Nuts to the Blight

Hazelnut trees at Third Knight Farms near Albany Jason E. Kaplan Hazelnut trees at Third Knight Farms near Albany

Researchers are fighting to save Oregon’s signature crop — but hazelnuts are not out of the woods yet.


The Columbus Day Storm that blew into Oregon in October 1962 still ranks as one of the most intense and deadliest in the country. Hazelnut grower Rich Birkemeier’s dad had just purchased his first farm in Canby. The storm toppled two-thirds of their trees. Luckily, they had harvested the nuts the previous week. Others weren’t so fortunate. It was a disaster.

Little did hazelnut growers know at the time, but a much bigger threat was already lurking in the limbs of trees still standing just north of Portland. An insidious fungal infection, known as eastern filbert blight, had already invaded orchards in Clark County, Washington, but scientists didn’t figure that out until decades later.

Soon, the outbreak jumped across the Columbia River and slowly spread down the Willamette Valley.

At one point, the relentless disease looked like it could wipe out the industry. No one knew how to stop it. The first infected Oregon orchards were quarantined. Feeling helpless against the fungal onslaught, some farmers wanted to bulldoze their neighbors’ diseased trees. But by the time any farmer spotted the telltale small black bumps dotting the branches, it was too late to stop the spread.



Yet, 30 years after the blight put Oregon’s signature crop in peril, hazelnut farming is booming. In fact, industry fortunes turned up as the national economy hit the skids in 2008 and have gained momentum in the past few years.

The 2018 Oregon hazelnut production ending in June is on track for a record-high 51,000 tons, a 60% increase from the previous year. In another record, the state’s hazelnut acreage has more than doubled in the past seven years to about 80,000, according to a December estimate from Oregon’s Hazelnut Marketing Board.

The new acres are planted with new varieties specially bred to resist the blight. As a result, nut production is expected to double by 2025.

Despite all the positive data, the hazelnut industry isn’t out of the woods yet. The blight continues to thrive. Slightly less than half of the state’s mature hazelnut acreage remains infected and contagious.



The new exuberance around hazelnuts is based on the premise that growers will be able to control infection in mature trees until they can be replaced, and that new trees will not be fatally infected. Neither is a sure thing.

“We are concerned the fungus could change, and our resistance gene will no longer be resistant,” says Shawn Mehlenbacher, who runs the hazelnut-breeding program at Oregon State University. “Or someone could bring infected material from the eastern states.”

It’s illegal to import hazelnut stock into Oregon, but researchers and farmers believe it’s just a matter of time. If that happens, the first wave of new varieties are sitting ducks. They know this because Mehlenbacher has sent the university’s new varieties to research collaborators at Rutgers University in New Jersey. Ominously, all succumbed to the multiple strains of eastern filbert blight endemic there.

JEK 4036Jimmy Lee of Third Knight Farms planted these hazelnut trees four years ago.  Photo: Jason E. Kaplan

So far, science seems to be winning the battle against the blight in Oregon. Research — and the money supporting it — came to the rescue once. The industry is banking on a repeat performance, should the valuable commodity face more virulent blight strains lurking on the other side of the Rocky Mountains.

Most of the scientific research to protect the hazelnut crop was funded by a kind of private tax Oregon growers assess on themselves every year to fulfill priorities. In 2014 they raised their self-tax to shore up the hard-won reprieve. Other crucial research support came from federal dollars and state funds.

The funding has helped build the world’s largest hazelnut-breeding program, located at Oregon State University and now bigger than all other such programs in the world. There, researchers began leveraging plant genetics to propagate new blight-resistant varieties. Meanwhile, pathology studies and field tests revealed how the disease spreads and how to manage blight-infected trees until they can be replaced.

Mehlenbacher credits the Human Genome Project with the more sophisticated genetic tools he and his students now have to create plants with multiple sources of defenses. The breeding process is no faster, but it’s more efficient. For example, instead of waiting for offspring of crosses to succumb to the blight, Mehlenbacher can track genetic markers to select the best prospects.

Meanwhile, the plant doctors had gotten busy, giving Mehlenbacher the time he needed to develop the new varieties. By 1990 or so, pathology researchers had discovered how and when the fungus was getting into plants. It wasn’t easy.

“It’s so difficult to spot in a tree,” Birkemeier says. “There’s an 18-month latent period. Then the little black pustules are only one-eighth of an inch. If you drive by in a tractor, you don’t notice. A branch dies. A twig acts as a flag that something is wrong. When you find it, it has been there three to five years or more.”



