This scientific illustration shows two olive branches, one (a.) in a healthy state and another (b.) infested by the Xylella Fastidiosa bacteria.
The magnifying circle (c.) reports the difference between healthy and infested xylem vessels of an olive leaf, observed by electron microscopy. The bacteria, transported by Xylella-positive spittlebugs (Philaenus spumarius), accumulates in the xylem vessels, impairing the water uptake in the plant, therefore causing desiccation of leaves and branches.
In 2013 olive trees were greatly affected in the Apulia region of Italy, where they were attacked by the subspecies Xylella fastidiosa pauca, causing the death of over 1 million olive trees.