Over the past decade, Oregon's hazelnut acreage has more than tripled as growers replace older trees with newer disease-resistant varieties such as Jefferson, Wepster, and PollyO. These cultivars were developed by Oregon State University (OSU) to combat Eastern Filbert Blight, a fungal disease first introduced to the Pacific Northwest in the late 1950s.

"It was accidentally introduced somewhere in the Vancouver, Washington area, and it slowly started to move down the valley," said Nic Wiman, a hazelnut specialist and associate professor of horticulture at OSU. The disease was first confirmed in Oregon in 1986. OSU researchers began developing resistant varieties decades earlier, recognizing the need for long-term control.

"Our first hazelnut breeder started in the 1970s, but hazelnuts are a very long-lived crop, and so it literally takes about 17 years from the time when they make a cross to when they know if it's a variety worth releasing or not," said Wiman.

Since then, OSU has released multiple commercial hazelnut cultivars using a resistance gene that protects against the disease. However, Wiman said that recent mutations of Eastern Filbert Blight are now overcoming the single-gene resistance. "Just in the last couple of years, we've realized that the disease has mutated. We have new strains of the Eastern Filbert Blight that overcome the single gene resistance," he said.