Print

Email story

Comment

Email editor

Disease places citrus in peril

"Citrus greening" is considered a bigger danger than canker and is spreading.

By Kris Hundley
Published November 22, 2006

ADVERTISEMENT [Times photo: Skip O'Rourke] Consumers are expected to see another increase in the price of orange products. See graphic

Slammed by canker and hurricanes, Florida's citrus growers are preparing for their worst harvest in 17 years.

But that's not the worst of it. The billion-dollar industry's future is looking even bleaker due to a fast-spreading, highly lethal disease that turns a tree's leaves yellow and its juice rancid, then kills the tree in as few as five years.

Citrus greening, carried by the Asian citrus psyllid, a flying insect slightly bigger than a gnat, was first found in South Florida in August 2005. Today infected trees have been found in 12 counties, including all of South Florida and as far away as Sarasota County.

The speed with which greening has swept the state has caught small to midsized growers off-guard. But the biggest players say greening is now their top concern.

"This is absolutely the most serious threat the citrus industry has ever had," said Mike Carrere, executive vice president of Lykes Brothers in Tampa, the state's second-largest citrus grower. "Canker debilitates a tree. Greening actually kills it."

Once a tree is infected, there is no way to stop the bacteria. The only option is to destroy the tree, then aggressively spray neighboring trees in an effort to reduce the population of bacteria-bearing insects. Spraying won't eliminate the pests, however.

Tim Gast, citrus horticulturist for Southern Gardens Citrus in Clewiston, the state's No. 3 grower, said scientists have compared canker to the common cold and greening to liver cancer.

Southern Garden's acreage in South Florida was one of the first commercial groves where greening was found. And since Gast's workers began aggressively looking for signs of the disease a year ago, they've found thousands of infected trees.

"It's probably been in the grove for three to five years," Gast said. "My excuse for never having seen it is that there are other reasons trees turn yellow. And the way we farm now, we don't look at individual trees."

But that's quickly changing. Southern Gardens, a subsidiary of U.S. Sugar, used to have five scouts on 21,000 acres. It will soon have 36 scouts combing the 16,500 acres that survived canker.

The workers will be looking for the psyllids, which swarm and deposit a bacteria when they feed on citrus leaves. They'll also be looking for symptoms of the disease, which can take as long as three years to appear: yellow mottled leaves and stunted, green fruit that tastes salty and usually drops to the ground.

Gast, who first encountered greening when he was managing groves in China in the late 1990s, said diseased trees have to be ripped out so they don't become bacterial buffets for psyllids on their way to neighboring trees. And after diseased trees or psyllids are found in a grove, growers have to apply pesticides to at least reduce the insect population.

Gast, who recently paid a greening expert $700 a day for advice, said options for controlling greening are limited and expensive.

"Scouting costs about $80 an acre and pesticides cost about $300 an acre," he said. "But we don't really have any choice. If you want to grow citrus in Florida, you have to do these things."

Though Southern Gardens and Lykes, which has not yet found greening in its groves, are scrambling to deal with the disease, they fear smaller growers are still fixated with canker. Early this year federal officials decided canker could not be eliminated, so it stopped funding eradication efforts. That has left growers trying to contain canker, which has claimed more than 80,000 trees in the state.

Now commercial growers have to respond - quickly - to this far more virulent disease. The citrus industry also has the challenge of dealing with abandoned groves and residential trees that may harbor the deadly greening bacteria. As of Oct. 25, federal officials identified greening in 575 residential trees and 221 commercial trees.

"It's going to be difficult to have the public be terribly cooperative about taking trees out of their back yard," said Lykes' Carrere, recalling the outcry and lawsuits that followed mandatory eradication of residential trees for canker.

Some scientists and officials say the ultimate solution to greening will come through development of a genetically modified citrus tree that is immune to the bacteria.

Though researchers are mapping the citrus genome and an Alachua company, Integrated Plant Genetics, has developed promising antibacterial technology, it would take money and nearly a decade to get a new species to market. And juice buyers would have to embrace genetically modified oranges.

Gast, of Southern Gardens, thinks there are few options other than genetically modified trees. "Either you don't have citrus juice at all and fresh citrus is very expensive," he said. "Or you have juice but you have to use more pesticides. Is that what people really want?"

Kris Hundley can be reached at hundley@sptimes.com or 727 892-2996.

Q and A: 

What is citrus greening?

Citrus greening, also called Huanglongbing (HLB) or yellow dragon disease, is a bacterial disease spread by a flying insect called the Asian citrus pysllid. It can take up to three years for an infected tree to exhibit symptoms.

How does greening compare to citrus canker?

Greening is much more devastating than canker because greening ruins the fruit and kills the trees. Fruit from canker-blighted trees can still be used for juice and canker does not kill the tree.

How did greening get to Florida?

The bacteria, which has harmed trees in Asia, Africa, the Arabian peninsula and Brazil, was apparently brought to Florida by someone smuggling in an infected citrus tree. An infected insect was first found in Florida in 1998, but the first infected tree was not found until August 2005.

How rapidly is greening spreading?

In late October, government surveyors found infected trees in 12 counties, including all of South Florida's citrus-growing region and as far away as Sarasota County.

[Last modified November 22, 2006, 00:29:25]