Jim Lerew knew three years ago something was wrong with the peaches in his orchard, but he couldn’t put his finger on exactly what it was. He went through the usual suspects: disease, nutrient problems, an invasion of western flower thrips. He took fruit samples to Penn State’s Fruit Research and Extension Center labs for extensive tests. No one seemed to know what was making his peach and nectarine crop look bad. Finally, at the end of the 1999 growing season, Lerew brought some samples to a fruit growers meeting at Rutgers University on the off chance someone might have some answers. A peach scientist who had studied in Europe helped Lerew find out what he was dealing with: plum pox virus.

Telling a fruit grower plum pox virus is present in a crop is roughly equivalent to punching someone in the stomach when he’s not looking. A devastating disease that affects stone fruit—peaches, nectarines, apricots, plums, and almonds—plum pox has infected more than 100 million trees in Europe, crippling fruit production in some regions, and is widespread throughout Chile, another major fruit-producing nation. It had never been seen in North America prior to Lerew’s discovery.