Original post in Capital Press
While forecasters are predicting a record-high Oregon hazelnut crop in 2018, a newly published study suggests the industry might not be where it is today if growers did not use fungicides to manage a cankerous plant disease known as Eastern Filbert Blight.
The disease was first discovered north of Vancouver, Wash., in 1970, and by 1998 it had spread to the Mid-Willamette Valley where 99 percent of all U.S. commercial hazelnuts are grown.
Once a tree is infected with Eastern Filbert Blight, the disease can only be removed by pruning. Fungicides are also recommended to protect healthy plant tissue, though at the time growers wondered whether it made economic sense to spray mature orchards versus pruning alone.
Researchers at Oregon State University launched a 12-year trial from 2004 to 2015 to determine whether the annual cost of spraying fungicides was worth the financial return through sustained hazelnut production. The answer, they found, was a resounding yes.
“Fungicide use in hazelnuts not only limited (Eastern Filbert Blight) development but also protected future yield loss and gross financial returns,” the study concluded, adding that growers who spray fungicides annually should be able to recoup those costs after just a few years of finding the disease in their orchards.
Eastern Filbert Blight is a fungal disease in hazelnut trees that causes cankers in infected branches, where spores grow and are dispersed by rain. Trees usually decline in productivity slowly at first, then rapidly after 5 to 10 years.
Jay Pscheidt, a professor with the OSU Department of Botany and Plant Pathology and lead author on the study, said fungicides will not stop the disease, but does slow down its development. That is especially important as growers make the transition from susceptible hazelnut cultivars to newer varieties that are more disease-resistant, but need time to mature.
“It is the bridge between our susceptible cultivars and our resistant cultivars,” Pscheidt said.
Though hazelnut growers have planted nearly 40,000 acres of resistant trees, Pscheidt said about 30,000 acres of the old, susceptible orchards are still producing nuts, and the industry needs to maintain them until the younger blocks have a chance to grow up.
“We’re doing that with fungicides,” he said.
The OSU study was conducted at a 1-acre trial orchard at the university’s experimental field in Corvallis. Past research was limited to younger trees, Pscheidt said, and growers were eager to find out if fungicides could be effective in larger, more mature orchards.
“All of our research results were mostly on these little trees that we could cover really well,” Pscheidt said. “But it’s not like a mature orchard that’s 20 feet up, and you’re using an air blast sprayer.”
Researchers divided the orchard into 12 blocks of nine trees — eight Ennis trees, susceptible to Eastern Filbert Blight, and one Butler tree — giving each block three different treatments both with and without fungicides. Over the 12-year period from 2004 to 2015, total gross returns for non-treated trees were $30,150 per acre, while returns on trees treated with fungicide ranged between $33,804 and $35,972 per acre.
That means growers stand to make up to $4,274 more per acre more using fungicides to combat Eastern Filbert Blight than by simply pruning. More importantly, without fungicides, Pscheidt said mature hazelnut orchards may have died off faster than breeders can come up with new disease-resistant varieties, which may have stalled or even crippled the industry.
“If we didn’t have fungicides, we may not have had an industry,” Pscheidt said. “We still would have come up with resistant cultivars, but it would have been a real hard time between then and now.”