March 2022 - 23

Affordable testing to fight little cherry disease set
By Scott Weybright
Washington State University
Washington State University will help
Washington cherry growers test more
trees for the damaging little cherry
disease thanks to a Washington State
Department of Agriculture (WSDA)
Specialty Crop Block Grant received
by the Washington State Tree Fruit
Association (WSTFA).
Named for its most distinct
symptom - small, colorless fruit -
what growers call " little cherry " is a
simultaneous outbreak of little cherry
virus-2 and the X-disease phytoplasma,
both of which produce similar symptoms
on infected cherry trees and are difficult
to tell apart, even by experts. This is more
difficult because symptoms are usually
noticed only a few weeks before harvest.
The pathogens are spread in
orchards by small insects: the virus by
mealybugs, and the phytoplasma by
leafhoppers.
Tests are available for growers to
learn if a tree is infected, but they can
be expensive. The new three-year,
$530,000 grant will help to expand
testing capacity at WSU's Plant Disease
Diagnostic Lab in Pullman with
more equipment and supplies. This
support will reduce testing fees by
approximately 50%, to $50 per test.
" Affordable and available testing
is a key element of our industry's
response to little cherry disease, "
said Jon DeVaney, WSTFA president.
" Washington's cherry growers
appreciate the support of the WSDA
Specialty Crop Block Grant Program
and WSU's Plant Disease Diagnostic
Lab in this effort. "
" Active, aggressive tree removal is
the best way to suppress this outbreak
and prevent further spread, and testing
is an essential tool to identify trees in
the early stages of infection, " said Scott
Harper, WSU virologist and director
of the Clean Plant Center Northwest.
" It will help growers make informed
management decisions for their
orchards. "
" Affordable and available
testing is a key element of
our industry's response to
little cherry disease. "
− Jon DeVaney, WSTFA
Harper's lab supported the initial
wave of testing in 2018-2019, and
commercial labs took over testing in
2020, but few growers could afford to
test every tree that they suspected might
be infected.
" WSU and collaborating laboratories
are working hard to provide growers
with little cherry testing services, "
said Tianna DuPont, a WSU Tree
Fruit Extension specialist. " Additional
support for the WSU plant diagnostic
lab is essential to provide sustainable,
Growers rely on the annual Buyers' Guide to
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Your
year-round,
24/7 resource
robust, public diagnostics so growers can
identify and quickly manage the multiple
problems that attack their trees. "
Removing infected trees quickly is the
best way to fight the disease, as there
is no treatment and early removal can
limit spread of the virus to nearby trees
in an orchard, Harper said. Testing also
helps avoid removing a tree exhibiting
symptoms that look like the disease, but
isn't infected with little cherry pathogens.
WSU tree fruit scientists work
closely with growers to fight diseases
and support the Washington cherry
industry, which produces more sweet
cherries than any other state. FGN
Cherry trees infected with little cherry disease bear small, bitter or bland fruits that often
lack attractive coloring. Photo: Washington State University
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