California passes Florida in citrus production

• Florida’s industry devastated by disease

• Florida produced twice as much citrus as California as
recently as 2012

For the first time in 70 years, California has surpassed Florida
in citrus production, according to the University of California,
Davis.
Florida groves have been decimated by a disease called
huanglongbing (HLB), or citrus greening disease, that threatens
citrus production in California, too.
“HLB is not just bad for farmers and the economy,” says Carolyn
Slupsky, a biochemist and nutritionist with the University of
California, Davis. “The loss of fresh oranges and other citrus is
a real possibility and that would seriously impact our health.”
Ms. Slupsky and other UC Davis experts are working with
farmers and fellow scientists to develop early detection
methods, boost tree immunity and find a cure for the
devastating disease.
California farmers sold nearly 4 million tons of citrus in the
2016-2017 marketing season, compared to 3.5 million tons from
Florida, according to the U.S. Department of Agriculture. Florida
produced twice as much citrus as California as recently as the
2011-2012 season.
Florida didn’t lose its top spot because the Golden State is
producing more citrus. In fact, California farmers produced 14
percent fewer fresh oranges this season.
Citrus greening disease is caused by a bacterium that is spread
by the Asian citrus psyllid, a tiny insect that feeds on the leaves
and stems of citrus trees. A tree infected with HLB can live for
years without symptoms, allowing the pathogen to spread
undetected to other trees. Symptoms emerge over time as a
tree’s fruit starts to turn green and misshapen with a bitter,
metallic taste.
HLB is a global threat. Beyond Florida, the disease has
destroyed groves in Asia, Brazil and the Dominican Republic.
The disease has been spotted in about 250 backyard trees in
Southern California, but so far California’s commercial orchards
— many of which are in the Central Valley — have been spared.
Researchers are hard at work to keep it that way. An
international team of scientists led by UC Davis chemical
ecology expert Walter Leal recently identified the molecule that
attracts the Asian citrus psyllid, which may help researchers
develop a less toxic way to trap the insect to slow the disease’s
spread.
Ms. Slupsky is taking a different tack. She and her team are
using nuclear magnetic resonance technology to study how the
pathogen affects the metabolism of the tree. Her research
shines a light on HLB’s mode of attack.
“The pathogen seems to cause havoc with a tree’s ability to
defend itself from infection,” Ms. Slupsky says. “That’s a
spectacular discovery, because when we understand the
mechanisms behind the attack we have a chance at blocking
them and boosting a tree’s natural immunity.”
Working with Kris Godfrey, an associate project scientist at the
UC Davis Contained Research Facility, and Michelle Heck at
Cornell University, Ms. Slupsky found differences in the
chemical fingerprint of leaves starting very early in the infection
process. With further research, she believes that she can
develop a chemical profile to provide a reliable, rapid and early
indicator of the presence of infection.
“Early detection is key,” Ms. Slupsky says. “If we can catch the
disease early in the infection and get rid of the infected trees,
we can hopefully slow down the spread of HLB enough to give
scientists time to find a cure.”
Breeders are working to develop HLB-resistant rootstock, which
is one of the most promising avenues to a cure. Researchers
are also looking at whether they can transform the psyllid to
prevent its ability to spread HLB. UC Davis plant pathologist
Bryce Falk is leading a search to find and engineer viruses that
can induce traits in the insect that prevent it from transmitting
the bacterium.
Breeding rootstock and engineering viruses takes time. In the
meantime, backyard citrus growers can help keep HLB at bay
by monitoring their trees for signs of psyllids or infection and
removing trees that are infected or near infected trees.
Ms. Slupsky says that together, farmers, gardeners and science
can help save citrus and the nourishment it provides.
“From a nutritional standpoint, it’s hard to beat fresh citrus,” she
says. “Oranges provide energy, fiber and a wide variety of
nutrients, vitamins and minerals. They’re one of the most
consumed fruits in the United States. I can’t imagine life without
fresh citrus.”

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