural Bioterrorism Protection Act in the United States because of its devastating potential.

In response to the Italian outbreaks, the European Food Safety Authority (EFSA) convened an extraordinary scientific workshop in November 2015. 

More than 100 scientists from around the world attended the event to identify major knowledge gaps and discuss research priorities regarding the pathogen. 

During the same month, the EFSA concluded from ongoing experiments in Puglia that grapevines were a possible reservoir of Xylella in the region.

By October 2015, the pathogen had reached Provence-Alpes-Côte d’Azur on the mainland of France, where the subspecies X. fastidiosa subsp. multiplex was found to have infected myrtle-leaf milkwort, a plant species introduced from South Africa. 

The following year, the bacterium was identified in Corsica and Germany. In 2017, it was detected on the Spanish islands of Mallorca and Ibiza, and subsequently on the Spanish mainland.

Xylella has since been found in olive trees and other host plants across the Iberian Peninsula, as well as in Lebanon and Israel in the Middle East.

The role of climate change in Xylella’s spread

Substantial research indicates that climate change increases the risk of plant disease outbreaks, with changes in temperature and humidity being the primary drivers.

As global temperatures rise, the geographic range of many pathogens expands, exposing new regions and plant species to diseases previously restricted to warmer climates. 

Higher temperatures are generally conducive to the proliferation and propagation of fungal and bacterial species, especially when combined with elevated humidity. 

Additionally, higher minimum temperatures extend the seasonally active period of organisms and increase their ability to survive the winter and persist in the environment. This applies not only to pathogens but also to their vectors.

In addition to favoring many pathogens, higher temperatures can weaken a plant’s natural defensive mechanisms through processes such as heat and water stress, making them more vulnerable to infection and more likely to suffer greater damage and higher mortality rates.

Specifically regarding Xylella fastidiosa, a recent climate-driven epidemiological model analyzed the vulnerability of European lands to the disease in different climate change scenarios by assessing the climatic conditions favored by both the pathogen and its primary vector, Philaenus spumarius, also known as the meadow froghopper or meadow spittlebug. This insect has previously been identified as the vector responsible for spreading the bacterium in Italian olive groves.

The study found that a global mean temperature rise of 1.5 °C increases the percentage of total land area at risk in Europe to 0.32 percent, while a rise of 4 °C increases the area to 1.87 percent. 

Within the range of temperature increases analyzed, a tipping point of a 3 °C increase was identified. Beyond this threshold, the researchers found that the risk of the pathogen spreading north of the Mediterranean region becomes remarkably higher, allowing it to spread rapidly into previously unaffected areas.

The authors also assert that before the mid-1990s, European climatic conditions, except those of the Mediterranean islands, most likely prevented the bacterium from establishing itself on the continent.

Efforts to control Xylella fastidiosa

As there is no known cure for diseased plants, current control measures focus on prevention and containment. 

The most effective strategy in common use requires both the comprehensive removal of infected plant matter, which can act as a reservoir for the bacterium, and the control of insect vector populations.

In addition to the complete removal of plant matter known to be infected, the EFSA recommends creating a “buffer zone” of at least 100 meters from which all susceptible plant species are also removed and destroyed.

Due to the virulent nature of the pathogen, experts recommend using protective measures when removing and transporting all organic material during this process.

The process of controlling insect vectors is similarly involved, requiring not only the elimination of the organisms themselves but also their habitats. 

This is necessary due to the polyphagous nature and multi-stage lifecycles of such insects. Philaenus spumarius, for example, is known to feed on at least 170 host plants and develops through five separate stages after hatching.

Treatment and research for Xylella fastidiosa

Combinations of changes in cropping methods, bactericidal treatments, and interventions aimed at enhancing the physiological state of the host have shown promise in impacting disease development, even to the point of allowing harvesting to resume. To date, however, none have proven successful at eradicating the pathogen in an infected plant.

Research into treatment methods is severely curtailed by Xylella’s quarantine status, especially within the E.U. Other EU restrictions include the prohibition on using antibiotics for plant protection. Fields of research, therefore, vary from one geographical region to another.

In the United States, where antibiotic use is authorized for use in plants, information is available from trials of antibiotics such as oxytetracycline, tetracycline and streptomycin in the foliar treatment of Pierce’s disease and of microinjection of oxytetracycline in the treatment of Xylella-induced leaf scorch in American elm. 

Although such trials have demonstrated remission of symptoms, none have succeeded in eliminating infection, and symptoms returned after treatment was stopped.

A major initiative within Europe is the Biovexo Project, a Bio-Based Industries Joint Undertaking (BBI-JU) Innovation Action launched in 2020 under the European Union’s Horizon 2020 research and innovation program.

Aimed specifically at combating Xylella in olive cultivation, BIOVEXO is developing two main classes of environmentally-friendly biopesticides: “X‑biopesticides,” which target the pathogen directly, and “V‑biopesticides,” which target the spittlebugs that act as the pathogen’s primary transmission vector. 

The component substances being trialed are bacterial strains, a microbial metabolite, plant extracts and an entomopathogenic fungus.

In a novel approach, recent research in Brazil involves N‑acetylcysteine, a common mucolytic drug used to treat paracetamol overdose and to loosen thick mucus in human cases of disorders such as pneumonia and bronchitis. 

While the mechanisms responsible are not yet fully understood, initial results have shown the effectiveness of the drug in disrupting bacterial biofilms when applied by irrigation to hydroponic or field crops.

Given the role that biofilms play in protecting bacteria against antimicrobial treatments and ultimately leading to bacterial resistance, this area of research may be on the rise, as breaking down the protective biofilm matrix could significantly increase the effectiveness of treatments targeting the Xylella bacterium directly.

Until a means is found to accurately and systematically kill the pathogen throughout its host, as this research suggests might one day be possible, quarantine and destruction of infected plants will likely remain the single most effective method of control.

“We are working toward a new beginning, bringing fresh energy and ideas to this land and my grandfather’s olive farm,” said Lapo Pignatelli, owner of La Falca.

Pignatelli’s olive farm is located in the heart of Salento, the Apulian region hardest hit by Xylella fastidiosa.

Paradoxically, the farm’s revitalization is funded by the same trees that dried up after being infected by the bacterium.

“When I returned to the farm after years of absence, the landscape had completely changed. Our centuries-old olive trees had died or were dying, and they had to be removed,” Pignatelli said.

During the removal operations, new ideas emerged. “I couldn’t bear that all that magnificent wood, which nurtured our land for centuries, would just be destroyed,” Pignatelli said.

“All of this needed a different approach. So, I decided to buy a sawmill to recover this wood, and that’s essentially where it all began,” he added.

This is how Tàccaru was founded, a company within the farm that processes dead olive trees and produces wood suitable for construction, decoration, design and art. Last year, Tàccaru contributed €30,000 of revenue to the company.

“We spoke with experts from the National Research Council, and they explained that dead wood cannot transmit Xylella fastidiosa and is completely safe,” Pignatelli said.

Meanwhile, new regional regulations allowed the reuse of a significant volume of high-quality wood from removed olive trees.

“This wood has extraordinary qualities. Its grain makes it visually striking; it’s hard, durable and naturally antibacterial. It already has its niche market among timber enthusiasts,” Pignatelli said.

Other regulations and initiatives enable locals to plant new olive orchards based on four olive varieties that are resilient to Xylella fastidiosa: Leccino, Favolosa, Lecciana and Leccio del Corno.

Pignatelli’s farm has restarted olive cultivation, beginning with five hectares of Favolosa and Leccino. “Then we learned about Lecciana, which can also be grown intensively,” he noted.

“One of our biggest challenges is the lack of workforce. We needed a fresh start with technology and mechanization,” Pignatelli explained.

As a result, new high-density orchards have been planted, groves that a small team can manage efficiently.

“If you want specialized workers who stay with you long-term, you need to offer more than just seasonal employment,” Pignatelli said.

Thus, the Tàccaru project helps the farm retain employees, who split their time between the orchards and the sawmill.

“We will soon invest in oleotourism,” Pignatelli added, hinting at renovation work currently underway at the family’s historic farmhouse.

“Many young entrepreneurs are restarting from similar points, replanting olive trees. There’s a new energy in the area,” he said. “This season, we hope for our first real olive harvest. Of course, we remain at the mercy of the weather.”

Similar enthusiasm drives the project initiated by the OlivaMi association, aiming to breathe new life into wood harvested from Xylella-affected trees while revitalizing the olive economy.

“The original idea behind OlivaMi came from British tourists who fell in love with Salento. They saw our region become increasingly darkened and sad year after year due to Xylella,” Chiara Nocco, community manager at OlivaMi, told Olive Oil Times.

The OlivaMi project began its initial fundraising round in January 2022 to help replant trees in Salento’s affected areas.

“The association promotes adopting olive varieties resilient to Xylella,” Nocco said. For each tree adopted, the association provides the adopter with one liter of extra virgin olive oil.

“We label each adopted tree with the adopter’s name, the tree’s name and a unique adoption code,” Nocco explained.

Funds raised support local farmers who care for these trees and finance planting new orchards throughout the region.

“Since 2022, more than 25,000 people have participated in the project, over 200 companies actively contribute and more than 40,000 olive trees have been donated to over 250 olive farmers,” Nocco said.

