Thu, Apr 19, 2012 - Page 7 News List

Citrus greening disease threatens Californian trees

HERITAGE UNDER THREAT:Experts say there is little chance of stopping the blight, and that homeowners with a few cherished trees in their yards will be the first victims


Like so many residents here, Martin Koning-Bastiaan grows citrus in his yard: lemons and limes, almost a dozen varieties of oranges, and grapefruit from trees that are about 100 years old.

Citrus is an iconic part of California life. By some estimates, up to 70 percent of state homeowners have at least one citrus tree on their property. Up and down residential streets in this area northeast of Los Angeles, most homes boast an orange or lemon tree, the fruit so plentiful it spills over fences and onto the sidewalks.

However, all of these trees are now in danger.

Last month, state inspectors found a tree in a front yard just south of here infected with citrus greening, the world’s most devastating citrus disease, which has ravaged millions of trees as it has spread around the world from Asia in the past decade.

“We’re looking at the death knell of all the citrus,” Koning-Bastiaan said. “I’m not going to buy any more citrus until I know they are going to survive.”

Commercial farmers have begun spraying their crops with pesticides to ward off the insect that carries the disease, but some experts fear that citrus greening could all but wipe out residential urban citrus growth in areas like this one.

“This is part of California’s heritage, part of the California experience. People have citrus on their properties, and they feel passionately about it,” said Steve Lyle, a spokesman for the California Department of Food and Agriculture. “The risk to that is significant.”

Citrus greening originated more than a century ago in China, where it was called huanglongbing, or “yellow dragon disease.” The bacteria that cause the disease clog the flow of nutrients through the tree, turning the leaves yellow while the fruit remains green, lopsided, bitter and unusable. Infected trees die within about five years; there is no known cure.

The disease is transmitted by a small winged insect, the Asian citrus psyllid, and it can be disastrous for commercial citrus farmers. In Florida, where the disease arrived in 2005, it has cost the citrus industry more than US$1 billion.

So California’s US$2 billion citrus industry has dreaded the arrival of greening disease since 2008, when the psyllid first showed up in San Diego. The insect has since entrenched itself across Southern California.

Farmers like John Gless, whose family has grown citrus in the region for more than 100 years, fear the disease could ruin them. And over the past several years, California citrus farmers have poured US$50 million into detection and treatment programs, as well as efforts to find a cure.

“This is the biggest all-time threat we’ve ever had,” Gless said. “I’m the third generation, and I’ve got two more generations working .for me, but you look at Florida and think, we could be done.”

So far, state inspectors have found only one infected tree and a couple of infected psyllids, all in Hacienda Heights, east of Los Angeles. Citrus in that area is now under quarantine, and inspectors are testing nearby trees so they can remove any others that might have been infected.

Ted Batkin, president of the Citrus Research Board in Visalia, California, said it is important to test even healthy looking trees. Because the disease kills very slowly, infected trees can live for several years before showing any symptoms. However, during that time, psyllids feed on the tree and then spread the infection.

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