Rome’s iconic pines, hit hard by a nasty parasite, now face their own pandemic.

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ROME — This city’s iconic pine trees, a feature of the landscape as historic as the Colosseum itself, are being choked to death by a foreign bug. And only shots and boosters seem to have a chance at saving them.

“I’m calling it a plant pandemic,” environmental activist Francesca Marranghello said of the trail of death that the thick-hided, brownish, sap-sucking invader is leaving in its wake. If the parasite, the North American pine tortoise scale, isn’t stopped, she fears “Rome will no longer look the same.”

The bug started making its way into the country around 2015 after first landing in Naples — probably unloaded from a cargo ship at the busy seaport, though that’s still unproven. From there, it sped northward, catching a ride on birds and gusts of wind.

“The pine tortoise scale has been exploiting a veritable highway of pine trees along the coast, finding its way into a city stacked with them,” said Roberto Scacchi, another Rome-based activist. Last summer’s dry, hot conditions allowed it to spread across most of the metropolitan area. Its natural predators, including ladybugs and some micro-wasps, have failed to keep it contained.

Scacchi estimates that at least 70 percent of the local pines are infected — visibly so, as needlelike leaves turn yellow and then drop.

Many Romans are increasingly concerned about the trees’ fate. These towering, umbrella-shaped denizens are so deeply ingrained in the history and scenery here that it’s rare to find a photo or a painting of the city from any of its many eras that doesn’t show them in the background. Brought from Turkey in ancient times, they now are so inherently Italian that some people call them Italian stone pines.

“Such a grand tree rivals, in dignity, with buildings,” said Carlo Blasi, a plant ecologist at Rome’s La Sapienza University.

Classical music has even been composed to celebrate the pines, with the most famous being the symphonic poem for orchestra that Ottorino Respighi completed in 1924.

“They have a huge historic and cultural importance, not just botanical,” said Blasi, who is “very worried” about their prognosis. “You can’t just get rid of them — it would compromise a very important aspect of our city’s landscape.”

The tiny pine tortoise scale, flocking by the millions on a single plant, sucks the trees’ lifeblood and coats its leaves and bark in a treacly honeydew. The substance can be so overflowing that people walking under a sick tree will feel their shoes sticking to the sidewalk.

And in another insult, the shiny film attracts molds that turn the bark and foliage black, preventing the leaves from processing sunlight. Essentially, the bug first debilitates its victim, then suffocates it.

A pine may agonize for a decade or die within just a couple of years as other parasites also attack it. “It’s a bit like AIDS. . . . It won’t kill you on its own — secondary pathologies will do it,” explained Paolo Audisio, a professor of zoology and entomology at La Sapienza.

The rescue operation is ramping up across the city, especially through private efforts.

On a scorching-hot summer morning, a team of five specialists arrived on the 17th-century Chigi family estate to inoculate more than six dozen trees within a deep forest that includes 2,000 pines.

Francesco Belli, whose father owns the gardening service deployed for the job, watched as a colleague drilled a ring of four-inch-deep holes around every tree’s trunk. Tiny plugs of nontoxic plastic were inserted in each to prevent fungal infections. Then Belli plunged a needle into the tree’s “veins” and began injecting a bug-killing serum.

“It’s drinking it all up quite nicely,” said Belli, sporting a straw cowboy hat to shelter himself from the sweltering sun.

The treatment poisons the parasites and, when not delivered too late, saves a tree from the vicious cycle they jump-start. In two to four weeks, the pine tortoise scale generally dies, though its target requires booster shots eight to 12 months later.

“If done properly, it all works quite well,” Audisio said.

The process costs about $116, on average, per pine. But the alternative is pretty gruesome for the trees, which are also contending with climate change.

“Pine trees are among those that resent [global] warming the most,” Blasi said. And those that are already weakened are more vulnerable to assault by the parasite — which in warmer temperatures can give birth to as many as five generations annually.

Several weeks ago, Italy’s Agriculture Ministry issued an emergency order to start treating pines, noting how public opinion has become “quite alarmed” by the threat to the trees.

“More can be done, we’re still waiting to find out how much money will be invested on this emergency,” said Marranghello, who in April organized a rally to pressure the ministry to act.

“This needs to be dealt with as one would with an earthquake.”

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