September 2020 - 13

OSU Extension card helps cherry growers spot X disease
By Chris Branam
Oregon State University
X disease has become a serious
problem in the cherry growing regions of
Oregon and Washington, causing growers
to remove hundreds of valuable trees
from their orchards.
Also known as little cherry disease,
X disease was first identified in Oregon
in 2017. X disease decimated the cherry
industry in California twice - in the 1940s
and 1990s.
This year, Oregon State University
(OSU) Extension came prepared to help
growers spot the dreaded disease prior to
and during this year's harvest that began
in June.
In March, OSU Extension created
a card that field workers could use to
identify X disease in orchards. One side
of the card is in English and the other side
is in Spanish. The card describes disease
symptoms, includes a photo of affected
fruit, and features a QR code that leads to
the X disease entry in Pacific Northwest
plant disease handbook.
Cherry virus and virus-like
problems are common in orchards
throughout Oregon, and range from
the mostly benign to lethal. The most
serious viruses, such as X disease, spread
quickly throughout a growing
region, significantly reducing fruit quality
and yield.
Controlling these diseases is vital to
the health of Oregon's cherry industry. X
disease is incurable and will spread
rapidly, so the primary method to control
it is cutting down symptomatic trees
as soon as possible, preferably during
the growing season.
Ashley Thompson, an assistant professor
of horticulture and fruit tree Extension
specialist in
Hood River and
Wasco counties,
said growers
had become so
cautious about
X disease, they
were cutting
down trees that
might not have
ASHLEY
THOMPSON
been affected.
" Identifying
cherry
viruses based
on symptoms can be confusing, "
Thompson said. " For example,
X disease can be confused with small
cherries, which are small but ripen
normally. We don't want our cherry growers
to remove trees if they don't have to. "
X disease symptoms are little, pale-red
to greenish-white fruit that do not taste
ripe. Some cherries might be pointed
or flat-sided. These cherries will not
ripen. Normal-looking fruit on a
branch with unripe fruit will have poor
flavor. Symptoms are most noticeable two
weeks before harvest and through harvest
when normal looking fruit is mature.
Since she came to OSU in the spring
of 2018, Thompson has been working
alongside OSU colleagues Jay Pscheidt, a
professor of botany and Extension plant
FGN | SEPTEMBER 2020 | 13
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pathologist, and doctoral candidate Lauri
Reinhold, to help cherry orchardists
mitigate the spread of X disease in the
Columbia Gorge.
In 2019, Thompson identified 52
trees infected in Wasco County and
provided growers with bilingual flyers
describing X disease symptoms. She also
highlighted X disease and other serious
cherry viruses at Extension's annual
cherry pre-harvest tour in The Dalles.
She is a member of the Little Cherry
Virus Task Force, an initiative of
Washington State University and the
Washington State Tree Fruit Research
Commission. FGN
X disease symptoms are little, pale-red to greenish-white fruit that do not taste ripe.
Some cherries might be pointed or flat-sided. Photo: Ashley Thompson
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September 2020

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