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Greening is newest threat to state's citrus crops

The disease, detected in Florida last month, attacks trees' vascular systems and makes their fruit bitter and unusable.

MIAMI - The tiny, disease-ridden insect lands on a bright green leaf of a healthy grapefruit tree, sucks out some nutrients and flutters away to the next plant.

In that instant, the once-productive tree begins its slow death, its veins and stems gradually choked by a bacterium that causes citrus greening, a worldwide threat to citrus plants that - along with citrus canker - menaces Florida's $9-billion industry.

The first U.S. discovery of the disease was reported last month. Since then, the U.S. Agriculture Department, state scientists, university researchers and citrus growers have begun grappling with the newest foe to Florida's famous and economically vital oranges, grapefruits and tangerines.

"It's devastating. It's just hard to comprehend," said Scott Hurley, vice president of the Becker Indian River Fruit Co. "We've been battling the canker issue for a number of years, and to have this thrown on top of it, it makes canker looks like child's play."

Unlike canker, which creates unsightly lesions on fruit, the citrus greening disease is deadly to crops. It already has infected and killed trees in Southeast Asia and Africa and had started attacking crops in Brazil, the world's largest producer of oranges, before being detected in Florida in September.

The average productive life span of trees in areas affected by citrus greening has dropped from 50 or more years to 15 or less. There is no known cure for the disease, which does not harm humans.

"The major thing is that it affects the productivity of the tree and the quality of the fruit," said Ronald Brlansky, a professor of plant pathology at the Citrus Research and Education Center in Lake Alfred.

Experts are still debating what is the most effective way to combat citrus greening. Some say the disease cannot be eradicated and that efforts should be directed at keeping it from spreading to uninfected regions. Others say it's too soon to determine the best solution.

The state has relied on eradication to deal with citrus canker. An aggressive strategy requires the destruction of citrus trees within 1,900 feet of one infected with canker. More than 9-million trees have been cut down. The disease itself doesn't kill the tree.

Canker surfaced in Florida more than 10 years ago and is moved by wind-blown rain. Greening, however, is spread by a tiny insect called a psyllid. Experts said the disease probably arrived in Florida from infected Asian plant material.

The Asian psyllid has been present in Florida since 1998, but psyllids can also be found in Texas. The disease affects the vascular system of the trees, eventually killing them. The fruit becomes lopsided and tastes bitter, rendering it unusable.

A sick tree will not show symptoms for a couple of years. Even when signs of the disease are present, samples must be tested because the telltale mottling and yellow discoloration can be evidence of other problems, such as nutrient deficiencies.

Officials are concerned that the disease has spread throughout the state and perhaps traveled outside Florida on infected psyllids that hitch rides on ornamental host plants that are shipped to retailers. A quarantine is in effect for certain ornamentals in Miami-Dade.

It's such a concern that the African and Asian strains are on the Agriculture Department's list of possible threats to plant and animal life that are regulated under the Agricultural Bioterrorism Protection Act.

Since the discovery of the disease in two pummelo trees in Homestead, the federal and state governments charted its spread.

It has moved from Miami-Dade north to Broward, then to Palm Beach, Hendry and Martin counties, said Richard Miranda, a spokesman for the state Division of Plant Industry. Officials are awaiting test results to confirm suspicions it has spread to St. Lucie and Monroe counties.

"We have responded very quickly," Miranda said. "We have already done as much as humanly possible to deal with this thing."

No eradication or control strategy has been devised yet because of several unanswered questions, such as how far has the disease spread; would widespread fumigation work; and how greening information should be distributed to homeowners.

"Nobody has given us any type of procedures to follow. Nobody has come up with any kind of guidelines. It's just a guessing game right now," said Hurley of Becker Indian River Fruit.

At an Oct. 14 meeting of state, federal and university citrus experts in Lake Alfred, some of the discussion centered on whether efforts should focus on eradication or merely controlling and managing the disease.

"It's a hard call to make," Brlansky said. "Any disease that's systemic - that you can have infection but you can't detect it - it's difficult to know how far it's spread. Eradication has not been successful in other areas of the world."

Scientists have found greening in Callery Grove in Loxahatchee in Palm Beach County. General manager Nat Roberts said greening was found in two tangerine trees along the border of a grove.

"It was one of about the worst days I've ever had when they called," Roberts said.

Roberts said the two infected trees have not been cut down because scientists want to study them further. But if he is asked to destroy trees in order to deal with greening, Roberts said he would likely comply.

Researchers are studying the outbreaks in Southeast Asia and Africa for clues on how to effectively combat the disease.

Miranda said efforts to stop the spread of the disease in Florida have dealt with not only commercial growers, but also homeowners. The state has sent representatives to inform homeowners that they have greening in their backyard citrus trees and ask them for permission to cut them down.

"We hope the public will learn that we are serious when we say this is a serious disease," he said.

[Last modified October 30, 2005, 01:12:10]