“The wood from the olive trees affected by Xylella, which are now being eradicated, represents an important resource that can have a valuable second life,” she added.

“We’ve collaborated with local artisans to transform some of this wood into unique items that tell the story of our territory’s resilience,” she said.

OlivaMi’s online shop features a wide range of products crafted from olive wood and other pieces used to create plaques displaying the names and logos of collaborating companies.

“Our mission is to transform and give value to every part of the olive tree, maintaining a strong connection between nature, tradition and innovation,” Nocco emphasized.

“Our association was established to support small landowners who cultivate olives out of passion, preserving traditions handed down from our parents and grandparents,” she added. “People without assistance from the state or the European Union.”

Small landowners in Salento can contact the association through a request form on its website.

“All the trees donated so far have been purchased with funds raised through adoptions by families, businesses, or through celebratory gifts,” Nocco said.

OlivaMi’s members are committed to employing the latest technologies in the field and business development.

“Technological innovation is crucial for reforestation and land enhancement, making the processes more efficient, sustainable and easier to monitor,” Nocco said.

The association utilizes advanced precision agriculture tools to monitor tree health, optimize irrigation and prevent potential diseases.

“Blockchain technology also plays an important role,” Nocco said. “We launched a spin-off project, Carborea, which enables us to generate and certify carbon credits from new olive plantings.”

According to the association, technology is pivotal in shaping a brighter future for the region. “It also makes the process more engaging, helping us involve younger generations,” Nocco concluded.

“At the beginning of this year, the Australian government noticed a scientific paper reporting Xylella had been found in walnuts in China,” Michael Southan, the chief executive of the Australian Olive Association (AOA), told Olive Oil Times. 

“As a result, they conducted further investigations and confirmed that Xylella is indeed present there,” he added.

The AOA notified its members that China had been officially regarded as a high-risk country for Xylella fastisiosa.

In response to the new situation, imported nursery stock from China that could potentially host Xylella fastidiosa will now undergo increased testing, treatment and pre-export certification.

“This means much stricter precautions around plant material entering Australia,” Southan said. “It’s now significantly harder to import plant material from China if identified as a significant or high-priority host for Xylella fastidiosa.”

Additionally, Australian authorities announced emergency measures to regulate host nursery stock at the genus level rather than the broader plant family level.

This update allows for more targeted inspections. Previously, controls were applied to all plants within an entire botanical family, including species not genuinely at risk.

Shifting to genus-level regulation enables inspections to focus exclusively on plants truly at risk.

Further measures implemented by local authorities will include revisions to trade permits.

According to Australia’s Department of Agriculture, Fisheries and Forestry (DAFF), Xylella fastidiosa “is Australia’s highest national priority plant pest. It’s an invasive bacterial pathogen causing devastating diseases in over 700 plant species.”

In a note, DAFF emphasized that “if Xylella fastidiosa were to enter Australia, eradication would be virtually impossible, as no treatment or cure exists.”

A team from Xinjiang Agricultural University in Urumqi conducted the research, which confirmed the presence of Xylella fastidiosa in several walnut tree leaves.

The scientists identified the multiplex subspecies of Xylella fastidiosa, which is considered low-risk for olive trees.

However, they did not exclude the presence of other subspecies, indicating a potential risk for various other plant species, including olives.

The bacteria can spread unnoticed for years before symptoms become evident, allowing ongoing epidemics to remain undetected for considerable periods.

Previous studies also suggest that when multiple subspecies coexist, genetic exchange is possible, potentially affecting the pathogen’s adaptation, host range and evolution.

The publication of this research alerted Australian authorities about the new risk, underscoring the lack of an active international communication channel for such developments.

“That’s interesting because considerable time passes between conducting research, writing a paper and having it approved for publication. This creates a high risk period,” Southan said.

During this period, no specific containment measures were taken.

In response to these findings, the Australian Olive Biosecurity Plan was updated. “The plan is part of Australia’s broader biosecurity strategy,” Southan said.

He noted that, for the olive industry, “we are signatories to the Emergency Plant Pest Response Deed, a documented agreement outlining our response to potential incursions of pests significantly impacting our industry or multiple industries.”

“As part of this, each signatory industry maintains a biosecurity response plan, a document informing the government and other industries about the most critical pests and diseases threatening the olive industry,” Southan added.

“It also outlines current measures to minimize the introduction of these threats and actions we would undertake if an incursion occurs, including our immediate response to reduce spread and prevent further damage,” he continued.

These biosecurity plans primarily focus on prevention and identifying potential risks at entry points such as ports and airports.

Among the identified risks are insects that could serve as vectors for the bacteria, including spittlebugs, which Australian researchers are currently studying.

“We do not have the exact insects known as Xylella fastidiosa vectors in Europe, but we have related insects within the spittlebug family that look somewhat similar,” Southan noted.

“They’re not identical, but we don’t know whether they could act as vectors if Xylella fastidiosa were introduced here,” he added, highlighting the complexity of potential scenarios.

Every year, Australia allocates increasing resources to prevent and mitigate agricultural threats. “Almost weekly, I encounter issues related to potential incursions. It’s becoming increasingly common,” Southan said.

Occasionally, threats are uncontrollable. “I recall years ago, a strain of rust affecting wheat arrived in Australia carried by the wind,” he said. “It traveled across the ocean and landed here. How can you prevent that?”

International trade in plants and goods, combined with the increased movement of people, further heightens biosecurity risks.

“Sometimes pests sneak in and escape, making it essential to have detailed procedures in place for managing new plant pests or diseases,” Southan said.

Olive Oil Times contacted the researchers in China involved in the study but did not receive a response by publication.

• Olive Biz
• Australian Department of Agriculture, Fisheries and Forestry

Authorities said the fastidiosa subspecies (Xylella fastidiosa fastidiosa) of the deadly plant pathogen was identified in two types of rockroses, two species of Cytisus plants and lavender in the hilly region of Valencia de Alcántara in the province of Cáceres.

According to the European Food Safety Authority, Xylella fastidiosa is not known to naturally infect olive trees, and authorities confirmed that no infected olive trees were identified.

The pauca and multiplex subspecies infect olive trees and cause Olive Quick Decline Syndrome, which has no cure and has been identified in other Spanish regions.

Extremaduran plant health officials also launched the eradication protocol, which includes the immediate elimination of all infected plants susceptible to the fastidiosa subspecies in a 50-meter radius, the establishment of a 2.5‑kilometer buffer zone, insecticidal treatments against vector species and the start of a surveillance program.

Extremadura is Spain’s third-largest olive oil-producing region, yielding 68,997 tons of olive oil in the 2023/24 crop year, of which 8,220 tons were produced in Cáceres.

The same fastidiosa subspecies has been present in neighboring Portugal since 2019, with multiplex subspecies identified around the northern city of Oporto in 2023.

The news of the discovery followed an announcement by local authorities on the Balearic Islands that 37 wild olive trees, known as acebuches, infected with Xylella fastidiosa pauca, were destroyed in Sencelles.

The Balearic Institute of Nature destroyed 103 susceptible trees over two hectares in the center of Mallorca, the largest island in the Mediterranean archipelago.

“Currently, the positive cases for this species are all concentrated in the area near the cemetery of this municipality,” Joan Simonet, a local councilor, told Diario de Mallorca.

“[The interventions] have allowed better containment of the bacteria, a fact that favors the conservation of the wild olive trees in good condition and helps protect the rest of the island and olive plantations from the advance of Xylella fastidiosa,” he added.

While the first pauca infections were identified in early 2024, Xylella fastidiosa was detected initially on the Balearic Islands in November 2016.

A Xylella fastidiosa multiplex outbreak in the Valencian Community is the only other active hotspot in the country.

As of April 2024, local plant health authorities reported that the bacteria had infected 26 plant species but no olive trees. They also identified three insect vectors, including the meadow spittlebug, which preys on olives.

Previous Xylella fastidiosa outbreaks in the Community of Madrid and Almería in 2018 were successfully eradicated, and the areas remain free of the bacteria.

Along with Spain and Portugal, Xylella fastidiosa has been identified in France – where authorities said it is unlikely to be eradicated – and Italy.

Since it was first identified in 2013, Xylella fastidiosa pauca has severely impacted olive oil production in Puglia, Italy’s most significant olive oil region, and contributed to the steady harvest declines from the record-high levels throughout the 1990s and 2000s.

• Extremadura regional government
• Andalusia regional government
• Diario de Mallorca

Sustainably managed intensive olive groves of resilient cultivars, emphasizing high-quality production, emerged as the goal for farmers and millers in the southern Italian region where there is a growing consensus that the deadly bacterium cannot be eradicated.

“This visit is significant, as it showcases a rare example of virtuous collaboration between researchers and stakeholders who are actively contributing to our programs,” said Donato Boscia, a leading plant virologist at the Institute for Sustainable Plant Protection of the Italian National Research Council (CNR), to Olive Oil Times.

“At this facility, there is a small olive germplasm conservation field, part of an ongoing genetic improvement program,” he added. “Additionally, there is a greenhouse funded by donations from Merum magazine readers, a climate chamber provided by Unaprol, and a new screen house funded by Save the Olives, the organization supported by Helen Mirren.”

Experts believe the new coordinated initiative offers hope for safeguarding existing olive groves and curtailing the further spread of the pauca subspecies of Xylella fastidiosa to unaffected territories.