The blight spreads in rainy weather. The wet cankers on the branches spew spores. But the spores don’t actually infect the tree until spring, when tender, young green shoots appear. So researchers designed a way to control the blight while infected and susceptible trees remain: rigorous inspection and pruning of infected limbs in winter, and four fungicide applications in the spring.

Oregon State University has released 13 new crop varieties, each more resistant than the last, and a dozen pollinator varieties, as well as three ornamental hazelnuts for homeowners.

With the blight under control, resistant trees available and more secure resistance on the horizon, growing hazelnuts has begun to look like a good business decision again. Driving home the point, in 2014 Oregon hazelnuts sold for record prices, thanks to a freeze in Turkey, which shrunk their harvest. Turkey still dominates the market, supplying about 70% of the world’s hazelnuts, mostly in kernels to use in products ranging from Nutella to chocolates to oil.

Much of the land in Oregon considered ideal for hazelnuts has been taken. That hasn’t stopped farmers, especially in Benton and Linn counties, which have seen between a 500% and 800% increase in hazelnut acreage on land previously considered marginal.

About four years ago, Jimmy Lee, owner of Third Knight Farms, ran the numbers on hazelnuts — a long-term, high-value crop akin to wine grapes and blueberries — blight-resistant trees, mechanical harvesting, low labor costs and cheaper farmland in the southern valley. The only problem was the heavy clay soils. Hazelnut roots don’t like standing water.

JEK 4135The next generation of blight-resistant young hazelnut trees at Third Knight Farms near Albany

To improve the winter drainage in his new orchards near Albany, Lee dug rows of ditches and sunk perforated pipe in gravel 4 feet under the soil (known as tiling). Clay dries out in the summer, so he also dug wells and installed irrigation systems. At up to $2,000 an acre, tiling for hazelnuts is a good investment, he judged.

Lee, 39, now has more than 350 acres in hazelnuts near Albany. As a further safeguard, he planted two different varieties in each plot, or “double density,” to be able to choose the best ones when it comes time to thin half of them. “Hopefully,” Lee says, “my trees live longer than I do.”

The Oregon hazelnut industry remains vigilant. In March they held meetings and submitted comments to discourage a proposed rule change in Canada to cancel the restriction on importing hazelnut material from infected eastern provinces into British Columbia, whose hazelnut industry also was devastated by the blight.

“Right now, we’re in a really great place, but we can’t rest on our laurels,” says Oregon State University plant pathologist Jay Pscheidt. “Early on, people wanted to have vigilante chain saw parties. There’s still a lot of fungus out there. Now we can deal with it.”

DNA Defense

The resistance genes that saved the Oregon hazelnut industry came from trees that survived the original Clark County outbreak. Maxine Thompson, who with her colleagues created the university’s hazelnut-breeding program in 1969, first tried counting cankers to choose parent trees with the least symptoms, hoping some of the offspring would inherit the unknown “quantitative” resilience genes. Those genes are only now being tracked down to their specific locations on the 11 chromosomes of the hazelnut genome.

She also noticed that every third tree in a decimated orchard seemed to be spared. Those were pollinator trees of an obscure variety called Gasaway. This would become the Oregon hazelnut industry’s first great genetic hope.

She crossed Gasaway with other varieties and planted 300 of their offspring at the Washington State University experimental station in Vancouver. Some seedlings died, others became diseased and a few stayed clean. Thompson retired. Shawn Mehlenbacher, who runs the hazelnut-breeding program at Oregon State University, started in 1986. One month later, the blight was first detected in Damascus.

Mehlenbacher selected 13 of Thompson’s healthiest experimental plants to breed the first lines of defense against the Oregon invasion. He crossed the experimental mixes with other varieties. It takes 17 years to choose parents, make crosses, grow offspring, assess them and their nuts, and finally release them to farmers.

To increase his chances of success, Mehlenbacher began collecting diverse hazelnut genetic material around the world. He ordered samples by mail from Western Europe in the late 1980s, visited Turkey in 1993, and eventually made it to the hazelnut orchards of the former Soviet Union in Georgia and Azerbaijan.

In 1997 Mehlenbacher released “Lewis,” a variety with quantitative resistance and a lower canker count. It was a lifeline for dying orchards, but it required vigilant pruning and spraying. In 2005 Oregon State University released the first new variety carrying the Gasaway gene, followed three years later by “Yamhill,” a productive tree for kernels and widely planted. Many more varieties are in development and testing.

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