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Wasp fights citrus pests

The Los Angeles Times

LOS ANGELES — Pesticides haven’t worked. Quarantines have been useless. Now California citrus farmers have hired an assassin to knock off the intruder threatening their orchards.

The killer-for-hire is the tamarixia radiata, a tiny parasitic wasp imported from Pakistan.

Its mission: rub out the Asian citrus psyllid, which has helped spread a disease that turns citrus fruit lumpy and bitter before destroying the trees.

The pest is wreaking havoc in Florida’s 32 citrus-growing counties. In California, it’s been detected in nine counties, most of them south of the commercial growing areas in the Central Valley. Farmers are hoping the tamarixia can help keep it that way.

The wasp, which flew coach in a carry-on bag all the way from the Punjab region, is a parasite half the size of a chocolate sprinkle. But it kills psyllids like a horror movie monster, drinking their blood like a vampire. The female wasp can lay an egg in the psyllid’s belly. When it hatches, it devours its host.

The wasp “is going to be our number one weapon to control to Asian citrus psyllid,” said Mark Hoddle, an invasive species expert from the University of California, Riverside, who, over several trips, brought legions of wasps to California.

“We have no other choice except to use this natural enemy or do nothing. And the ‘do nothing’ option is unacceptable.”

So far, Hoddle and his teams have released more than 75,000 wasps across the Southland to beat back the disease, known as Huanglongbing or citrus greening. The malady was first detected in California last November, in a backyard citrus tree in Hacienda Heights.

The disease can lie dormant for a few years before tests are able to detect it, so experts suspect other trees are already infected.

“We’re looking for a needle in the haystack before it sticks us,” said Joel Nelsen, president of the California Citrus Mutual, a trade group.

The Department of Agriculture has enacted quarantines in nine states, including Florida, Texas and California. The quarantines prohibit interstate movement of citrus trees, and require labeling of citrus nursery stocks from areas where greening has been detected.

In California, the quarantine covers nine counties. That recent discovery raises the fear that the pest is creeping into prime citrus growing areas. It could threaten California’s $2 billion industry, which accounts for about 80 percent of the fresh market citrus production.

Since 2010, California growers have spent about $15 million a year to fight the psyllid. Much of that money goes toward detection and awareness efforts. That’s on top of millions the federal government and state Department of Food and Agriculture have kicked in.

The psyllids don’t kill citrus trees. They’re merely the agent that spreads Huanglongbing. An infected psyllid acts much like a dirty syringe flying from tree to tree, feeding and depositing a bacterium each time it unfurls its stinger.

Whether the killer wasp can bring the psyllid to heel remains to be seen. Florida growers imported a strain of the wasp from Vietnam, but it proved ineffective. The predator never took hold, partly because there was not enough genetic diversity needed to establish a population, researchers said.


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