Ten years after the emergence of the Xylella fastidiosa epidemic, which is widely believed to have triggered Olive Quick Decline Syndrome and killed millions of trees, Puglia remains the most significant olive oil-producing region in Italy.

“The presence of Xylella in the Apulian territory has reached extreme levels of complexity,” Boscia said. “New findings in central Puglia have identified other Xylella subspecies, such as Xylella multiplex, which is potentially dangerous for viticulture but not a significant issue for olives.”

“However, this complexity necessitates a multifaceted approach to containment and eradication efforts,” he added.

Farming and producer organizations such as Coldiretti, Unaprol and Cai Consorzi Agrari d’Italia have launched a project to assist olive growers in replanting Xylella-resistant varieties.

The goal is to plant around three million new olive trees, a fraction of the 21 million lost to Xylella. This initiative includes providing certified high-quality resistant plants, technical support for land preparation and specialized agronomic and phytopathological consultancy.

“The spread of Xylella has reached a point where eradication is no longer possible. We must learn to coexist with it,” said David Granieri, the president of Unaprol.

Boscia highlighted how extensive Xylella-monitoring operations have given researchers and stakeholders significant knowledge about the bacteria.

“This is the result of a surveillance program conducted by the Puglia region, which is unique worldwide, with over 250,000 analyses per year and 250 monitoring stations dedicated to vector monitoring,” he said, referring to the insect population, such as spittlebugs, responsible for spreading the bacteria.

“This activity is unsustainable in the long term and possibly even in the medium term. It is not exportable because you can’t ask other regions or countries to replicate it with the same amount of resources,” Boscia added, referring to the growing number of different strains of Xylella found throughout the Mediterranean.

“Still, those operations have provided substantial data compared to what was known a decade ago,” he noted.

Controlling vector insect populations goes hand in hand with agricultural practices and procedures that offer hope for the survival of olive trees in affected areas.

“Many native olive trees have been killed, but some have survived. If they are not severely affected, we must try to keep them alive until research enables their recovery,” said Giuseppe Lima, plant pathologist and professor at the University of Molise.

A veteran plant pathology researcher, Lima now coordinates the multidisciplinary research initiative Integroliv, which aims to counteract the effects of Xylella on olive growing in affected areas sustainably.

“To effectively counter such an insidious enemy, specific, single interventions in the region are insufficient,” he said. “Combining different approaches in complex protocols is crucial to maximize their effectiveness.”

“The new collaboration model is open to everyone,” Lima added. “Our approach aims to be a model of investigation and work, as we cannot expect a single project to encompass all possible competencies and solutions.”

“This approach ensures that new knowledge and techniques can be integrated into ongoing efforts to combat Xylella as they emerge,” he continued.

Several nationally-funded research projects, such as the Reach-Xy and Omibreed projects, aim to uncover what is behind Xylella’s genetic resilience, enhance biosecurity infrastructure, control vectors and promote sustainable water use in olive groves.

Other contributions at the event included the 1LiveXylella project, which is developing innovative technologies for Xylella diagnosis, and the SOS project, which focused on reducing the insect vector population.

“This event is a testament to the collaborative spirit of the scientific community and local stakeholders in Puglia,” Lima said. “It brings together expertise from across Europe to tackle a common challenge.”

He added that the new olive trees in Xylella-affected areas, currently represented by non-native varieties, must follow modern, rational agronomic management models to ensure their success.

These models will be based on four olive cultivars demonstrating high resistance to Xylella fastidiosa: Leccino, Lecciana, FS17 and Leccio del Corno.

“These varieties are resistant and tolerant but not immune,” Lima said. “This means we cannot be misled into thinking that, as in the past, we can simply plant olives and rely on good fortune.”

Continuous field management and monitoring will keep new semi-intensive and intensive olive plantations in good health and productivity.

“In these new forms of intensive and semi-intensive olive growing, phytosanitary problems will increase, requiring more fertilizers and phytopharmaceuticals than traditional methods,” Lima warned.

“The protocols [being developed] aim to counteract Xylella and other pathogens to keep the trees of both native and new varieties in good health and productivity,” he added.

According to Lima, the devastation caused by Xylella has harmed the Apulian landscape and identity. However, a new future can emerge from this adversity, characterized by higher-quality olive oil than in the past.

“In the Salento area, olives from those huge, magnificent trees were often traditionally collected from the ground, resulting in high acidity levels in the lampante oil,” Lima said.

“Tomorrow, with modern olive growing and the planting of rational, semi-intensive orchards, things can change,” he added.

In his view, the new groves will be able to consider the socio-economic aspects of modern olive growing, where a workforce can be hard to find and product quality becomes an essential equirement.

“Such modern olive growing will certainly lead to the production of better quality oil,” Lima said. “We are moving towards new forms of olive growing, which could bring more income to olive oil companies while contributing to the restoration of olive growing and the environment in areas affected by Xylella.”

It should be stressed that the initial studies concerning the olive decline in Salento attributed the phenomenon to a number of pathogens: the “complex” disease, including also some fungi. But, upon the identification of Xylella fastidiosa subsp. pauca, the bacterium has been retained as the sole causal agent of Olive Quick Decline Syndrome (OQDS).

Consequently, from 2015 onward, every decline symptom identified on olive trees, such as leaf, twig and branch dieback, was attributed to the bacterium, and this assumption was largely conveyed to farmers, agronomists, journalists and politicians.

During the monitoring surveys, the regional inspectors have, consequently, collected samples from olive trees that visibly show some of such symptoms just because they are suspected to be caused by Xylella fastidiosa.

By checking the data collected by the regional phytosanitary inspectors of Puglia, one question arises. If, from 2016 until 2022, the percentage of olive trees that visibly show symptoms of decline tested positive for the occurrence of Xylella fastidiosa is in a range of 22.5 percent to 3.21 percent, which other pathogens caused the symptoms in the remaining 78 to 97 percent of olive trees?

Within this scenario, it should be outlined that, in the pathogenicity tests, Xylella fastidiosa subsp. pauca causes some leaf wilting on the inoculated plants more than one year after the inoculation, whereas fungi belonging to Neofusicoccum spp., isolated in the same areas of Salento affected by the olive disease, are capable of killing the whole plant in two to three weeks (Scortchini et al., 2023).

The wide occurrence of fungi and their aggressiveness could explain the vast majority of symptomatic olive trees sampled and resulted in negative for the bacterium.

It is possible that in the infected areas of Salento, Xylella fastidiosa occurs to a great extent but what is observed is that phytopathogenic fungi are also contemporaneously present in the same tree that hosts Xylella fastidiosa.

A more comprehensive approach to the study concerning the olive decline should be to also consider other phytopathogens involved in the complex disease currently affecting olive trees in Puglia.

It should be added, that, nowadays, many pathological emergencies that affect woody species are caused by a number of phytopathogens that can act between them and in combination also with abiotic predisposing factors.

In any case, in Salento, neither Xylella fastidiosa nor OQDS could have killed “tens of millions” of olive trees, considering that in the province of Lecce, the olive trees are estimated to be “only” 11 million, and many of these are still visibly healthy and productive. Therefore, this narrative is absolutely unfounded.

A second aspect of the rebuttal concerns the low incidence of Xylella fastidiosa in the demarcated areas. We do not deny that the aim of the monitoring surveys is to find infected trees and that a low occurrence of the bacterium has to be expected within the “buffer” areas. We point out the unnecessary sacrifice of asymptomatic centennial and millennial olive trees that surround the infected one within a radius of 50 meters.

According to epidemiological models that revealed “the negligible role of the asymptomatic trees” in further spreading the disease, the additional uprooting would not seem useful.

It should also be added that the “blind” tree uprooting, irrespective of the real occurrence of the bacterium within the olive crown, appears quite obsolete, especially by taking into consideration the great number of very sensitive and reliable detection techniques recently developed for Xylella fastidiosa.

Moreover, many autochthonous olive trees in Salento, which have been infected since 2015, are perfectly healthy and productive today.

Some years ago, it was predicted that in the whole of Salento “will remain just 50 olive trees, a sort of museum of the past”.

Nowadays, such a statement appears quite far from the reality since, thanks to field management strategies that allow the olive groves to vegetate and yield, many farmers are continuing to take care of their olive groves planted with Ogliarola salentina and Cellina di Nardò.

In addition, a vast phenomenon of resilience is currently observed in Salento, also including the areas where the initial outbreak of the disease was reported.

Margherita Ciervo is a researcher and professor at the University of Foggia’s Department of Economy, Management and Territory.

Marco Scortichini is a researcher at the Council for Agricultural Research and Economics’ (CREA) research center for olive, fruit and citrus crops in Rome.

The regional administration said the data clearly show that the pauca subspecies of Xylella fastidiosa is the leading cause of Olive Quick Decline Syndrome (OQDS), which has killed tens of millions of olive trees in the region.

Before the arrival of Xylella fastidiosa, Italy routinely produced more than 500,000 tons of olive oil annually. Now, a harvest beyond 300,000 tons is considered a bountiful crop.

The data span the first monitoring operations in 2013 through 2022, and their publication comes shortly after a study published in the Journal of Phytopathology indicating that Xylella fastidiosa was responsible for only a minority of OQDS cases.

Over the past decade, Xylella fastidiosa pauca has spread across southern Puglia due to vector insects, such as the spittlebug, which carry the bacteria from one olive tree to the next.

