For a crop that’s been grown in Oregon’s Willamette Valley for over a century, there’s still a lot to be learned about hazelnuts.
As hazelnut growers were preoccupied with defeating their mortal enemy — a fungal pathogen known as Eastern Filbert Blight — there wasn’t as much energy devoted to studying basic production.
“Everybody’s been chasing the Eastern Filbert Blight. We knew very little about the disease when it first came in,” said Nik Wiman, Oregon State University’s orchard specialist in Western Oregon.
Now that growers have developed ways to combat the pathogen and OSU has introduced several hazelnut cultivars resistant to the disease, Wiman can focus on the fundamentals: How to protect trees from insect invaders? What is the best mulch to use? How much water to apply?
“We’re trying to maximize growth,” he said.
While opinions on production methods are often based on anecdotes, Wiman is trying to develop recommendations grounded in data and science.
Much of OSU’s research on nutrients has grown outdated as farmers have replaced traditional varieties, such as Barcelona, with new ones that spring from other parts of the globe.
As it turns out, nutrient demands can vary significantly among cultivars. Growers also have more flexibility these days with fertilizers that are applied to leaves or through irrigation lines.
Traditionally, growers only fertilized during spring because it was thought hazelnuts didn’t take up nutrients in the summer. However, that’s only the case if they’re not irrigated.
Wiman is wrapping up a three-year study that aims to refine the timing of fertilizer applications and better understand their effects on tree and nut development.
The issue is complicated because the tree’s response to nutrients depends on the accumulation of heat over the season, so timing will vary from year to year.
“There is so much change, even in a small time frame like a month,” Wiman said.
Hazelnuts were historically grown as a dryland crop but the industry is increasingly turning to irrigation, especially to get young trees established.
Wiman has found that trees respond better to sprinklers than drip irrigation, since there’s better water penetration of the entire soil surface.
With drip irrigation, on the other hand, dry soil can pull water away from the tree’s root mass.
Even so, drip lines are likely to remain the standard in hazelnut orchards, simply because many farms don’t have access to ample irrigation water, Wiman said.
Over time, the industry will probably adopt automated irrigation controls that begin watering orchards as soon as soil moisture or tree sap sensors indicate it’s necessary, he said.
“We want to promote responsible water use,” he said.
Rows of hazelnut trees growing at Oregon State University’s North Willamette Research and Extension Center in Aurora receive varying amounts of irrigation, with Wiman and his researchers carefully measuring the effects on each tree.
It’s likely that releasing smaller amounts of water over time is more beneficial than irrigating all at once, since the water stays closer to the surface rather than seeping too deep for roots to absorb, he said.
As an entomologist, Wiman also spends time on the pests that afflict hazelnut orchards.
Flathead borers, for example, are especially drawn to young trees, which is a problem for Oregon’s burgeoning industry — more than half the acreage is non-bearing, he said.
Farmers who found the borers in their orchards brought branches to Wiman, who sealed them in wax to preserve moisture and observed their development.
Such observation yielded biological information about the insect that wasn’t previously available. It also turns out the borers have a natural enemy: a wasp that lays eggs into their larvae, killing them.
Encouraging such beneficial predators is a matter of judicious pesticide use to avoid killing off these “biological controls,” Wiman said.
That’s a tough task with brown marmorated stink bugs, a recently introduced pest from Asia that difficult to treat without broad-spectrum chemicals that also kill helpful insects.
“They can actually feed right through the shell and damage the kernel inside,” Wiman said.
Fortunately, another wasp species preys on stink bugs, which is how their population is limited in Asia. The insects are being bred at OSU’s research center in Aurora and released at infested sites.
“It showed up on its own. It followed its host,” Wiman said. “We think it’s going to have a huge effect long term.”
Wiman said it’s an exciting time to work as a hazelnut researcher, since the industry is experiencing “incredible growth.” He also appreciates the “culture of sharing” among hazelnut farmers.
“These growers feel like family almost,” Wiman said. “There’s a lot of innovation by the growers themselves.”
Occupation: Orchard specialist at Oregon State University
Hometown: Corvallis, Ore.
Family: Wife, Michel, and two daughters
Education: Bachelor’s degree in biology from Montana State University, Master’s degree in entomology from Montana State University, Doctorate in entomology from Washington State University.