In 1910, humans accidentally introduced a disease to American forests that’s killing whitebark pine and effectively creating “ghost forests” across the West. White pine blister rust is a fungus that swells into a canker, releasing resin and drawing in rodents in search of a carb-rich snack. Eventually, the stress is too much for the tree to handle. It dies, while the orange, powder-like disease flies on to infect more pines. But about one in every 100 trees seem to show genetic resistance to the disease. Forest managers hope to harness those resistant trees to save the species.