Two olive trees in France have been contaminated with the “olive tree killer” bacteria xylella fastidiosa, which cannot be killed directly, and which has already destroyed more than a million trees in Italy.
This is the first time that the bacteria has been seen on an olive tree in France – although the bacteria itself was picked up in the south of the country and in Corsica, in 2015.
Two olive trees have been confirmed as killed between Menton and Antibes (Alpes-Maritimes).
The bacteria’s reputation for destroying olive trees quickly in Italy has earned it the name “olive tree killer” in Italy. Now, the French ministry for agriculture has immediately taken steps in the hope of preventing its spread further in France.
Yet, there is no known way of killing the bacteria directly.
Anne Breuil, botanist and botany professor, spoke to news source 20 Minutes, saying: “This bacteria is one of the most dangerous, as there is no way of fighting against it. We can only fight the insects that transmit [the bacteria].”
These carrier insects are called “leafhoppers” (“cicadelles” in French) which look similar to aphids.
The bacteria does not only affect olive trees; it can impact more than 300 species of plant, and symptoms can sometimes take a while to appear.
Ms Breuil said that other ways of tackling the bacteria include uprooting all potential host plants of the carrier insects within 100 metres of the infected area, as a precaution. Gardening tools should also be disinfected, with a 70% alcohol solution, or diluted white vinegar.
Using pesticides to deal with the carrier insects is problematic, however, as Ms Breuil says, because “pesticides do not only kill the leafhoppers”.
Similarly, in France, the use of antibiotics as a way to fight against the carrier insects is forbidden, in a bid to avoid antibiotic resistance.
Ms Breuil said: “There is definitely something to worry about [in France]. But, throughout history…there have been serious epidemics [like this] and we have eventually found solutions, or we have changed the growing method. There are quite a few illnesses like this in the world, such as potato blight in Ireland, which are pretty inevitable.
“But we can change growing methods, or find varieties that are resistant. There is such genetic diversity that it could be totally possible. Ways of fighting it that we don’t have today, we could have later. We could find a balance in the future; but right now, the situation is quite serious.”
Xylella fastidiosa was first seen in the 1880s in California, USA, where it affected vines. It is also found across the Americas, and in Taiwan. While it cannot survive at very cold temperatures, it can be spread by contaminated produce – or the insects themselves – from one region to another.
While it can kill the olive tree itself eventually, the olives and oil the tree may produce until then remain perfectly edible. The bacteria cannot be spread to humans.