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Journal of Economic Entomology. These insects are common across Europe and abundant in olive groves. In summer, adults fly up from the grass into the trees, feeding on sap and repeatedly infecting each tree. Last August, tests revealed that up to 80% of the insects in afflicted orBy Erik Stokstad problem, too. That October, Boscia and his chards were carrying the bacterium. “It’s colleagues confirmed the culprit was X. fasterrifying,” Martelli says. “It’s an army of ll across the heel of Italy’s boot, tidiosa and also found it in almond trees insects loaded with bullets.” centuries-old olive trees are falling and oleander growing near infected groves By October 2014, X. fastidiosa had spread victim to a devastating pathogen. in the province of Lecce (see map). The Euto an estimated 23,000 hectares. This past “It’s beyond belief,” says Brion Duffy, ropean and Mediterranean Plant Protection February, the agriculture ministry tripled a plant bacteriologist at the Zurich Organization was quickly alerted. Within its funding, to €7.6 million, for combating University of Applied Sciences in weeks, Italy banned the movement of olive the blight. (The regional government has Switzerland, who has visited the Salento saplings and other susceptible plant mateallocated another €5.9 million.) To prepeninsula and seen hectare upon hectare of rial from Lecce. vent X. fastidiosa from spreading north, desiccated, dying trees. “This is the center But the disease spread. By December authorities designated a 3-kilometer-wide of olive production in Italy, Europe, and the 2013, some 8000 hectares were in trouble. eradication strip and buffer zone spanworld, and it’s like a bomb went off.” Often entire orchards fell sick, with the largning the peninsula; workers are clearing In spite of control efforts, the disease is est and oldest trees hit hardest. “People are it of sick trees and host plants like olespreading north, threatening olive groves observing the decline of trees that were culander and will spray insecticides to kill throughout Italy and beyond and ringtivated by their parents and grandparents,” adult spittlebugs. Elsewhere, farmers have ing alarms across Europe. In January, the Boscia says. Two months later, the European plowed thousands of hectares of orchards European Food Safety Authority to kill juvenile spittlebugs. (EFSA) warned of yield losses and Some environmental groups rising costs from control measures. doubt that X. fastidiosa is the Bringing a pathogen to heel Italy declared its first national cause of the declines. They susItaly hopes that an anti-Xylella cordon will save olive trees emergency for a plant disease pect endemic fungi or leopard north of Lecce province. and appointed a special commismoths, which have plagued olives sioner with new powers. And last in the past. (Last month, EFSA month, France closed its border to issued a report dismissing this Adriatic Sea all susceptible plant varieties from theory.) The groups have rallied Salento, sparking accusations of protesters to block efforts to cull Brindisi a trade war. “It’s a quite major issick olive trees. In February, a spesue for Europe,” says Jean-Claude cial commissioner was empowGrégoire, an entomologist with the ered to enforce tree removal, and Université libre de Bruxelles. police have been called in to keep Lecce The culprit is Xylella fastidiprotesters away from chainsawSurveillance zone osa, a bacterium widespread in wielding forestry workers. Bufer zone the Americas that has been on EuYet the disease continues to adEradication strip rope’s quarantine list since 1981. vance. Last month, infected trees Infected samples Ionian Sea One strain appears to cause mild were discovered about 30 kilomesymptoms in olive groves in Caliters north of the containment zone. 25 kilometers fornia but does not kill trees. Other Quick action might eliminate this subspecies have wreaked havoc in new hotspot, Martelli says. And South American citrus groves and more measures are in the works. North American vineyards. The microbe Union banned transport of most plants An E.U. advisory committee last week reckills plants by multiplying inside vascular from the affected region, which has hurt ommended that the European Commission tissue, thereby slowly clogging their wacommercial nurseries, and required memban imports of ornamental coffee plants ter transport system. Many kinds of sapber nations to start testing for X. fastidiosa. from Costa Rica and Honduras. It also sucking insects transmit it, even from Boscia and colleagues raced to figure specified that countries should squelch new healthy-looking plants—or from hundreds out what was going on. Genetic markers outbreaks by removing infected plants and of mildly susceptible host species—making match those of a strain isolated from ornaall host plants within 100 meters. it extremely hard to contain. mental coffee plants and oleander exported At ground zero, the epidemic has taken a X. fastidiosa’s assault on Italy was unfrom Costa Rica to Europe. Infected plants grim toll, says Blanca Landa, a plant patholcovered by Donato Boscia, a plant virologist may have arrived in Italy while they were ogist with the Spanish National Research with the Italian National Research Council’s asymptomatic. In any event, European inCouncil’s Institute for Sustainable AgriculInstitute for Sustainable Plant Protection in spections and testing have been too lax, ture in Córdoba who visited Lecce in NoBari. He first observed unusual symptoms says Giovanni Martelli, a plant virologist vember. “I saw a farmer crying in his field,” in his father-in-law’s olive grove in the with the University of Bari Aldo Moro. she says. “He told me, ‘I’m taking care of my summer of 2013. Desiccated leaves clung In Italy, the primary vector is the spittleolives better than my own children.’ ” Now, to branches for several months, instead of bug Philaenus spumarius, Boscia and colhis orchard is dying. “I came back feeling falling off. Other farmers had noticed the leagues reported in August 2014 in the completely demolished,” Landa says. ■ FOOD SECURITY
Italy’s olives under siege Blight alarms officials across Europe
620
sciencemag.org SCIENCE
8 MAY 2015 • VOL 348 ISSUE 6235
Published by AAAS
ILLUSTRATION: M. ATAROD/SCIENCE
Downloaded from www.sciencemag.org on May 8, 2015
