In Italy, trees are under attack from a tiny, round, reddish-brown invader. The pine tortoise scale latches on to its victim, excretes copious amounts of sugary liquid and waits for black sooty mold to take over. The nonnative pest from the Americas first showed up here in 2014, and it's threatening to decimate Rome's 1 million umbrella pine trees. Angelo van Schaik tells us how they can be saved.