The epidemic prompted Italian and European authorities to continuously define and update the boundaries of infected and neighboring areas, enacting numerous containment measures to prevent the spread of the bacteria.

As a result, officials said the most highly monitored parts of Puglia were along the borders of these containment zones, where the percentage of Xylella fastidiosa-infected olive trees and other plants was expected to be minimal.

As Xylella fastidiosa pauca spread north from Puglia’s southernmost peninsula, so did the borders of the infected and buffer areas.

“The goal of the monitoring operations… is not to inventory the infected plants but to anticipate the bacterium and identify and contain or eliminate new outbreaks at the outset to reduce the inoculation pressure on the disease-free zone and slow down the expansion of the infected area as much as possible,” authorities wrote in a note published on a dedicated website to monitoring the spread of Xylella fastidiosa.

“Therefore, monitoring data cannot provide indications on the frequency of the bacterium in the infected zone, as most of its surface is no longer subject to surveillance by the phytosanitary observatory,” they added.

The statement explicitly challenges the conclusions of the Journal of Phytopathology study, which found that only a fraction of the olive trees affected by OQDS were infected by Xylella fastidiosa pauca.

By assuming that OQDS killed millions of olive trees that were not infected with Xylella fastidiosa pauca, the research authors implied that the two were largely unrelated.

According to the regional authorities and leading experts in the field, this conclusion is incorrect.

“The reading of the data by the authors of that research is not reliable,” Donato Boscia, director of the National Research Council’s (CNR) Institute for the Sustainable Protection of Plants, told Olive Oil Times.

“Should we go and test olive trees in the infected area, we would find Xylella fastidiosa pauca in 90 to 100 percent of the cases,” he added.

Boscia, whose work made it possible to identify the presence of Xylella fastidiosa pauca in 2013, said the data analyzed in the study to confirm that Xylella fastidiosa is rarely present in OQDS-hit olive trees just cannot be used to reach such a conclusion.

“It is true that over ten years, about a million plants were analyzed,” Boscia said. “But almost all of them were located where the bacteria was least expected, the so-called buffer zone and the upper end of the infected area. It is normal to find very low percentages of Xylella fastidiosa pauca-infected plants there.”

According to Boscia, the authors of that study also mistakenly interpreted symptoms on monitored olive trees as proof of the presence of OQDS, which their paper compared to the presence of Xylella fastidiosa.

“If you look at the database, at some point, you will see that for each monitored plant, there is a definition of ‘symptoms present’ or ‘symptoms absent,’” he said. “That is just an indication for researchers. Symptoms present is not synonymous with Olive Quick Decline Syndrome, as my colleagues wrote in their study.”

Boscia added that the controversial study did not consider the different methods applied during monitoring operations over the years.

“If we consider data from 2015, we are talking of a period when analyses were also carried out in the areas where the desiccation of the olive trees was already clearly visible,” he said. “That means that in that year, the percentage of plants with ‘symptoms present’ could reach 70 percent.”

The data may have been skewed further by the rapid spread of the disease in the early years, leading authorities to move the buffer and containment zones farther north from areas densely populated with olive trees to those less so.

As a result, many olive trees in this area that died from OQDS were never tested for Xylella fastidiosa. “Those percentages drop to about 20 percent,” Boscia said.

“If one looks at the 2021 data, you can see that percentage dropping further. The reason is that in 2020, E.U. regulations halved the containment area to be monitored. Instead of monitoring the last ten kilometers of the red zone, it was reduced to kilometers,” Boscia added.

“If you look at the whole picture, the conclusions go in the opposite direction of what the study’s authors wrote,” he concluded. “If today, in the areas bordering the infected zone, we have a very low incidence of Xylella fastidiosa, that means that the containment strategy adopted by the European Union is working.”

For more than a decade, the prevailing wisdom had been that the Xylella fastidiosa (Xf) bacterium infected olive trees across the southern Italian region, resulting in the deadly OQDS.

However, research published in the Journal of Phytopathology found that slightly less than 23 percent of trees killed by OQDS from February 2016 to May 2017 were infected by Xf.

Between May 2021 and February 2022, slightly more than three percent of the OQDS-affected olive trees were found to carry Xylella.

If confirmed – and some scientists are skeptical – the findings imply that the strategies currently employed to contain Xf may not effectively address the spread of OQDS.

Researchers said the conclusions are based on data gathered by regional phytosanitary bodies and research institutions from 2013 to 2023.

The data include the areas monitored, the number of trees exhibiting OQDS symptoms, the number of plants examined, the number of trees testing positive for Xylella fastidiosa pauca – a strain of the bacteria that infects olive trees – and the number of plants uprooted within the designated zones in Puglia.

“Everything we wrote comes from reading those numbers,” said Marco Scortichini, lead olive and fruit crop researcher at the Italian Council for Agricultural Research and Economics (CREA), who co-authored the study.

Current methods for detecting Xylella fastidiosa have advanced, including trained dogs and drones.

“These techniques have simplified the detection of Xylella fastidiosa compared to earlier methods,” Scortichini said. “Significant research investment in recent years has led to the development of effective and highly sensitive tools.” 

Local inspectors are responsible for the monitoring tasks, selecting olive trees for sampling by specialized labs to detect Xylella fastidiosa’s presence.

“Expectations might suggest a high prevalence of Xylella fastidiosa in olive trees from infected zones,” Scortichini said. “Yet, we find ourselves at a mere 3.21 percent.”

Since its discovery in Apulian olive trees in 2013, Xylella fastidiosa has been under intense scrutiny by both regional and national authorities.

The bacterium is classified as a List‑A quarantine pathogen, indicating it was previously unidentified in the region and has caused significant damage in other areas, including the Americas.

“Current data validate initial observations, indicating that the syndrome and Xylella fastidiosa overlap only in a minority of instances,” said Margherita Ciervo, a study co-author and researcher at the University of Foggia’s Department of Economy, Management and Territory.

“This also suggests that Xylella fastidiosa is not the primary cause of the trees’ rapid demise,” she added. “Xylella fastidiosa may exacerbate the condition of trees affected by OQDS but is not the direct cause.” 

Given these findings, the researchers advocate reassessing the measures implemented to combat Xylella fastidiosa.

The existing European Union plant health law mandates the demarcation of Xylella-infected zones and the enforcement of strict eradication policies, including removing an infected olive tree and all others within a 50-meter radius.

The study’s authors argue that the eradication measures should be reconsidered in light of their findings. “Earlier studies have shown that asymptomatic olive trees barely contribute to the bacterium’s spread,” they wrote. 

In a 2020 study cited by the researchers, the asymptomatic stage was found to have low to negligible infectivity. Trees with symptoms were instead found to be able to spread Xf to an average of 19 other trees per annum.

According to Scortichini and Ciervo, suspending the 50-meter radius eradication rule “could preserve numerous healthy ancient and monumental olive trees and their significant contribution to the landscape.”

They argue that further investigation should focus on alternative causes of OQDS. “Besides a few studies on Xylella fastidiosa and other pathogens, OQDS has received little attention,” Scortichini said.

He suggested that exploring OQDS’s development could open new research avenues.

“The past decade has seen a shift from the notion of a single pathogen causing fatal disease in trees to a more complex understanding,” Scortichini said. “We’re gradually recognizing that various microbes, influenced by temperature fluctuations and climatic disruptions, can collectively lead to disease.”

He also highlighted the potential impact of climate change on soil conditions, moisture levels and plants’ resilience to drought and heat waves.

“Climate alterations might activate different pathogens that would otherwise be benign or diminish the plants’ capacity to resist them,” Scortichini concluded.

By analyzing samples taken in 136 locations, local experts found the fastidiosa subspecies (Xylella fastidiosa fastidiosa) in six almond trees. It is the first time the strain has been identified in the Italian region.

Given its potential as a pathogen for various plants, local authorities noted that containment protocols, including eradicating the infected trees, analyzing the newly found bacteria and further monitoring, will be conducted.

“The discovery of this new bacterium stems from extensive, precise and careful monitoring carried out by the agriculture department,” Donato Pentassuglia, the regional secretary to agriculture, told local media.

“At this moment, there is a need for a unity of purpose and activity to support the phytosanitary security of the region,” he added. “Now, we must extinguish the outbreak promptly by eradicating the bacterium. There is no need for alarmism, but it is necessary to remain vigilant.”

Pentassuglia said researchers still do not know how aggressive or infectious the new strain is but warned that extra precautions surrounding the pests that transmit the disease, especially those that prey on grapes, must be taken.

The infected plants identified by authorities are located outside Puglia’s red and buffer zones to contain a different strain of Xylella fastidiosa, the pauca subspecies.

Over the past decade, Xylella fastidiosa pauca has caused the death of millions of olive trees across southern Puglia.

According to the European Food Safety Authority, Xylella fastidiosa fastidiosa is not known to infect olive trees naturally. However, the subspecies is well known in the Americas for causing the deadly Pierce’s disease in several crops, such as grapevines.

Since its emergence at the end of the 19th century, Xylella fastidiosa fastidiosa has remained a significant threat to the United States wine industry.

Current models predict a modest global expansion of Pierce’s disease in the next 20 years, primarily due to the international plant trade, which expands the geographic range of the pathogen.

