LOS ANGELES (Reuters) - California orange and lemon growers are bracing for a deadly bacterial disease that could ravage the state's $2 billion citrus industry after the first infected tree in the state was identified in a suburban Los Angeles yard.
The tree ailment, called Huanglongbing, citrus greening or yellow dragon disease, is usually spread by the Asian citrus psyllid, a tiny, aphid-like winged insect that feeds on the leaves of citrus trees.
The first appearance of the disease in California was confirmed on March 30 when a lemon-pomelo hybrid tree in Hacienda Heights, east of Los Angeles, tested positive. Experts believe it was transmitted by an infected bud shoot grafted onto the tree by a friendly neighbor and amateur horticulturist.
The disease poses no health risk to humans or animals, but its effect on citrus trees is lethal and without a known cure. The bacteria has previously devastated crops in China, Brazil and Florida.
The infection attacks the vascular system of the trees, causing a yellowing of leaves and death within a few years.
"This is the tip of the iceberg for California," said Ted Batkin, a former citrus grower and now president of the Citrus Research Board, which was responsible for detecting the diseased tree near Los Angeles.
"Never in our history have we dealt with a disease that is this persistent, and we have searched the world for 50 years and have not been able to find resistance to this bacteria," Batkin said.
The diseased tree in Hacienda Heights was removed, and officials are keeping a close watch on 400 to 500 other trees they suspect may have been infected, Batkin said.
State agricultural officials have set up a quarantine area of some 20,700 square miles (53,600 square km) to prevent potentially infected fruit from leaving a region that spans six California counties.
Growers are worried that if the disease spreads north it could wreak havoc on the prized orchards in California's Central Valley, the heart of the state's $2 billion citrus industry, causing significant losses in revenue and jobs.
California produces approximately 80 percent of the nation's fresh citrus fruit and is the country's main source of fresh-market oranges, according to the Citrus Research Board. The state also supplies 87 percent of the nation's lemons.
The Central Valley, a vast, fertile region stretching 500 miles from Bakersfield to Redding, accounts for the bulk of the state's overall citrus crop.
Also troubling is the potential toll the disease could take on the image of a region synonymous with sun and citrus.
"The disease could be devastating to our entire industry, economy, and our very identity," said Leslie Leavens-Crowe, a partner at Leavens Ranches in Santa Paula, California, a fourth-generation commercial grower of lemons and avocados. "We've complained about other pests, but this disease actually kills trees and there is no known cure."
The March 30 detection has sent growers racing to set up bug traps, hoping to stave off the advance of a deadly pathogen that already has cost billions of dollars in damage to citrus crops in Florida since 2005.
The pest and the disease have also turned up in Texas, Louisiana, Georgia and South Carolina. Arizona, Mississippi and Alabama have detected the pest, but not the disease.
The Citrus Research Board estimates that psyllids have invaded the Los Angeles basin by the millions since the bugs first arrived in the state in 2008, though not one has been found carrying the Huanglongbing bacteria.
The state and the industry have spent millions of dollars to curtail a potential outbreak of the disease, according to the California Department of Food and Agriculture.
Tens of thousands of bug traps have been set up around the state, and more than 10,000 psyllids have been tested so far, Batkin said. The remnants of one specimen turned up in a Central Valley trap, but the region appears so far to be otherwise free of the bugs. Some of the highest concentrations have been found in Echo Park, a Los Angeles neighborhood near Dodger Stadium, and stretching eastward into the nearby San Gabriel Valley.
Growers are taking special precautions in the Central Valley by setting up a grid system of traps, designed to mimic the appearance of citrus fruit, in commercial production areas.
"Our objective is to control the movements of the disease while researchers look for a way to cure it," state Food and Agriculture Department spokesman Steve Lyle said. "And it's not just commercial growers who have something at stake. It's residential growers, too."
The state estimates that 50 to 70 percent of residential properties in California have citrus trees.
Scientists are working on an early detection method that could be ready by the end of the year, according to the Citrus Research Board.
How far the disease might ultimately spread in California is unknown, but the psyllid can fly up to about 1,100 yards a day. "It's a funny little critter that may spend its entire lifetime on one tree, or it may search for one after the other," Batkin said.
Editing by Steve Gorman, Cynthia Johnston and Will Dunham