TAMPA — Citrus greening, the insidious disease that is laying waste to Florida's signature agricultural industry, marches on with insect soldiers the size of a freckle that pass the lethal bacteria from tree to tree. There is no cure for the scourge that takes about five years to kill off a healthy tree and now has been reported in 37 of Florida's 67 counties, including Hillsborough, Pinellas, Pasco and Polk.
Last year, citrus greening was blamed for a loss of about 20 percent of the expected harvest, industry observers say. More worrisome, it's causing more and more citrus farmers to pull part of their groves out of production of Florida's iconic fruit — or get out of the business entirely.
Agricultural researchers continue to work to come up with a cure, which isn't on the horizon, or at least a way to control citrus greening, which every day seems more likely.
Preliminary predictions say that next season's yield will be down dramatically from years past, though some industry analysts dispute that. Over the past two decades, citrus growers have abandoned 300,000 acres, leaving a total of about 60 million trees on 500,000 acres.
Of that 300,000 acres lost, about 135,000 acres were abandoned because of citrus greening, said Mike Sparks, executive director of the Lakeland-based Florida Citrus Mutual, the largest citrus industry advocate in the state.
Still, growers are hopeful about the research that's going on, he said. That optimism is fueled by a new U.S. farm bill that, Sparks said, includes $125 million over the next five years to be spent on research into citrus greening.
Researchers have come up with some methods that extend the lives of infected citrus trees so they can continue producing fruit and keep the $9 billion industry afloat long enough for a cure to be found. One therapy involves heating sick trees to 128 degrees with material wrapped around the tree that uses the sun's heat. Tenting the trees for two or three days seems to delay the tree's demise.
“It doesn't kill the disease, but if you can do that, it gives another four or five years of productivity,” Sparks said.
He says other research into disease-resistant root stock also is promising.
“Encouragement,” he said, “is in the air.”
A hybrid peach tree, that a few years ago was being touted as a replacement for the Florida citrus crop has lost its luster, Sparks said.
“A peach crop here is a very nice niche market,” he said. “Some growers have five or 10 acres here and there, but I doubt we will see 500,000 acres of peaches. That's never going to replace the citrus crop here. The soil, the heat, the humidity, the rain; it's all perfect for citrus.”
The U.S. Department of Agriculture's Animal and Plant Health Inspection Service has imposed a quarantine on shipping out of state any citrus plant material, including nursery stock, to curb the spread of citrus greening to other states or countries.
The USDA called citrus greening “one of the most serious citrus diseases in the world.” Greening already has decimated crops in Asia and South America.
The citrus greening bacteria do not pose a health threat to humans, livestock or pets. The disease is transmitted from infected plants to healthy plants mainly by an insect called a citrus psyllid, which is the size of the head on a pin.
Symptoms associated with the disease first appear as yellow shoots or blotchy mottling and/or yellowing of the leaves, says the USDA on its website.
“As the disease progresses, the trees suffer excessive leaf drop and foliage becomes sparse with fewer or smaller leaves and tip dieback,” the website says. “The disease also affects the fruit, causing it to ripen unevenly and become lopsided, visibly smaller and bitter-tasting.
“Once the host plant becomes infected,” the website says, “there is no cure for the disease.”
Harold Browning is the chief operating officer with the Florida Citrus Research and Development Foundation, established by citrus growers around the state to work with the University of Florida in researching ways to benefit the citrus industry.
He said the citrus greening research is encouraging and that finding a cure in time to save the industry may be the biggest obstacle.
“We're doing everything possible to push the science faster,” he said.
A cure may be years away, so the focus of the research now is to keep the trees from dying so they can keep them producing tasty and juicy fruit.
There are different approaches, he said, mentioning the heat therapies as well as chemical solutions.
“Some antibiotics can knock the bacterium back the same way antibiotics work in humans,” he said. “They can slow down the decline and stabilize the conditions of the trees.
“That's the major thrust of the foundation's work right now, and it's proven effective,” he said. “None of these things are ultimate solutions. I hate to use the term 'Band-aids,' but these are methods to keep the productivity around while more durable solutions can emerge.”
The disease has taken its toll on growers, particularly small, family-owned groves.
“I'm not going to replant citrus,” said Richard Skinner, owner of Hawkins Corner Nursery in Plant City, who was forced to rip up 1,600 citrus trees last year after they had become infected with citrus greening. On the land where those citrus trees grew, some for 80 years, he will plant peas in the spring and summer and greens in the fall and winter to make the land productive.
“And I'm the microcosm of thousands of other little guys.”
He said planting another grove of citrus trees is too costly and the risk that it will be re-infected is substantial. Plus, it could be a half-dozen years before the newly planted trees start producing fruit.
“I'd be 80 years old before I get anything out of it,” he said,
Out of his nursery, he still sells small citrus trees for backyards. The quarantine doesn't apply if the trees don't leave the state.
He hasn't given up hope the state will win the battle over citrus greening, but he's not optimistic it will happen anytime soon.
“In the near future,” he said, “if you're addicted to orange juice or oranges, it'll be more economical to grow your own in your back yard.”