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Citrus Greening

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By RUSSELL RAY

rray@tampatrib.com

Published: December 21, 2008

FORT MEADE - In an orange grove east of here, rows of tree stumps mark the hard reality of an endemic disease that growers fear could cripple Florida's $9.3 billion citrus industry.

Larry Black, who oversees 1,600 acres of citrus trees for Peace River Packing Co. in Fort Meade in Polk County, has cut down and removed nearly 1,700 trees since August 2007, when citrus greening disease was detected in one of his groves.

Black is doing all he can to keep the disease from spreading, but he continues to find more infected trees. The symptoms of greening are obvious: yellowing leaves, lopsided and greening fruit, and dark seeds.

"Just driving by, I can pick out a handful of positives that need to come out," Black said.

Discovered in South Florida three years ago, greening has spread to all 32 citrus-producing counties in Florida, the leading citrus-producing state, with nearly 600,000 acres devoted to commercial production. As the industry commits millions of dollars to new research to find a cure, growers' costs are soaring because they're spending more on fertilizer, insecticides and inspection to limit the spread.

"The grower who isn't proactive is at great risk of going out of business," Black said.

Greening, also known as yellow dragon disease, attacks the tree's circulatory system and eventually kills the tree.

It's Carried From Tree To Tree

State officials suspect the disease entered the state through a seaport in Miami, perhaps in some ornamental plants from China. The disease is carried from tree to tree by an insect known as the Asian citrus psyllid, which feeds on citrus leaves.

"We need to understand how the psyllid specifically transmits greening," Black said. "There was never a need to control the psyllids until the greening was detected."

Knowing how the disease is transmitted may help researchers identify a way to stop the spread of greening, he said.

Black sprays his trees about eight times a year with a chemical engineered to kill the bug that spreads the disease. He has also hired a special contractor to inspect trees for symptoms.

"You're talking about a 25 percent increase in our costs to inspect and combat the psyllid," he said.

The industry isn't sure how many trees have been lost to greening so far, but Michael Sparks, chief executive of Florida Citrus Mutual, a growers' organization, said the disease could wipe out Florida's citrus industry if left unchecked.

"This is the most serious disease the Florida citrus industry has ever encountered," Sparks said. "What the grower is doing right now is trying to survive. They're holding on until the research can give them some clear directions."

Sparks said psyllids don't like guava and that researchers are working to develop a kind of "guava juice" that could be sprayed on citrus trees to keep the bug and the disease at bay.

But that's a short-term fix. A long-term solution would be a disease-resistant tree, but a breakthrough of that magnitude may be a decade away.

What's more, a citrus tree can be infected with greening for up to two years before showing any symptoms, a trait that keeps growers on constant alert.

"You can have it and not even know it," Sparks said.

While some growers are fighting hard to ward off greening, others are doing little to combat the disease because of the added expense.

"You've got some growers who feel this is the end of the line," Black said.

Black pointed to a neighboring grove, where the grower is doing minimal disease control.

"He sprays maybe once a year," Black said.

Abandoned Groves A Threat

Abandoned or neglected groves are a threat to nearby working groves because they can become a breeding ground for the psyllid, the bug that spreads greening.

In one grove, Peace River lost about 700 trees to greening. Black suspects the disease spread from the abandoned grove next door, where the trees aren't sprayed.

"There are groves like that all over the state," he said.

Black would like to see the industry adopt a regional approach in battling greening disease.

Since 2006, greening has contributed to an 11 percent decline in the amount of land used for commercial citrus production in Florida. Commercial acreage has dropped to 576,577, the lowest level since the U.S. Department of Agriculture began tracking citrus acreage in 1966. Commercial citrus acreage peaked in 1970 at more than 941,000 acres.

Polk County is Florida's largest citrus-producing county, with 81,375 acres committed to commercial production. That's down 5.8 percent from 86,398 acres in 2006. In Hillsborough County, commercial citrus acreage has dropped 24 percent to 11,248 during the same period.

But some growers, including Peace River, are replacing their losses with young citrus trees that will start bearing fruit in about four years. Peace River has planted more than 15,000 young trees this year, Black said.

"Holding back on planting is not an option because you're always losing trees," he said.

The cost of those seedlings, however, has doubled because the nurseries have taken steps to protect those trees against infection.

"All of the nursery trees are now grown in screen houses that have special mesh to keep the psyllid out," Black said.

GREEN MONSTER

CITRUS GREENING: Also known as yellow dragon disease, it attacks the circulatory system of a citrus tree and eventually kills the tree. There is no cure. The disease is spread from tree to tree by an insect known as the Asian citrus psyllid, which feeds on citrus leaves.

SYMPTOMS: Yellowing leaves, deformed fruit, dark seeds and a bitter taste.

Russell Ray

Reporter Russell Ray can be reached at (813) 259-7870.

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