One of southern Europe’s most important staples, olive oil, is under pressure from a potentially deadly disease that new research shows could infect nearly all of the productive areas of Italy, Greece and Spain.

Economic losses could be as high as €5bn over the next 50 years for Italy, where at least 1m trees have already died, if nothing is done to halt the spread of the disease and olive groves are not replanted, the study found. In Spain, losses could total €17bn over the same period, and Greece could suffer to the tune of about €2bn.