Difficult to detect and often identified only after a long time from the initial infection, Xylella fastidiosa is actively spread by several vector insects.

Puglia is a large wine producer and exporter. Other potential targets of the subspecies fastidiosa include almond and cherry trees, both broadly grown in the region.

Salvatore Infantino, director of the regional phytosanitary observatory, told local media that the U.S. Xylella fastidiosa epidemic and the Apulian outbreak might still follow very different paths.

“The potential aggressiveness [of the newly found strain] depends on many factors, such as the characteristics of the infected areas,” he said.

Gianluca Nardone, director of Puglia’s agricultural department, said the scientific network working with the local authorities on Xylella fastidiosa would determine the origin of the fastidiosa strain, its virulence and the potential damages it could cause to the local territory.

“Xylella fastidiosa fastidiosa is currently present in Europe, according to the EPPO Global Database, in Portugal and the Balearic Islands,” he said.

“We must eradicate the new strain of the bacterium immediately, as it is capable of attacking grapevines,” added Gennaro Sicolo, president of the Italian Confederation of Farmers (CIA). “If this were to happen, it would be a mortal blow to agriculture in Puglia.”

According to Sicolo, a comprehensive approach to the new menace must be developed “through more decisive and systematic support for scientific research, creating and strengthening an international network capable of finally finding effective solutions. Such checks will allow us to address the new danger.”

A call for local, national and European authorities to join forces to contain the impact of the bacteria came from several farming organizations.

In a note, Coldiretti Puglia, a farmers’ union, said a review of the current European regulations about plant imports should be immediately promoted, given the potential severity of outbreaks such as the infection identified in Triggiano.

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Local authorities on the Spanish island announced a new action plan against the bacteria, which causes Olive Quick Decline Syndrome and affects dozens of other plant species.

Although Xylella fastidiosa was first identified on the Balearic Islands in 2016, this is the first time that Mallorcan authorities have identified strain 53, belonging to pauca subspecies.

Xylella fastidiosa pauca is the same strain that has spread in southern Puglia since 2008, killing millions of olive trees.

The bacteria were identified in oleander and a few wild olive trees in Sencelles, a municipality in central Mallorca, the largest island of the volcanic archipelago.

The plants were destroyed as required by the Xylella fastidiosa containment protocols of the local administration, which comply with current European Union regulations.

Although the discovery is concerning, it did not surprise the local authorities, considering the impact of the bacteria on the archipelago’s vegetation over the past eight years.

“Different strains of Xylella fastidiosa are found in the Balearic Islands, affecting different host plants,” Andreu Juan Serra, the head of agricultural services at the Balearic government’s general directorate of agriculture, livestock and rural development, told Olive Oil Times.

“As of January 16th, a total of 1,566 positive samples for the Xylella fastidiosa bacterium have been identified in the Balearic Islands,” Juan Serra said.

“Thirty-eight host species for Xylella fastidiosa were found in the infected areas of the Balearic Islands,” he added, listing species including wild cherries, figs, rosemary, vines and olives.

To date, continuous monitoring by local institutions has identified 225 olive trees affected by strains of Xylella fastidiosa on the Spanish archipelago.

One hundred fifty-nine of these were found in Ibiza, 14 in Menorca, and 52 in Mallorca, where olives have grown for thousands of years.

The bacteria was also identified in 596 wild olive trees and 365 almond trees, mostly in Mallorca.

Juan Serra explained that strain 81 affects several plant species in Mallorca, and to date, only strain 80 has been found in Ibiza. “In Menorca, only the subspecies multiplex strain 81 has been detected, affecting various plants,” he added.

“The phytosanitary measures do not differentiate between subspecies, except for the newly identified subspecies strain 53 in Mallorca, which has a specific plan to determine its scope,” Juan Serra said.

The strain 53 containment plan further increases control measures by intensifying sampling in the areas where the strain was detected. The goal is to have the bacteria quickly eliminated.

It also requires officials to identify any subspecies found in samples within a 50-meter radius of the infected plant.

The insect vectors are also targeted. “Treatment against the vector in all its life stages in these areas close to the detections is also established,” Juan Serra said.

Similar procedures have been previously taken in Puglia and have significantly slowed the spread of Xylella fastidiosa.

Balearic Islands authorities are also taking steps to contain the further spreading of the bacteria.

“As indicated by the action plan, established measures include surveying, analyzing and removing all vegetation where the Xylella fastidiosa infection is detected,” Juan Serra said. “Additionally, the movement of host plant material between islands and transferring plant material off the islands is prohibited.”

“Eradicating the pathogen is impossible, and the future involves learning to live with Xylella fastidiosa,” he added.

Many activities are underway to cope with the pathogen. “Resources are being allocated to research how to combat the bacterium, identify the best practices to prevent the vector from transmitting the bacterium, study and promote varieties of olive, almond and grapevine known to show some resistance and study how the plant’s microbiome affects the bacterium,” Juan Serra said.

“This scientific knowledge will help farmers and natural resource managers establish guidelines and measures focused on minimizing the damage caused by the plant pathogenic bacterium,” he added.

Juan Serra said farmers are on the front line of stopping the spread of Xylella fastidiosa on the Balearic Islands.

“Farmers should protect their crops by practicing good agricultural practices, controlling the presence or absence of potential insect vectors of the bacterium, applying treatments against the insect vectors and keeping the ground cover free of vegetation during the breeding season of the vector,” he said.

“In other words, they should apply a series of good agricultural practices that are recommended depending on the time of year,” Juan Serra added. “Farmers should buy plant material from authorized establishments, with plants that have a phytosanitary passport as a guarantee that they are free of pests and diseases.”

According to Miguel Miralles, owner of award-winning producer Treurer on Mallorca, strain 53 is the most significant medium-term danger to the island’s olive groves.

“However, since the first cases of Xylella fastidiosa appeared, farmers and public administrations, as well as citizens in general, have shown a high level of awareness about the importance of the problem,” he told Olive Oil Times.

“With the emergence of strain 53, controls have been increased, and we hope that its expansion can be halted,” he added.

Miralles highlighted how targeted action on different levels is critical to cope with the pathogen.

“Adopting preventive measures is essential, as it is currently the best mechanism to halt its spread,” he said. “Among these measures, it is crucial to develop good practices in soil management, fertilization, pruning and irrigation. Measures to fight against vectors also must be implemented.”

“All these measures must be generalized, and the best way to do this is through properly training farmers,” Miralles added.” In turn, public administrations must invest more resources to discover new and better ways to fight the bacteria.”

Besides farmers, local authorities are also trying to raise awareness among residents, mostly about behaviors that could trigger further outbreaks.

“Training and information dissemination are provided to raise awareness about the risks of bringing in plants from different places, as they can be carriers of pests and diseases,” Juan Serra said.

“Signage in multiple languages is displayed at airports and ports to alert both the population and tourists,” he added.

The findings, published in Nucleic Acids Research, detail an innovative approach employing a benign virus that releases custom-designed small RNA molecules to selectively silence target genes without altering the plant’s genetic makeup.

This feature holds significant importance within the European Union, where regulation around genetically modified organisms (GMOs) is stringent. Consequently, the research team has submitted a European patent application to safeguard this technology jointly owned by the Spanish National Research Council (CSIC) and the Technical University of Valencia.

The technology hinges on using artificial microRNAs (amiRNAs) – minuscule RNA molecules that exhibit DNA-like characteristics but are significantly smaller.

These amiRNAs are meticulously designed to ensure high specificity, preventing unintended gene inactivation. They are derived from larger precursor molecules whose size was optimized using Arabidopsis thaliana, a frequently employed herbaceous plant in molecular biology and plant genetics research.

This method opens up possibilities for widespread adoption in the market. It has applications in enhancing crop productivity, shielding plants from diseases, and fortifying their resilience to environmental shifts.

The spray, which contains a harmless virus, is applied to the target plant. Once inside the plant, the virus multiplies and discharges the artificial RNA molecules necessary for inactivating the desired gene.

“On the one hand, we have succeeded in considerably reducing the size of the precursor molecules of the artificial microRNAs without affecting their activity,” said Alberto Carbonell, a researcher at CSIC.

“On the other hand, we have proven that we can inactivate plant genes by spraying plant extracts that include innocuous viral vectors that produce amiRNAs from minimal precursor molecules,” he added.

This technology offers a range of benefits. Firstly, a single spray application can introduce the innocuous virus and produce amiRNAs in the targeted plant tissues, eliminating the need for multiple treatments and lowering application costs.

For instance, researchers demonstrated the inactivation of genes associated with chlorophyll biosynthesis using a single spray, leading to the yellowing of affected tissues.

Carbonell said this approach could potentially revolutionize crop agriculture by selectively inactivating gene expression, enhancing crop yield and bolstering their resilience to changing environmental conditions.

Additionally, the technology could be employed to immunize crops against various pathogens, including viruses.

Silencing specific genes within olive trees can enhance their resistance to Olive Quick Decline Syndrome (OQDS), a devastating disease caused by the bacterium Xylella fastidiosa. Researchers have identified key genes within olive trees that, when silenced, could bolster their ability to fend off OQDS.

Olive trees have defense mechanisms, and researchers are exploring ways to strengthen these natural safeguards. By targeting specific genes within the olive trees themselves, researchers aim to enhance their resistance to OQDS.

