March 2022 - 15

WSU lab to study evolving tree fruit bacteria
By Seth Truscott
Washington State University
Joining Washington State University
(WSU) in February as the newly
established Endowed Chair in
Bacterial Diseases of Tree Fruits,
Frank Zhao will study and seek better
ways to manage devastating bacterial
pathogens in tree fruit.
In bad years, these microbial disease
heavy hitters such as fire blight and
X-disease phytoplasma cost apple,
cherry and pear growers hundreds of
millions of dollars nationally in lost
fruit as well as treatment and removal
of infected trees.
" We need more tools in our toolbox
to deal with bacterial diseases,
particularly for organic orchards, " said
Zhao, who comes to WSU from the
University of Illinois to launch a new,
industry-funded research program in
tree fruit microbiology.
Growers' most effective tool has
always been antibiotics - chemical
drugs that kill bacteria or make it
difficult for them to reproduce.
But bacteria can develop resistance
that renders antibiotics less or even
totally ineffective. In organic orchards,
chemicals are often prohibited, raising
demand for new techniques.
" Disease outbreaks can be
unpredictable in their severity, " Zhao
said. " Pathogens change over time -
we now know there are at least four
different strains of the fire blight
pathogen. "
Becoming interested in plantpathogenic
bacteria as a master's
student in China, he has spent his
career studying where pathogens
come from and how they adapt and
survive, most recently the fire blight
bacterium, Erwinia amylovora, which
has caused serious damage in Pacific
Northwest orchards in the past several
years, as well as the pseudomonas
family of bacteria, which infect a
range of crops.
Zhao studies both good and
bad microorganisms. Devising
strategies to control harmful bacteria
with beneficial microbes, he has
experimented with nanoparticles as a
method to deliver biocontrol agents
in orchards. He plans to continue
studies of biocontrols and " good "
microorganisms at WSU.
Working in the field and the
lab, Zhao will screen for and map
antibiotic resistance in Washington
orchards, identifying the predominant
strains of top-priority pathogens such
as fire blight and bacterial canker of
sweet cherries.
As he begins his efforts in
Washington, Zhao will connect
with growers to understand their
experiences and challenges.
" All these will help me
tremendously in getting my program
started, " he said. " In turn, I can learn
from them and better solve the disease
challenges that fruit producers are
facing. " FGN
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or call (800) 876-2767
FGN | MARCH 2022 | 15
Frank Zhao. Photo: Washington State University
X-disease phytoplasma is a costly disease for apple, cherry and pear growers.
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March 2022

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