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Report of citrus greening disease in western Mexico worries California orange growers

The discovery shows that the tree-killing disease, which has ravaged groves in Florida and Brazil, is working its way toward California.

December 15, 2009|By Jerry Hirsch

California orange growers say they see ominous news in a report out of Mexico last week that agriculture officials discovered 51 trees infected with the feared citrus greening disease in the western Mexico coastal states of Nayarit and Jalisco.

The discovery shows that the tree-killing disease is working its way toward California's $1.6-billion citrus industry.

It has already ravaged the citrus industries in Florida, Brazil and other prime orange-growing regions and poses a major threat to California growers, according to agriculture officials.

What's especially worrisome is that the infected trees were discovered by visual inspection and symptoms such as irregular blotching on leaves were obvious.

Citrus trees can be infected for several years before displaying symptoms. And that means citrus greening could be more widespread, said Jim Cranney, president of the California Citrus Quality Council in Auburn.

"Having a discovery so far west and so close to California is very alarming," Cranney said. "This shows that the disease is spreading in Mexico and is getting closer to California."

The disease was already detected far to the east in the Yucatan, but these latest discoveries are only about 1,000 miles south of California, Cranney said.

California is already home to growing populations of the Asian citrus psyllid, a tiny aphid-like insect that is one of the two components that are destroying orchards in many of the world's prime orange- and lemon-growing regions.

By itself, the insect won't do damage to a citrus crop. However, when it becomes infected with citrus greening disease, also called Huanglongbing, or HLB, the bug becomes a carrier.

It flies from tree to tree, feeding on the plant and spreading the disease.

This is how citrus greening has destroyed tens of thousands of acres of Florida orange groves, and state and federal officials are worried that the scenario will be replayed in California, which produces almost all of the nation's fresh oranges and lemons.

There is no cure for the tree disease and no known way to prevent a tree from becoming infected once a tainted psyllid feeds on it.

Until now, the nearest outbreaks of citrus greening have been in Louisiana and Mexico's Yucatan Peninsula. But the psyllid is a pervasive pest in Mexico.

"You can see why we are talking about 'when' the disease gets here rather than 'if,' " said Beth Grafton-Cardwell, a UC Riverside entomologist based in the San Joaquin Valley.

Mexican agriculture officials are trying to knock down the region's psyllid population by removing the trees and spraying pesticides in the area of detection. But, she said, the disease may already have spread to other regions in Mexico.

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