The precise genes identified for silencing play a vital role in the tree’s interaction with Xylella fastidiosa. Some of these genes are involved in the tree’s response to the bacterium, influencing the severity of OQDS symptoms. By silencing these specific genes, researchers hope to alter the olive tree’s response to Xylella fastidiosa, making it more resistant to the disease.

Silencing these genes within the olive tree offers a potential solution to combat OQDS while minimizing the need for broad-spectrum pesticides. This approach would not only enhance the tree’s resistance to the disease but also contribute to sustainable and environmentally friendly agricultural practices.

Genetic analysis has demonstrated that several microorganisms provide biological advantages akin to a secondary immune system. The researchers hope their findings may allow for developing a natural biopesticide to combat the deadly pathogen Xylella fastidiosa.

Xylella fastidiosa is believed to have arrived in Italy in 2008 by introducing a single coffee plant from Costa Rica.

Xylella fastidiosa, which causes the deadly olive quick decline syndrome, has caused widespread outbreaks in Europe over the past 15 years and is estimated to have an annual economic impact of over €5.5 billion.

The bacterium has proven to be a significant challenge to manage, as there is currently no effective field control method to eradicate it.

In the research article published in Microbiology Spectrum, however, the researchers identified a group of bacteria, Bacillus spp., that they believe could hold the key to combating the pathogen.

Bacillus species have distinct characteristics that make them valuable for medical, biotechnological and agricultural applications.

They can be used in biofuel, biopolymer and bioactive molecule production. In agriculture, they can enhance plant growth, serve as biofertilizers, stimulate growth and control pathogens, making them promising for sustainable agriculture.

Bacillus-based biofertilizers enhance plant growth and yield by improving nutrient availability, nitrogen fixation, phosphorus solubilization and the production of plant growth regulators.

These bacteria can also produce antimicrobial compounds, are cost-effective and form spores for stability, offering a natural alternative to chemical pesticides.

Bacillus thuringiensis is well-known for its insecticidal properties, while other species like B. subtilis and Bacillus amyloliquefaciens have been successfully used as biocontrol agents in various commercial crops.

Moreover, the ability of some Bacillus species to produce bacteriocins, antimicrobial peptides, shows promise for plant treatment.

While these benefits have already been demonstrated in crops including wheat, sunflowers and potatoes, the research conducted by the University of Jaén team focused on analyzing their presence in Spanish olive groves and their resistance to a series of environmental challenges.

Under the supervision of Hikmate Abriouel, the team embarked on the SMART-AGRI-SPORE project, a European Marie Curie initiative aimed at developing a biopesticide to combat Xylella fastidiosa. The project involved the analysis of 417 bacteria of the genus Bacillus spp. collected from olive groves in Jaén and Málaga.

The researchers sought to identify those bacteria capable of forming spores and hibernating to overcome adverse external conditions and revive when conditions become favorable.

These spores act as a protective shield, making the bacteria resistant to extreme temperatures, radiation and harmful chemicals. To isolate those strains with this capability, the team subjected their samples to temperatures reaching 80 ºC, thus eradicating all those not meeting the criterion.

“Faced with an adverse event, such as a lack of nutrients in the environment, these bacteria enter a state of rest, like a kind of hibernation, until the danger disappears and they can resume their normal vital functions,” explained Julia Manetsberger, one of the paper’s authors.

To further understand the resistance of Bacillus spp. to environmental challenges, the researchers exposed the bacteria to varying quantities of antibiotics and inorganic fertilizers.

Their resistance was normal, similar to that of other bacterial species. This resilience suggests that Bacillus spp. would survive in nature when exposed to such commonly used agricultural compounds, continuing to impart the desired benefits to the olive grove.

The discovery of these unique bacteria in Spanish olive groves opens up possibilities for future agricultural applications.

Given that Bacillus spp. already play a central role as one of the most widely used biopesticides, their potential for novel biotechnological applications in agriculture is promising. The researchers propose the development of a natural biopesticide utilizing this group of microorganisms to combat Xylella fastidiosa outbreaks.

In addition, the bacteria have previously been shown to withstand metal exposure and remove heavy metals from soil, effectively detoxifying the environment.

Heavy metal contamination poses a significant problem for commercial agriculture and food production since plants can absorb these metals, which make their way into the food chain.

The team, therefore, examined the tolerance of their samples to a range of heavy metals. They found that the tested isolates had good tolerance, with iron being the most tolerated, followed by copper, nickel, manganese, zinc and cadmium.

This suggests that members of the olive sporobiota could potentially thrive in soils with elevated metal levels due to environmental factors or human activities.

According to the farmers organization Coldiretti, approximately 40 percent of the olives for the current season were lost in the area.

In the last decade, olive farms around Salento have been devastated by Xylella fastidiosa. New groves in the area are planted with Leccino and Favolosa, the two olive cultivars that show significant resistance to the bacteria.

“New resistant olive trees need three or four years to produce olives,” Coldrietti wrote. “And now that some olive growers can go back to harvesting the fruits after ten years of epidemic, there we go with another loss due to extreme events such as hailstorms, tornados and cloudbursts.”

The challenging situation in Puglia was among the focal points of the Fourth European Conference on Xylella, organized by the European Food Safety Authority (EFSA).

EFSA plays a crucial role in the scientific coordination of the operations against Xylella fastidiosa and supports the European Commission and member states in establishing procedures, guidelines and methods.

Ahead of the conference, the documentary movie “The Era of the Giants” was presented to the delegates. It investigates the social, economic and landscape impacts of Xyella fatidiosa in a region where the monumental olive trees had thrived for millennia.

“That is very significant, as it allows the European public to witness the devastating impact of the pathogen,” Giuseppe Stancanelli, EFSA’s plant health risk assessment team leader, told Olive Oil Times.

“Communication to the public is a key factor to ensure the success of plant health strategies,” Stancanelli added, hinting at the comic strip recently published by EFSA.

“It stresses the importance of science in developing strategies to deal with plant health threats, such as Xylella,” he said.

In collaboration with the European Commission and member states, EFSA also launched the #PlantHealth4Life campaign.

“The goal is to raise European citizens’ awareness about the importance of plant health and everyone’s responsibility to safeguard it,” Stancanelli said.

In the E.U., Italy is not the only country affected by Xylella fastidiosa. Other strains of the bacteria have been found in the Balearic Islands of Spain, Portugal and France. Insect vectors such as spittlebugs carry the pathogen from one plant to the next, infecting olive trees, almonds and dozens of other plant species.

Over the years, the Xylella fastidiosa outbreak, coupled with the growing understanding of the threat represented by the epidemic, spurred an array of E.U.-wide activities.

“Xylella is now included in the list of the main quarantine plant pathogens maintained at the E.U. level, the so-called Priority Pests,” Stancanelli said. “That brought all member countries to develop preventive contingency plans and to intensify surveillance.”

EFSA maintains the only global database of plants infected by the different Xylella fastidiosa strains.

“That supports member states in case of new outbreaks,” Stancanelli said. “It is also useful for local institutions and farmers to decide what to plant in infected areas. It also reports the varieties of plants which showed tolerance or resistance to Xylella.”

According to the conference’s conclusions, current means to curtail the spread of Xylella fastidiosa are improving as new tools are developed.

“Xylella is a global phenomenon, not merely European,” Stancanelli said. “Thanks to the advances in scientific research, new tools that allow the detection over extensive areas and advanced pest control strategies, we are seeing significant progress.”

“At the conference, it emerged how knowledge about the biology and the ecology related to the vector insects is growing,” Stancanelli said. “Not only in the Mediterranean area but also in Northern Europe.”

Current research funded by the E.U. includes work on prevention, control, ecology and society, such as the BEXYL project, as well as the development of new biocontrol solutions acting either against Xylella fastidiosa or its vector, such as the BIOVEXO project.

BEXYL and BIOVEXO co-organized the Xylella conference in collaboration with EFSA and other E.U. projects.

A large part of the efforts funded by the E.U. goes into fostering collaboration and coordination among the many national entities involved.

Key to the E.U.’s strategies is early detection. “With EFSA scientific support, all European countries are monitoring their whole territory,” Stancanelli said.

Extended monitoring operations follow EFSA guidelines and can spot new outbreaks. That allows for a quick intervention to contain further spreading.

“Significant progress has been made in the survey and monitoring systems and diagnostics, such as those for analyzing aerial and satellite images,” Stancanelli said.

“For example, if we need to monitor all of the olive farming areas in the Mediterranean region, we cannot rely on on-field visits only,” he added. “We need to be able to analyze large portions of the territories all at once. Now that technology is available.”

Other crucial aspects debated at the conference include those olive varieties that show tolerance or resistance to Xylella fastidiosa, such as Leccino.

“There is progress in the research aiming to uncover the mechanism of such resistance,” Stancanelli said. “It is of great interest, as unlocking these aspects can also allow us to find those mechanisms in other olive cultivars.”

Since it was first tried in Puglia, the grafting methods can pave the way to identify new sources of resistance to Xylella.

“In Israel, where Xylella attacked almonds, researchers identified resistant almond varieties by grafting them over infected plants, rootstocks, and observing their responses,” Stancanelli said.

“All over the world, Xylella has become a priority plant pathogen,” he concluded. “Today, scientific research and international coordination allow us to see hope in the struggle against the pathogen.”

