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Citrus greening cure may be too late

TAMPA — Agricultural researchers, bolstered by the infusion of hundreds of millions of dollars from the federal and state government and growers themselves, seem confident a solution will be found to eliminate or slow the spread of citrus greening, an insidious disease that already has claimed tens of thousands of acres of Florida’s signature crop.

The catch is that today’s promising research could take five years or more before becoming available to farmers. That may be too late for an industry that creates a $10.8 billion annual economic impact, employs nearly 62,000 people and farms more than a half-million acres.

“Solutions are being implemented as quickly as can be accomplished,” said Harold Browning, director of the Citrus Research and Development Foundation in Lake Alfred. “Obviously, time is short, and groves and growers are having to make difficult business decisions every month, every season. There are reasons for optimism in emerging solutions, but we won’t know the impact until the tools are in the hands of the growers.”

While research for a cure continues, the citrus crop continues to dwindle.

The U.S. Department of Agriculture on Friday issued its initial forecast for the 2015-2016 Florida orange crop. The USDA estimates a harvest of 80 million boxes, down 17 percent from last season, which produced nearly 8 million fewer boxes than the year before.

“We expected the estimate to be lower than the prior year so this really isn’t too much of a surprise,” Michael Sparks, executive vice president and CEO of Florida Citrus Mutual, the state’s largest grower’s association, said in a statement released Friday. “We are in a challenging time right now with severe disease pressure.’’

The USDA makes its initial estimate each October and revises it monthly as the crop takes shape until the end of the season in July.

Citrus growers in Florida are not sitting idle while research plows on and their groves shrink.

Florida Citrus Mutual spokesman Andrew Meadows said growers are about to file an emergency petition with the Environmental Protection Agency to get permission to use a couple bactericides already approved for peach and apple trees but not for citrus. If approved, the use of oxytetracycline and streptomycin compounds could be available for use on citrus trees by the spring.

“We’ve been doing field trials and they show good promise in knocking back the (citrus greening) bacteria,” Meadows said. “That’s a big ray of hope for growers right now.”

Growers over the past nine years have diverted some $90 million from their marketing budget into research to try to save their industry from ruin. The federal government has pledged $125 million over a five-year period, of which this is the second year, Meadows said. Another $8.5 million came from the state government last year, with an additional $8.5 million budgeted for this year.

Browning, with the Citrus Research and Development Foundation, said the disease is a threat to citrus crops across the nation, not just Florida. He noted citrus greening already has shown up in Texas and is now threatening California.

“A national response is appropriate, and it will be critical that the federal funding support the continuation of discovery research across the U.S.,” he said.

All for research on how to stop an industry-killing bacteria spread by the Asian citrus psyllid, a marauding bug the size of an apostrophe.

Researchers are approaching the problem from a variety of angles. Methods now range from steam treatment to chemical and organic applications. One researcher is dabbling in nanotechnology to stem the spread of the disease that infects trees in groves large and small.

Citrus greening, also known by its Chinese name Huanglongbing, or HLB, causes orange, grapefruit and other citrus trees to produce small, bitter fruits that drop before they are ripe. It takes a few years, but infected trees eventually wither and die.

There is no known remedy, only ways to slow its destruction.

Some possible solutions include hot steam treatments of trees under plastic tents, and the use of benzbromarone, which has long been used to treat gout in humans.

The use of benzbromarone looked promising when researchers sprayed greenhouse tree shoots with the compound and found that it had halted the citrus greening bacteria in 80 percent of the infected trees’ shoots.

Other researchers are looking at ways to kill the bugs that spread the bacteria, and creating new strains of trees that are immune to the disease. The development of bacteria-resistant root stock is a long-term solution, though, as it could take a decade or more before they are perfected in the laboratory, put in the ground and grow into fruit bearing trees.

Among the potential solutions is the development of Zinkicide, created by Swadeshmukul Santra, an associate professor in the NanoScience Technology Center at the University of Central Florida in Orlando.

Zinkicide is designed to kill the citrus greening bacteria, but how it’s delivered is what makes it unique.

Citrus greening is difficult to control by traditional bactericidal spray methods because the bacteria lives inside a tree’s fruit, stems and roots in the vascular tissue known as the phloem. There, it deprives the tree of nutrients, causing root loss and ultimately death.

For a bactericide to be effective against citrus greening, it must be able to move within the plant, Santra said in a statement released by UCF this summer.

Zinkicide is a nanoparticle smaller than a single microscopic cell, and Santra believes it can move from cell to cell to kill the citrus greening bacteria.

“The bacteria hide inside the plant in the phloem region,” Santra said. “If you spray and your compound doesn’t travel to the phloem region, then you cannot treat HLB.”

Zinkicide is derived from ingredients already found in plants and is designed to break down and be metabolized after its job is done, he said.

“It’s a 100-year-old disease, but to date there is no cure,” Santra said of citrus greening. “It’s a killer, a true killer for the citrus industry.”

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