A deadly disease estimated to have killed a million olive trees in Italy has spread to France.

The French agriculture ministry announced the discovery of the bacterium Xylella fastidiosa, known as olive tree leprosy, on two trees in the south of the country and said the infected trees would be destroyed to stop it spreading.

Ministry officials said the two decorative olives were found to have the same subspecies of the disease that killed an estimated 1m valuable ancient olive trees in Italy. All trees and plants vulnerable to the bacterium within a three-mile radius are to be destroyed and burned.

There is no known cure or prevention for the disease, which blocks the plant or trees’ ability to take up water. Michel Dessus, the president of the chamber of agriculture in the Alpes-Maritimes, where the two infected trees were discovered, said more tests were needed before swathes of vegetation were destroyed. “Cutting down trees more than a hundred years old needs to be thought about,” he told French television.

The disease, also called olive quick decline syndrome, which scientists believe affects more than 350 plant species, has also hit vineyards in north and south America. It was first detected in Europe in October 2013 when ancient olive trees in Puglia, Italy, began to die. Entire olive groves of more than 230,000 hectares have been cut down.

Although it has been found in other plants in France and the French Mediterranean island, Corsica, it is the first time the disease has hit French olive trees that, like those in Italy, have been hit by a subspecies of the bacterium called Pauca.

In July 2016, there was an isolated infestation in an oleander plant in a commercial nursery in Saxony, but the disease was declared eradicated after the plant and those around it were destroyed.

The disease is spread by insects feeding on the sap of the plants. It can also affect fruit trees including peaches, pear and plums and nuts.

The European Plant Protection Organization has declared Xylella fastidiosa a “very serious threat to the European region”. Its effects worsen during hot, dry periods in summer when there is already a lack of water. Scientists believe the cooler climate in northern Europe deters the disease.

The EU has provided funding for two big research projects into how to combat the the disease, which the European commission describes as “one of the most dangerous plant bacteria” in the world “causing a variety of diseases, with huge economic impact for agriculture, public gardens and the environment”.

It wrote: “Transmission of the disease in the EU takes place through cicada vector insects that are widespread in the entire union territory. As a consequence, the risk that this pest is spreading further to other parts of the EU is very high unless strict control measures are taken immediately after any new outbreak is detected.”

It advised members of the public not to bring any plants back from certain infected areas of the EU and elsewhere “unless accompanied by a phytosanitary or plant passport”.