• Coldiretti
• EFSA

The event is the result of a partnership with Sylva Foundation, a non-profit founded in 2021, aiming at the environmental regeneration of lands affected by Xylella fastidiosa through reforestation.

Last year, Burtynsky was invited to a residence in Salento by the foundation and commissioned to translate the effects of the bacterium’s spread on the Apulian landscape into photos and videos. He was then selected to receive the 25th Pino Pascali prize, awarded each year to a contemporary artist.

“Focusing on the impetuous and negligent action of man on the planet, anthropocentric phenomena become for Burtynsky the fulcrum for redefining the spirituality of nature and the precarious balance between living beings,” said the commission of experts in the explanatory statement to the award.

The artist dedicated his 40-year career to documenting humanity’s effects on the planet, and his works can now be found in the collections of the most renowned museums in the world.

Among the most popular is the multidisciplinary body of work ‘Anthropocene Project,’ combining photography, film, virtual and augmented reality and scientific research.

“The setting of the exhibition of a contemporary artist like Burtynsky in this archaeological museum makes the representation of the Xylella fastidiosa epidemic even more dramatic, enhancing the understanding of the damages caused by this plague,” Luigi De Luca, the Sigismondo Castromediano Museum’s director, told Olive Oil Times.

The ‘Xylella Studies’ works are put in close dialogue with the archaeological collection of the museum, mingling with the artifacts located along the permanent itinerary, which is divided into five sections defined as cultural landscapes of the sea, the land, the sacred, the living and the dead.

At the same time, on the external perimeter of the museum, a selection of shots taken by the photographer and artist from Salento Daniele Coricciati during the days in which Burtynsky worked in the olive groves will be displayed throughout the exhibition.

“It is not just a matter of destroying millions of olive trees, and therefore a naturalistic as well as productive heritage, since the production of extra virgin olive oil is so pivotal in Puglia, but it is also about destroying a significant piece of the cultural identity of our land,” De Luca said.

“Indeed, the set-up in the museum, alongside items that tell us how ancient and rooted the tradition and culture of olive oil are in our land and the entire Mediterranean basin, helps us reflect even deeper on the plague that our land is experiencing,” he added.

As of today, 10 years since the Xylella outbreak associated with the drying up of olive trees was discovered, more than 8,000 hectares of territory, equal to 40 percent of the region, is affected at different levels by the epidemic and containment protocols.

Still, in the last two years, the infective capacity of the bacteria decelerated, experts told Olive Oil Times in June.

• Edward Burtynsky
• ANSA

“It has been 10 years since the Xylella outbreak associated with the drying up of olive trees was discovered,” Donato Boscia, research director at the National Research Council (CNR), one of the first to identify the bacterium, told Italian representatives. “And its ability to infect is now declining.”

“In the first seven to eight years, Xylella expanded enormously,” he added. “The infection that at first encompassed 8,000 hectares multiplied its reach on the territory by 100. Today, approximately 40 percent of Puglia is affected at different levels by the epidemic and containment protocols.”

“The news is that in the last two years, the infective capacity of the bacteria decelerated,” Boscia continued. “We can see that, both by the reduction in Xylella’s ability to spread to new areas and by the slower progression of the illness in infected plants.”

CNR researchers are studying the reasons for Xylella’s deceleration. One possible reason is an environmental management strategy that has made it more difficult for the insect vectors of the bacteria, such as the marmorated stink bug, to reproduce.

Along with the olive tree, several dozen other local plant species in Puglia are susceptible to Xylella fastidiosa.

“In the first few years of the epidemic, approximately 95 percent of the vector insects monitored in several locations tested positive to the bacteria,” Boscia said. “This percentage is now down to 25 to 30 percent.”

At specific times of the year, Apulian authorities, farmers and citizens in the at-risk areas execute a series of land management actions to reduce the opportunities for the vector insects to reproduce.

“What we are seeing is that the rules against plantations that might be sensitive to Xylella and the timely destruction of the infected plants by the farmers are playing a crucial role in this changing scenario,” Boscia noted.

Both CNR and the Council for Research in Agriculture (CREA) underlined the significance of current research investigating the role of genetics in efforts to curb the spread and mitigate the economic impacts of Xylella.

“That might help us prevent or delay the further spread of the illness,” Pio Federico Roversi, director of CREA’s National Institute for Plant Protection, told Italian representatives.

Stefania Loreti, a scientist of the National Bacteriology Laboratory at CREA, told parliamentarians that the practical effects of genetic improvements to olive trees would require 10 to 15 years to bear fruit.

Italian researchers have identified the Leccino and Favolosa (Fs-17) cultivars as the only two Xylella-resistant olive trees.

“Genetic improvement is crucial, as Leccino and Favolosa are not enough to re-populate the whole Apulian olive tree landscape,” Loreti said. “We are now researching molecules able to kill the Xylella bacteria [without damaging other plant tissues].”

Local olive growers are looking increasingly at Leccino and Favolosa grafting. CNR researchers have found that these grafts allow trees otherwise sensitive to Xylella to cope with the infection successfully.

“That is part of our action against Xylella,” Emmanuel Sanarica, the award-winning producer of Ulive, told Olive Oil Times.

“The farm where we are applying our anti-Xylella strategy is within the red zone [where active Xylella infections have been identified],” Sanarica said. “That means we have limits on the varieties we can plant there, as only Leccino and Favolosa are allowed.”

“Since 2018, our goal has been to save monumental [milennary] trees that have been here for centuries, witnesses of time,” he added. “Some of them have a diameter exceeding three meters; we could not stand their demise. So we began removing their crowns and grafting Leccino and Favolosa cuttings.”

Through this type of grafting, Sanarica hopes to transition these landmarks of the Apulian landscape from susceptible to resilient and productive varieties. He expects the process to take three years.

“I personally managed the grafting, given the significance of those trees,” Sanarica said. “We have 120 trees partially or completely grafted. That happens as after the first grafting; we proceed to a few others to fully reinstate the crown of the trees.”

Sanarica emphasized how the grafting operations do not turn the ancient trees into common Leccino or Favolosa trees.

“What we are finding out is that the new fruits are greatly impacted by the vigor of those huge trees,” he said. “Their olive oil is different from what you could expect with those two cultivars; they bear a different sensorial outcome. We are very happy with the first results, and we plan to go ahead with our strategy.”

“This technique should be more considered, but I know some [farmers] are afraid to lose production,” he added. “In reality, it is a brave choice, but we need to save those trees to preserve our history and territory.”

Coldiretti and Unprol, Italy’s main farmers’ and olive oil producers’ associations, are also testing the grafting techniques as part of a broader containment and recovery project.

“What we are doing now, on 100 monumental trees, is to cut their crown and graft Leccino cuttings,” Nicola Di Noia, Unaprol’s general director, told Olive Oil Times. “We expect those trees not to bear fruit for approximately four years.”

“As of today, we do not have a cure for Xylella,” Roversi confirmed to parliament, “but an integrated approach that allows us to maintain a lower level of infection is producing results.”

“This approach also includes several kinds of treatments as well as actions to sustain the nourishment of the olive trees by taking care of the soil, which in southern Puglia is traditionally poor,” he added. Several treatments are undergoing testing.

According to Italian scientists, easy, fast, inexpensive and simple-to-use solutions to monitor the spreading of the bacteria are currently under development and partially in use.

Roversi cited some of the many monitoring tools in the field beside the laboratory, such as dogs trained to identify infected plants or single-use kits that can help the border authorities monitor the huge amount of plants being moved into and out of the region.

“Thorough monitoring of the region is crucial, as timely action is essential,” Roversi said. “It means that if an outbreak happens in a new area, it is vital to be able to identify it immediately. That outbreak might be limited to only a few plants and, if they are identified and removed in time, it can be efficiently contained.”

• Pupia News

The announcement marks the first time regional authorities have approved a multi-year plan since Xylella fastidiosa started to spread in Italy in 2013.

Apulian authorities have budgeted €7.7 million for the strategy, which confirms the location and number of infected red zones, where past Xylella fastidiosa outbreaks are constantly monitored.

One of the new plan’s critical components is improving monitoring, which has resulted in the early detection of infections.

“Monitoring is crucial in the prevention and the fight against the bacterium,” Donato Pentassuglia, Puglia’s regional secretary of agriculture, told Olive Oil Times.

“The monitoring numbers, constantly updated through our dedicated regional portal, show a significant and timely control through plant analysis conducted not by the visual approach but by deploying precise statistical sampling techniques and advanced molecular tests.” 

Local experts routinely take seven to 10 samples from olive trees and vegetation in at-risk areas for each hectare of farmland. Sampling can be more extensive if the risk is considered greater, such as in the proximity of recently discovered outbreaks.

Sampling focuses on the dozens of species susceptible to Xylella fastidiosa bacteria. 

“The more we can detect [the infection] early, make early diagnoses and quickly apply containment measures on infected plants and new outbreaks, extinguishing outbreaks by culling, the more we reduce the advance of the olive disease,” Pentassuglia said.

This kind of monitoring allows for establishing the boundaries of the infected areas, where special containment protocols are applied.

As mandated by European Union regulations, such protocols include destroying all infected trees and all surrounding vegetation in a 50 meters radius.

Within such a radius, the new plan would typically require the destruction of dozens of centuries-old trees in the Monumental Olive Tree Valley, even if not infected. However, the E.U. has made an exception to spare the culturally and historically significant trees. 

