Xylella can attack grape vines but there are several strains of the bacteria, which do not necessarily cross over.
It appears to have been introduced to Italy in 2013 from an ornamental coffee plant, which came through the port of Rotterdam from Costa Rica. Since then thousands of acres of olive groves have been affected and the European Commission has urged the country to cut down all infected trees.
The infected plant found this week in France marks the first appearance of the bacteria in Europe outside Italy. French inspectors found no trace of the insects that transmit the bacteria on or around the plant at Rungis and said it would be unlikely to spread.
Earlier this month France angered Italy when it introduced a ban on plants coming from Xylella-infected areas in Europe.
Jean-Yves Rasplus, an entomologist from French National institute of agronomic research (Inra), explains how the bacteria affects plants and why France should be concerned.
Jean-Yves Rasplus: This bacteria affects the sap, preventing it from moving around to different parts of the plant. The plant dries out. It’s like it is burned. This happens quickly: for big trees, it’s a matter of months. It impacts olive trees in Southern Europe very quickly.
RFI: How is it transmitted?
J-YR: It is transmitted by leaf hoppers, tiny insects that suck the sap and transmit the disease, a bit like mosquitoes do with humans. There are several species and we don’t know which ones are transmitting the disease in Europe. Italian researchers have identified one but otherwise we do not know how many species can transmit the disease. Even cicadas could transmit it!
RFI: Now that Xylella has appeared in France, how concerned should wine growers be?
J-YR: There are different strains of the bacteria: five sub-species and several strains. Some strains attack mostly olive trees and other plants. Others attack grape vines. For the time being, there is no proof that the strain affecting olives can shift to grape vines. So, for now, there is no reason to believe that this strain affecting olives is dangerous for wine.
The one affecting coffee plants can shift to other plants, like olive trees. But again it depends on the strain. And it is important to know which one [appeared in France] before being concerned about its shift to wine.
RFI: Are you saying that France should not be concerned about bacteria coming from Italy?
J-YR: It would be nonsense to not close exchanges from infected areas to other European countries. This is a very dangerous bacteria, so you have to be careful to avoid any contamination.
But we must accurately identify which strain is which before any further discussion [on limiting trade].
RFI: So you are saying that the discovery of the diseased plant in France should be a concern but not a reason for panic?
J-YR: Exactly. Don’t panic. It shows that we need to investigate and survey the different parts of Europe. And we must intercept plants before they contaminate other plants in other countries … It is tricky to intercept plants that people bring into Europe because there are not enough means to oversee what comes in.