Disease threatens citrus industry

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 neighbour 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 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 per cent 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 per cent of the nation's lemons. The Central Valley, a vast, fertile region stretching 800 km 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.