The Apulian Administrative Tribunal (TAR) recently took this idea further and said it might also spare infected trees on privately-owned land in the valley from destruction.

According to a local citizens’ committee, which supported the landowner in her legal action, the current strategies to prevent the spread of Xylella fastidiosa have resulted in desertification “with immeasurable damages to the economy, tourism, society and environment.”

Gennaro Sicolo, president of CIA Puglia, an agricultural association, told Olive Oil Times that most farmers and landowners affected by Xylella fastidiosa had accepted the deployment of the destruction protocols. Some have even proceeded to apply them on their own.

“Luckily, only a few preferred to go to court to block eradication,” he said. “The only result they get is to help Xylella fastidiosa spread further.”

The new biennial regional Xylella fastidiosa containment plan has been adopted well ahead of the spring when the insects responsible for spreading the bacteria begin to proliferate.

According to the local government, this timing will allow authorities to deploy all the containment measures as the new season approaches. Farmers agree.

“With the new plan, this year there will be enough time to make all stakeholders participate in the new containment strategies, which also means better action planning,” Sicolo said.

Pentassuglia, the regional secretary to agriculture, emphasized that beyond monitoring the infection, the local government has sustained farms affected by the epidemic and supported the olive farming regeneration by planting resilient cultivars.

However, members of CIA Puglia believe that more can be done. “In the last few years, local institutions have accelerated the containment actions, the monitoring operations and the eradication [of the infected trees] significantly,” Sicolo said. “But there is a need for quicker and more synergic action.”

“That is why we proposed the appointment of a dedicated emergency manager with full powers, extraordinary resources and means, able to enact eradications in just a few weeks after an outbreak is reported,” he added. “Xylella fastidiosa is no less an emergency than Covid-19 has been and should be treated as such.”

Sicolo emphasized how the most significant objective now for farmers and officials is preventing the spread of the bacteria farther north, which would endanger hundreds of thousands of olive groves. “Those are the areas of the excellency of Apulian olive oil production,” he said.

Among the measures enacted throughout the whole region is the mandatory removal of vegetation known to serve as habitats for the vector insect populations.

“We wonder if extraordinary funds should be transferred to farmers to help them execute these best practices,” Sicolo said. “We also wonder if the public entities that manage roads, channels, and railways have always correctly executed the containment actions provided by the regulations against the bacteria.”

The future of the Apulian olive tree heritage remains uncertain. “Currently, there is no cure for Xylella fastidiosa, which the European Food Safety Authority has confirmed based on scientific evidence,” Pentassuglia said.

“We can, however, prevent, monitor, and act promptly to reduce and block the spread through eradicating diseased plants,” he added. “And we can, as we are proceeding, invest in constant and assiduous scientific research, in field trials that will represent… new opportunities for rebirth, also through cultural diversification.”

The social, historical and emotional link between locals and olive trees has tested the resilience of more than one generation of Apulian citizens since the first outbreaks.

“The regional action and our commitment are constant to give farmers and businesses the tools to preserve the olive-growing heritage and a strategic economy for Puglia,” Pentassuglia concluded. “And above all, to create the conditions for a real revitalization in the medium-long term of our extraordinary territory.” 

Portuguese authorities have confirmed that the symptoms caused by the Xylella subspecies Multiplex have been detected in many host species, and new red zones are being established.

For the first time, the infected plants included several varieties of citrus. The updated list of infected plants released by Portuguese authorities includes olive trees, vines, cherries and peaches.

Besides those, oaks and several medicinal and ornamental plants have also been showing symptoms associated with Xylella infestation.

Seventy-seven infected species have been identified in the isolated region around Porto. In its Xylella journal, the Direction General for Nutrition and Animal Welfare (DGAV) listed thirteen areas where Xylella has been detected in the country.

While most infections are found in the country’s northern regions, they have also been spotted in central and southern Portugal.

In its last bulletin about the Xylella outbreak, DGAV noted that the presence of the bacteria was confirmed by laboratory analysis in several ashwood plants. Therefore, a new red zone was identified in the Penamacor province, in the central-eastern part of the country.

As requested by national regulations and the European Union directives aimed at curtailing Xylella fastidiosa, all infected plants have been destroyed. Treatments targeting insects considered infection vectors have also been applied.

Within the borders of the red zone, severe limits have been set on the transportation of vegetation, and it is forbidden to plant any species sensitive to the Xylella bacterium in the area.

Given the proximity of Penamacor and other regions where Xylella fastidiosa has been identified, many farmers in Spain are voicing their concern, asking for coordinated action between the two countries to halt the spreading of the pathogen.

In a note, growers in Valencian farming associations warned that the situation should not be underestimated. They expressed “extraordinary concern for the quantitative and qualitative leap forward of the Xylella spreading in our neighboring country. An infection poses an exponential risk for Spanish and European agriculture.”

While of American origin, in Europe, Xylella fastidiosa was first detected in Puglia, the southern Italian region, in 2013. From there, the subspecies Pauca, over time, has spread to millions of olive trees, contributing substantially to the deadly Olive Quick Decline Syndrome.

Xylella was identified in Portugal in 2019, but its symptoms had already been spotted in several European locations.

All Mediterranean and olive-producing countries have created monitoring operations as requested by the E.U. regulations.

As reported by Agricoltura e Mar, given the epidemic’s devastating effect, the many different strains of the Xylella bacteria have been included on the list of invasive species maintained by the European and Mediterranean Plant Protection Organization.

• DGAV
• Agronews Comunitat Valenciana
• Agricoltura e Mar

Olive oil produced by the resilient orchards adhering to the protocol created by the newly funded anti-Xylella association, “Circle of Life,” will be sold and researched.

“We have already started; this year it was our first year. We have two hundred olive trees here, and for the initiative, we produced one bottle of extra virgin olive oil for each one of the trees,” Jennifer Andreu, owner of Masseria Guadalupe in Ostuni and Circle of Life coordinator, told Olive Oil Times.

The resulting “Olio Traiana” extra virgin olive oil is named after the “Via Traiana,” the ancient Roman road that connected Brindisi to Benevento and the rest of the Roman territory.

“The goal of the association is to give value to the excellent olive oil produced by the ancient trees while protecting them and supporting those who do not have the means to adopt the protocol and save their trees,” James Kinahan, Olio Traiana and Circle of Life marketing manager, told Olive Oil Times.

The association hopes to eventually adopt a specific label for EVOOs produced by Scortichini protocol-adhering orchards. “That could also help in spreading our idea to other districts and reach other infected areas,” Andreu added.

“For the current production, we have had the intervention of the famous Mexican artist and designer Pedro Friedeberg, who authored this year’s label and helped us craft a product which also includes information about the Scortichini protocol,” Kinahan noted.

In the last seven years, several olive growers have applied the Scortichini protocol in southern Italy. Its success illustrated how a correct deployment of a specific organic product coupled with good farming practices and efficient pruning techniques could prevent and curtail the impact of the bacteria.

“We have seen the results by talking with the growers who are applying the protocol. We already organized two events with the local community, and new ones are scheduled. There is a growing interest for the protocol,” Andreu said.

The Scortichini protocol is named after the National Research Council director of research Marco Scortichini. Over the years, the protocol has been shown to halt the bacteria’s reproduction and allow the olive tree to withstand the infection.

“We had Marco Scortichini at the last event in December, with him was another researcher of the University of Bari, Francesco Porcelli, whose work is crucial in understanding the dynamics of the spreading of the bacteria. We also had the support of the local branch of the CIA-Italian farmers association, which will help Circle of Life in reaching farmers in the area,” Andreu explained.

Many local growers interviewed by Olive Oil Times confirmed that the Scortichini protocol allows even highly infected olive trees to recover and start producing again.

“On top of that, the protocol proved to be successful in curtailing highly-damaging fungi and containing the spreading of the olive fruit fly,” Andreu noted.

Andreu, born in Mexico, is teaming up with other ex-pats to save the historic Italian olive trees, which is why many of them moved to Puglia. “We are talking about plants included in the UNESCO world heritage list. When we arrived here and saw such a unique landscape, we found so many other masseria owners worried for the future of the beloved olive trees. We all felt there was a lack of guidance and currently adopted protocols were not stopping Xylella from spreading,” she added.

In the last few months, dozens of trees have been infected outside the red zone areas. Just a few weeks ago, local regional authorities expanded the territory formally considered hit by Xylella to include the new regions.

In the infected districts, authorities conduct intense monitoring operations and destroy infected olive trees. Farmers attempt to use cleaning practices to limit the opportunities for the Xylella vector insects to reproduce and contribute to the further spreading of the bacteria.

Still, just before Christmas, monitoring operations again found more infected trees outside the current red zones.

“Our goal is to give value to the olive oil of those unique centuries-old plants. And to show how the protection of the trees and of such landscape has strong economic implications,” Kinahan noted.

The next steps for the new initiative will include posting all of its information and a treatment calendar online. “That will help growers to contact us and eventually adhere to the association. It will also support them in planning in advance the deployment of the protocol the whole year through,” Andreu concluded.

• The most recent infections
• Xylella Fastidiosa Containment Protocol Proves Effective in Puglia
• Authorities in Puglia Identify New Outbreak of Xylella Fastidiosa