Race against time to save Rome's iconic pine trees.

Rome residents may have noticed an unusually heavy carpet of pine needles, covered in sticky honeydew, under some of the city's umbrella pines, or stone pines, in recent months.

The phenomenon is the result of pine tortoise scale insects (Toumeyella parvicornis) a non-native species which infests trees and causes the spread of a sooty black mould, leading to needle loss.

In the case of healthy specimens, the tree reacts by generating new needles which, in turn, weakens the tree and exposes it to new attacks by the parasite.

In recent years the insects arrived from North America in Italy's Campania region, around Naples, quickly reaching Rome where they have already decimated pines in the southern suburbs of Mostacciano, Spinaceto and Castel di Decima.

• The Decline of Rome’s iconic Stone Pines

As a non-indigenous species, the pest has no natural predator in Italy, meaning that it can multiply and spread unchallenged by nature.

Rome councillor Ilaria Piccolo, of the centre-left Partito Democratico, has raised the alarm in the capital, stating that "50,000 pine trees" are at risk in the city, and challenging the mayor Virgina Raggi to outline what measures are in place to save them.

• The trees of Rome

"The risk of collapse threatens the safety of citizens" - Piccolo said - "and Rome risks losing an ancient tree heritage of inestimable value."

Guglielmo Calcerano, Roman spokesperson for the Greens, says that intervention is required at regional level, calling for scientific research and the use of natural methods to counteract the insects, such as the release of 'predatory' ladybirds, "which has been tested with good results for years all over the world."

For more information in English on the invasive species and its spread in Europe see factsheet from the UK's department of environment, food and rural affairs.