Microsoft has an insect infestation to thank for its classic Windows XP desktop background—an image that has graced at least a billion computer screens since the system’s 2001 launch.

Napa Valley spent most of the 1990s trying desperately to curb the spread of phylloxera, a microscopic pest that was devastating its grapes. By the time the epidemic had run its course in 1999, some 50,000 acres of fields had been decimated.

Although the cost for growers was astronomical—half a billion dollars in total—the landscape of Northern California had never looked more idyllic. Endless rows of grapevines had been replaced by a lush carpet of grass, dotted here and there with...READ MORE