Pressure’s on to combat insect battering U.S. citrus crops

A dead orange tree stands at the beginning of a grove Dec. 11 in Plant City, Fla. Citrus growers are worried about citrus greening, a condition where an insect causes bacteria to grow on the leaf and fruit, eventually killing the tree. (Associated Press)
A dead orange tree stands at the beginning of a grove Dec. 11 in Plant City, Fla. Citrus growers are worried about citrus greening, a condition where an insect causes bacteria to grow on the leaf and fruit, eventually killing the tree. (Associated Press)

In a secure Biosafety 3 containment facility at the University of California, Davis, researchers are required to disrobe, pull on scrubs and pass through negative-pressure doors – something like an airlock – before they can begin their work. Leaving requires a shower and more airlocks.

“Everything is completely contained,” said MaryLou Polek, whose organization helps fund some of the research done at the facility. “They can’t even take a notebook out. They have to email their results out.”

Biological weapons? Well, in a way.

The building is called the UC Davis Research Containment Facility. And in this state-of-the-art operation, researchers work with exotic pests and pathogens that threaten U.S. agriculture and natural resources, things such as the glassy-winged sharpshooter and the brown marmorated stink bug.

They’re also studying what may be the biggest threat these days to the U.S. citrus industry: the Asian citrus psyllid.

An insect that’s no bigger than the head of a pin, the Asian citrus psyllid is responsible for spreading a disease called citrus greening that is wreaking havoc on citrus growers.

Growers in Florida have been grappling with it for years, and government officials recently stepped up their efforts to combat it. And growers in California – another huge producer of citrus crops – are on edge, as the insect and the disease have appeared in the state but not yet caused widespread problems. In labs on both ends of the country, researchers are employing different strategies to detect the disease, stop its spread, and hopefully cure already-sick trees.

“Florida is concerned about therapeutics; their industry is already so highly affected,” said Polek, vice president of science and technology for the Citrus Research Board, based in Visalia, Calif. “If they don’t find a way to cure their plants, they’re sunk. In California, we’re trying to not get to that point.”

Citrus greening is also known as Huanglongbing, or sometimes yellow dragon disease, and it first appeared in Asia during the late 1800s. It has decimated citrus crops in Asia, Africa, the Arabian Peninsula and Brazil.

The insect that spreads the disease – that pinhead-size Asian citrus psyllid – was first seen in Florida in 1998. The disease itself appeared in Florida in 2005 and rapidly spread to all 32 citrus-growing counties.

The disease migrates when infected plants are moved and come into contact with the carrier insect, which can transmit it to other trees.

The bacterial disease is not a threat to humans or animals, but takes hold in a tree and eventually causes it to produce green, bitter-tasting fruit, ruining crops meant for sale to consumers or juice-makers.

Krysta Harden, deputy secretary of the U.S. Department of Agriculture, recently toured citrus groves near Tampa, Fla.

“A healthy orange makes you want a glass of juice,” she said. “And then to see this hard, small green fruit is devastating.”

Prakash K. Hebbar, national coordinator for the USDA’s citrus health response program, said that while it took five or six years for the damage to really be seen, it’s now showing up in reduced yields and lower quality of fruit. Much of the recent reduction in citrus production is because of the disease.

U.S. Rep. Vern Buchanan, a Republican from Sarasota, Fla., said growers in his state are suffering from their smallest orange crop harvest in 24 years. He pushed for citrus-greening funds in both the omnibus budget bill passed by Congress in January and the farm bill passed by Congress this week.

The farm bill contains $125 million in mandatory funding for citrus-greening research and $125 million in discretionary funding for the disease.

Buchanan, from his walks through orange groves in recent years, described fruit “that just looks like it’s dying.”

“It’s turning colors, doesn’t have its natural state, is usually one-third the size of normal,” he said. “Some trees look like they’re going to be dead in a year or two.”

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