Plant Killer in Olive Trees Puts EU on Alert Amid Risk to Vines

A plant germ found in Europe for the first time in dying olive trees in southern Italy could potentially spread to vineyards and citrus groves, according to the European Food Safety Authority.

The bacterium, endemic to the Americas, was found near the city of Lecce in Puglia last month, EFSA wrote in a report published yesterday, after a European Union request for “urgent” scientific assistance. The germ is linked to die-back of olive trees, some more than 100 years old, over an area of about 8,000 hectares (19,768 acres), the agency said.

The germ, xylella fastidiosa, causes Pierce’s disease, which can kill infected grapevines, according to the University of California. The disease costs the state’s grape growers an estimated $105 million a year, including $47 million in lost production and replanting costs for wine makers, a 2012 study by the university found.

“This is certainly a threat, and certainly something to be alarmed about,” said Bart Thomma, a professor of plant pathology at the Netherlands’ Wageningen University. “The task now is to try and determine whether and how it’s spreading.”

The bacterium infects the woody water-transporting tissue of plants, known as xylem, and all insects in Europe feeding on sap in woody parts should be considered potential carriers, according to Parma, Italy-based EFSA.

The natural occurrence of xylella fastidiosa in the southeastern U.S. precludes profitable production of wine grapes and causes “severe” localized losses in California, according to Wallingford, England-based plant-illness researcher CABI. Peaches, plums, coffee and citrus trees are also affected, according to CABI.

Host Plants

The number of host plants in Europe is uncertain because many species would encounter the bacterium for the first time, EFSA wrote.

“There is no record of successful eradication of x. fastidiosa once established outdoors due to the broad host range of the pathogen,” EFSA wrote. The agency said controls should focus on living plants and insects shipped in plants.

The disease “could be a major problem” with “a huge scope,” according to Francesco Serafini, head of the environmental department at the Madrid-based International Olive Oil Council, who added that he needs more time to find out more about the situation.

“The big problem with bacterial infections, especially of xylem, in general you can’t fight them,” Thomma at Wageningen University said. “Epidemiologists will be asking themselves whether it can slowed down by clearing out an area.”

Uprooting, Destruction

The only recommended course of action is uprooting and destruction of the diseased trees, Raffaele Baldassarre, an Italian member of the European Parliament, wrote in Oct. 24 questions to the European Commission, asking the EU’s executive arm what financial aid could be given to affected growers.

The germ is a “very serious threat” to Europe, the European and Mediterranean Plant Protection Organization, or EPPO, wrote in an online alert. The bacterium blocks plants’ transport of water and mineral nutrients, though “numerous” wild plants such as grasses can carry xylella fastidiosa without symptoms, the Paris-based group said.

The dying olive trees in Puglia also contained various fungi, according to EPPO.

“When olive trees are dying you know there will be considerable problems,” Thomma said. “The olive tree is not generally known for its pathogens. In southern Europe there will of course be regions where grapes and olive trees are cultivated side by side.”

Italy is the world’s largest wine producer. Puglia is the country’s third-biggest wine region after Veneto and Emilia-Romagna, accounting for an estimated 14 percent of the country’s 2013 volume, government data show.

To contact the reporter on this story: Rudy Ruitenberg in Paris at rruitenberg@bloomberg.net

To contact the editor responsible for this story: Claudia Carpenter at ccarpenter2@bloomberg.net

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