A
Journal of Economic Entomology. These insects are common across Europe and abundant in olive groves. In summer, adults fly up from the grass into the trees, feeding on sap and repeatedly infecting each tree. Last August, tests revealed that up to 80% of the insects in afflicted orBy Erik Stokstad problem, too. That October, Boscia and his chards were carrying the bacterium. “It’s colleagues confirmed the culprit was X. fasterrifying,” Martelli says. “It’s an army of ll across the heel of Italy’s boot, tidiosa and also found it in almond trees insects loaded with bullets.” centuries-old olive trees are falling and oleander growing near infected groves By October 2014, X. fastidiosa had spread victim to a devastating pathogen. in the province of Lecce (see map). The Euto an estimated 23,000 hectares. This past “It’s beyond belief,” says Brion Duffy, ropean and Mediterranean Plant Protection February, the agriculture ministry tripled a plant bacteriologist at the Zurich Organization was quickly alerted. Within its funding, to €7.6 million, for combating University of Applied Sciences in weeks, Italy banned the movement of olive the blight. (The regional government has Switzerland, who has visited the Salento saplings and other susceptible plant mateallocated another €5.9 million.) To prepeninsula and seen hectare upon hectare of rial from Lecce. vent X. fastidiosa from spreading north, desiccated, dying trees. “This is the center But the disease spread. By December authorities designated a 3-kilometer-wide of olive production in Italy, Europe, and the 2013, some 8000 hectares were in trouble. eradication strip and buffer zone spanworld, and it’s like a bomb went off.” Often entire orchards fell sick, with the largning the peninsula; workers are clearing In spite of control efforts, the disease is est and oldest trees hit hardest. “People are it of sick trees and host plants like olespreading north, threatening olive groves observing the decline of trees that were culander and will spray insecticides to kill throughout Italy and beyond and ringtivated by their parents and grandparents,” adult spittlebugs. Elsewhere, farmers have ing alarms across Europe. In January, the Boscia says. Two months later, the European plowed thousands of hectares of orchards European Food Safety Authority to kill juvenile spittlebugs. (EFSA) warned of yield losses and Some environmental groups rising costs from control measures. doubt that X. fastidiosa is the Bringing a pathogen to heel Italy declared its first national cause of the declines. They susItaly hopes that an anti-Xylella cordon will save olive trees emergency for a plant disease pect endemic fungi or leopard north of Lecce province. and appointed a special commismoths, which have plagued olives sioner with new powers. And last in the past. (Last month, EFSA month, France closed its border to issued a report dismissing this Adriatic Sea all susceptible plant varieties from theory.) The groups have rallied Salento, sparking accusations of protesters to block efforts to cull Brindisi a trade war. “It’s a quite major issick olive trees. In February, a spesue for Europe,” says Jean-Claude cial commissioner was empowGrégoire, an entomologist with the ered to enforce tree removal, and Université libre de Bruxelles. police have been called in to keep Lecce The culprit is Xylella fastidiprotesters away from chainsawSurveillance zone osa, a bacterium widespread in wielding forestry workers. Bufer zone the Americas that has been on EuYet the disease continues to adEradication strip rope’s quarantine list since 1981. vance. Last month, infected trees Infected samples Ionian Sea One strain appears to cause mild were discovered about 30 kilomesymptoms in olive groves in Caliters north of the containment zone. 25 kilometers fornia but does not kill trees. Other Quick action might eliminate this subspecies have wreaked havoc in new hotspot, Martelli says. And South American citrus groves and more measures are in the works. North American vineyards. The microbe Union banned transport of most plants An E.U. advisory committee last week reckills plants by multiplying inside vascular from the affected region, which has hurt ommended that the European Commission tissue, thereby slowly clogging their wacommercial nurseries, and required memban imports of ornamental coffee plants ter transport system. Many kinds of sapber nations to start testing for X. fastidiosa. from Costa Rica and Honduras. It also sucking insects transmit it, even from Boscia and colleagues raced to figure specified that countries should squelch new healthy-looking plants—or from hundreds out what was going on. Genetic markers outbreaks by removing infected plants and of mildly susceptible host species—making match those of a strain isolated from ornaall host plants within 100 meters. it extremely hard to contain. mental coffee plants and oleander exported At ground zero, the epidemic has taken a X. fastidiosa’s assault on Italy was unfrom Costa Rica to Europe. Infected plants grim toll, says Blanca Landa, a plant patholcovered by Donato Boscia, a plant virologist may have arrived in Italy while they were ogist with the Spanish National Research with the Italian National Research Council’s asymptomatic. In any event, European inCouncil’s Institute for Sustainable AgriculInstitute for Sustainable Plant Protection in spections and testing have been too lax, ture in Córdoba who visited Lecce in NoBari. He first observed unusual symptoms says Giovanni Martelli, a plant virologist vember. “I saw a farmer crying in his field,” in his father-in-law’s olive grove in the with the University of Bari Aldo Moro. she says. “He told me, ‘I’m taking care of my summer of 2013. Desiccated leaves clung In Italy, the primary vector is the spittleolives better than my own children.’ ” Now, to branches for several months, instead of bug Philaenus spumarius, Boscia and colhis orchard is dying. “I came back feeling falling off. Other farmers had noticed the leagues reported in August 2014 in the completely demolished,” Landa says. ■ FOOD SECURITY
Italy’s olives under siege Blight alarms officials across Europe
620
sciencemag.org SCIENCE
8 MAY 2015 • VOL 348 ISSUE 6235
Published by AAAS
ILLUSTRATION: M. ATAROD/SCIENCE
Downloaded from www.sciencemag.org on May 8, 2015
A
