Threat to California Citrus May Finish Backyard Trees
New York Times – April 17, 2012
ALTADENA, Calif. — Like so many residents here, Martin Koning-Bastiaan grows citrus in his yard: lemons and limes, almost a dozen varieties of oranges, and grapefruit trees that are about 100 years old.
Citrus is an iconic part of California life. By some estimates, up to 70 percent of homeowners in the state 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.
But 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 last decade.
“We’re looking at the death knell of all the citrus,” Mr. 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 causes the disease clogs 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 $1 billion.
So California’s $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 last several years, California citrus farmers have poured $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,” Mr. 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, Calif., said it was important to test even healthy-looking trees for citrus greening. Because the disease kills very slowly, infected trees can live for several years before showing symptoms. But during that time, psyllids feed on the tree and spread infection.
“It’s very realistic that we can contain the spread, as soon as we can find the infected trees,” Mr. Batkin said. “If a tree is infected, it will then act as the Typhoid Mary, the reservoir to infect other trees.”
Other experts, however, are not optimistic that they can keep citrus greening out of California for long. “One thing we know about the disease, historically, is that it follows the pest,” said Mr. Lyle, of the California Department of Food and Agriculture. “As long as we have psyllids spreading a disease for which there is no cure, that’s a recipe for trouble.”
Still, even if greening disease does take hold in Southern California, researchers remain confident that the commercial citrus industry here can survive. Florida, despite having lost about a tenth of its citrus acreage since 2005, remains the largest producer of citrus in the country. Pesticide sprays have allowed farmers to combat the psyllids, while nutrient treatments have helped trees continue to produce fruit after they are infected.
For home citrus growers, though, the prognosis is bleaker.
When citrus greening disease arrives in a region, residential trees are usually the first to go, because they rarely use the pesticides that are most effective at keeping away psyllids, according to Mark Hoddle, director of invasive species research at the University of California, Riverside.
“Homeowners are probably going to lose their trees, because they won’t be in a position to spray them constantly,” Dr. Hoddle said. Many might plant new trees, but he warned: “There won’t be big trees people are proud of and have been around for 30 years since your grandfather planted it. Those types of stories will probably be a thing of the past.”
Commercial farmers have been preparing to deal with the disease, but most home citrus growers still know very little about citrus greening. Some inside the quarantine zone, who are not supposed to allow fruit to leave their property, continued to give their excess lemons and oranges to neighbors, unsure of what was permitted.
For devoted backyard growers like Mr. Koning-Bastiaan, though, the prospect of losing their trees is potentially devastating. “California is one of the best places in the world to grow citrus fruit,” he said. “But you see the writing on the wall. It’s really sad.”