The deadly bacterium which is wiping out olive trees in Italy has now claimed up to a million trees just in the southern region of Puglia alone.
Warnings are being sounded that Portugal’s olives could be endangered.
Since the bacterium was first detected in September 2013, the affected area has gone quickly from 8,000 to 230,000 hectares.
Entire olive groves have had to be cut down.
"Some of the trees are 1,000 years old. They are part of Italy's natural heritage and we should not be left alone by the State to face this disaster," Francesco Bara, an olive oil producer, told La Stampa newspaper.
Tuscany, Umbria and Lazio have been put on high alert.
Fears are mounting that without robust action, the disease could spread to trees elsewhere in the Mediterranean, including Portugal, Spain and Greece.
"We are calling for politicians to sit up and notice what is happening and to take necessary actions," said Giovanni Melcarne, president of an oil-producing consortium in Otranto, a town in the infected area.
The Xylella fastidiosa disease, carried by an aphid, spread from the Americas to Italy.
A mile-wide cordon is planned in which grass will be cut, the soil ploughed and pesticides applied to try to halt the progression of the disease.
The bacterium is hitting at a time of an already weak harvest resulting from a cold and wet summer in which buds dropped off and fewer olives grew. Those which did grow were attacked by the aggressive Mediterranean olive fly, the maggots of which destroyed the olives.
The downturn is likely to hit thousands of jobs in a country of already high unemployment.