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Florida’s citrus growers are fighting to keep their trees alive. Since 2005, when the deadly citrus greening disease was first discovered in Dade County, it has become the single largest threat to Florida’s entire $9 billion industry.

The exotic disease, carried by the microscopic Asian citrus psyllid, kills the tree's entire root and branch system and doesn’t allow fruit to grow beyond the green stage. The scarred fruit usually falls off the tree and rots on the ground before it can be harvested.

Billy Teal, a production manager who has worked at Heller Brothers Packing for 25 years, says that he has never seen a threat as bad as this.

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“It’s a tree killer. Other problems we’ve had…freezes, floods, hurricanes, canker… we’ve gotten through, but greening kills the tree. It starves the tree of nutrients and it’s a slow, ugly death."

Citrus growers aggressively fight citrus greening by spraying fungicide in Fort Pierce, Fla. Dan Shepherd

Ten years ago, growers harvested over 200 million boxes of citrus throughout Florida, but today that number is almost cut in half. So far, retail prices have not risen much because growers have absorbed the costs, but prices are expected to increase at some point at the end of this year.

Michael Sparks, CEO of the Florida Citrus Mutual in Lakeland, Fla., says that the entire industry is in a chokehold.

“To think that we would lose Florida citrus is almost unthinkable. At the end of the day, that's the battle we are battling," he said. "Nothing has been this devastating to the Florida citrus grower."

At the USDA research lab in Ft. Pierce, Fla., David Hall and a team of scientist are hard at work looking for a cure.

“We're working 10 to 12 hours a day, we're working weekends…right now, it's our life. It's the toughest problem that I've ever been exposed to and, I guess the jury is out as to how soon we can deliver a solution.”

But scientists have made some progress as they look for new ways to keep citrus trees alive, such as heating the trees under 112 degree tents and injecting solutions of antibiotics and insecticides into the tree trunks.

For now, says Michael Sparks, don't count out the citrus grower.

“They're a resilient bunch and I still expect them to win the day before it's over," he said.