Not long after Mark Boyer planted the apple orchard he co-owns in Schellsburg, Pennsylvania, the trees started to die. First, their leaves turned yellow. Then, their trunks shed bark. In two short weeks, they were completely dead. And once the physical signs started to appear, there was nothing Boyer could do to stop the progression. Whatever was killing his trees was already too far along.
Whatever it was, it had no particular season. It happened during the spring, as the trees blossomed, or later in the fall, when they were laden with fruit. Some trees even died after the final harvest, just before winter set in.
To make matters worse, there was no discernible pattern. Five healthy trees could surround a single dead one, suggesting that the problem wasn’t spreading through leaves or soil. Boyer first spotted trouble in 2011. By 2013, it was much worse.
Boyer investigated every possible cause. He tested his soil for heavy metals and nematodes. He checked his records to make sure he hadn’t misapplied weed killers. Nothing looked obviously wrong, but the trees continued to die.
He asked other growers if they were having similar problems. Many said they had lost trees, but they attributed the deaths to the stress of cold winters and other identifiable hazards like the contagious bacterial disease fire blight.
“I kept saying, ‘no, this is different. You know, this is really something different,’” Boyers says.
Around the same time, Kari Peter, a plant pathologist specializing in tree fruit, joined the faculty at Penn State University. She had noticed a few trees dying at random in her own orchard, but didn’t think too much of it—apple trees die all the time. It wasn’t until 2014 that a grower approached Peter with concerns about a mystery illness that was affecting young trees. By the latter half of the year, more and more growers had gotten in touch. “And then I heard from New York that they were seeing something similar, and also from North Carolina,” she says. Read more