On a warm, blustery December afternoon outside the De Laurentis olive oil-producing co-op in the white hilltop town of Ostuni, Puglia, Luigi D'Amico holds out his palm, revealing an olive picked earlier in the day. Instead of resembling the plump, gleaming green and black fruit overflowing in bins around him, this one is half-consumed, dry and shrunken.

"That's what the olive fly does," he explained. "It lays its larvae, which then devours the olive." D'Amico lists off other pests and fungi — olive leprosy, peacock's eye fungus, the Margaronia moth — all spreading, he says, with the aid of the warm scirocco wind that didn't use to blow here in December, but with climate change, now does. "We need cold weather to kill off pests," he said. "And temperatures are rising."