Italy - Spread of Xylella slowing in puglia, researchers say

By Paolo DeAndreis

Italy’s main scientific bodies dedicated to agricultural research and combating the spread of Xylella fastidiosa told parliament that the spread of the bacteria is slowing down.

″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.

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