Shawn Mehlenbacher arrives at OSU to find the Oregon hazelnut industry defenseless against eastern filbert blight.
In the fall of 1986, plant breeder Shawn Mehlenbacher arrived at Oregon State University. One month later came the first reports of eastern filbert blight in a Willamette Valley orchard. The two events seemed fated.
What would have happened if Mehlenbacher had turned down the job? EFB, a fungus that can wipe out an orchard, had been devasting trees on the East Coast for almost a century. Oregon could easily follow suit.
How bad could it be? Trees would be dying by the thousands, leaving the Willamette Valley’s $91-million industry in ruins. Growers would struggle to stay in business. Many wouldn’t make it. One of the state’s lucrative crops could potentially be a thing of the past.
Many people thought the fungus would never jump the Columbia River from southwest Washington, where the first infected trees on the West Coast were found in an orchard in 1968. But it did. And in the mid-1970s, the disease took hold of the moderately susceptible ‘Barcelona’ variety of trees in an orchard near Damascus at the northern end of the Willamette Valley. It quickly spread.
When Mehlenbacher reached Oregon, farmers were desperate for help as they watched the disease’s bullet-hole cankers take over their trees. He collaborated with his predecessor, Maxine Thompson, walking through orchards, going tree to tree as he sponged up the knowledge she’d built over 17 years as the hazelnut breeder at OSU. Mehlenbacher began keeping his own meticulous records in an 8-by-14-inch green ledger. He still does. It’s easier, he says, than using a computer.
Thompson focused on breeding trees with better traits — better nuts, earlier harvest, vigor, thickness of shell, and growth habit — but switched her attention to eastern filbert blight when she found an unaffected tree surrounded by disease-ridden pollinizer trees in an orchard in southwest Washington. That discovery was named ‘Gasaway’ and provided the resistant gene for many of Mehlenbacher’s disease-resistant releases.
Hazelnuts — or filberts as they’re often called — thrive in the mild Mediterranean climate of the Willamette Valley. The nuts grow so well, Oregon rates No. 1 in production for the country with 99 percent of the crop, and No. 3 in the world behind Turkey and Italy. Undermining that success is eastern filbert blight (Anisogramma anomala), a fungal disease native to the eastern United States.
It’s not so much the hazelnuts but the genetic diversity in plants that fascinates me… It’s exciting. Besides, they’re healthy and make everything taste better.
The blight takes its time killing a tree — seven to 10 discouraging years when the cankers spread and leaves begin to turn brown, a sure sign of infection. Through management practices like pruning and judicious spraying, growers can mitigate the disease for a while but not stop it. The eastern filbert blight fungus releases a sticky, white ooze during wet weather. As wind spreads the spores, they settle on young shoots and penetrate cells where infection occurs. Eventually, cankers (or stroma) appear and start to girdle branches, which die back as the cankers expand.
Mehlenbacher, who was raised on a farm in western New York, came to Oregon from Rutgers University, where he was working with peaches, apples, and apricots. He quickly started with hazelnuts (Corylus avellana), a passion that’s persisted for 33 years. No, he says, he’s not bored with hazelnuts.
“It’s not so much the hazelnuts but the genetic diversity in plants that fascinates me,” he says. “I’m lucky to have a job I love that doesn’t feel like a job. I get to work in the field, in the lab, in the greenhouse; I get to teach and review manuscripts. There’s always something new. It’s exciting. Besides, they’re healthy and make everything taste better.”
That may be, but plant breeders, especially tree breeders, must be patient. It takes 17 years from the time two parent trees are crossed to the release of the best new variety. Every year, Mehlenbacher and his students and research assistants plant about 5,000 seedlings. Almost all the resulting trees will fall to the chainsaw.
At harvest time in September and October, Mehlenbacher grabs his ledger and heads to the OSU test orchard. Often, he can be found sitting on a stool with 60 acres of hazelnut trees spread out behind him at the research farm in Corvallis. Wearing his usual knit cap and plaid shirt, he scoops up nuts and separates each one from its husk. For days, he and his crew walk row by row, tree by tree, taking notes on crop load, nut shape and size, and other characteristics. Then they’re transported to the Nut House, an affectionately named field lab where the nuts are dried, counted, cracked by hand, and evaluated again — 7.2 million total in Mehlenbacher’s three-decade career. If the trees don’t come up to snuff, they’re out, he says.
“They get a D for discard,” he says. “If they’re good, we’ll keep the tree. We don’t keep many, though.”
One of the first to show promise was ‘Jefferson’, an offspring of ‘Gasaway’. Mehlenbacher and his group collected pollen, made crosses by hand, and came up with 144 promising seedlings. They released ‘Santiam’ and ‘Yamhill’, which were moderately resistant. But it was ‘Jefferson’ that really made a difference. It came to market in 2009, and since then it’s become the standard for the in-shell market that demands big, easy-to-crack nuts. Growers took to it immediately and began replacing ‘Barcelona’ orchards with the EFB-resistant variety.
Eventually, though, the disease will defeat the resistance bred into trees like ‘Jefferson’.
“It’s an ongoing battle,” Mehlenbacher said. “We’re OK for a while, but the fungus will eventually change and be able to overcome resistance. Two years ago, it was found that ‘Gasaway’ is no longer resistant back east.”