Rome's majestic umbrella pines are as much part of the landscape as the ruins and cobbled streets, but they are under threat from a tiny insect invader -- the pine tortoise scale.

"If we do nothing, the pines of Rome will be destroyed by the thousands," warned agronomist Franco Milito, who estimates there are around 60,000 such trees in the city's public areas and another 30,000 on private land.

"And they are really the trees of Rome, which shape the views. We must look after them."