BY JIM WAYMER
FLORIDA TODAYCall it canker on steroids.
Citing ineffective quarantines and other stopgap measures, a new warning from agriculture officials tells homeowners to get rid of backyard citrus trees and stop planting them.
The goal: Stop "citrus greening," which experts say could devastate the state’s $9.3 billion citrus industry.
"It’s the enemy at the doorstep," said Bud Crisafulli of Crisafulli Enterprises, which operates groves on Merritt Island. "If you’re a citrus grower, you’ve got to be concerned about this."
The Asian citrus psyllid spreads the bacteria that causes greening to citrus stems and leaves. While growers stay on the lookout and immediately destroy infected trees, backyard trees often are left to deteriorate and continue the spread of the incurable disease.
Officials acknowledge that convincing people to abandon their orange, grapefruit, lemon and lime trees may be going out on a limb in the Sunshine State, given citrus’ deep roots in Florida culture.
"People are attached to their trees. People love their trees. But citrus greening is a disease that many people have yet faced," said Nolan Lemon, a spokesman with the U.S. Department of Agriculture. "Trees that would normally thrive 50 to 100 years, you’re looking at them dying within five to 12 years of infection."
He and other officials hope people will get the message and hack down or burn infected citrus of their own accord. They don’t have the resources and have no plans to force homeowners to remove infected trees or to compensate them for doing so — as they did with canker.
They recommend homeowners plant alternatives to citrus such as peaches, mangos, papaya, avocado and date palm.
While oranges from trees with canker still can be sold for juice, greening makes oranges and other citrus taste bitter and salty. Infected citrus has yellow shoots, blotchy leaves and less fruit, which tends to grow abnormally small and lopsided.
"It’s definitely one of those diseases that’s required us to re-
examine how we’re going to combat it," Lemon said. "We’re going to have to live with this disease, at least for the short term."Widespread problem
The warning to take out affected backyard trees came among 23 recommendations recently from the National Research Council, a panel of agricultural scientists, in a 326-page plan for how Florida can contain citrus greening.
It said the disease has been found in all 34 citrus-producing counties in the state.
Linda Seals, an extension agent for the University of Florida, called citrus greening "widespread" in Brevard.
"We’re being hammered pretty bad," said Seals, who works in UF’s Palm Bay office. "We’re seeing it on new trees. We’re seeing it on old trees."
Experts say the Asian psyllid has spread throughout the southern United States and to California, Arizona and all other citrus-producing states, even Hawaii. The disease also is killing citrus in Brazil and most other major citrus-producing countries.
Scientists suspect the culprit insect may have stowed away on budwood imported from Asia. It was first seen in Florida in 1998.
The scientific panel warns that the disease, also called Huanglongbing (HLB) — Chinese for "yellow dragon disease" — may prove the industry’s hardest hit.
"The citrus industry has faced serious challenges in the past that have been publicized, but the industry has always been able to deal with them," the NRC panel wrote. "In this case, even under the best scenario, HLB is likely to change the industry permanently."
Surfaced in 2005
Although the insect arrived in Florida 12 years ago, because symptoms can take several years to develop, the disease didn’t become apparent in Florida until 2005.
By 2008, citrus greening and measures to contain it had cut Florida orange juice production by several percentages. Those losses are likely to increase, the NRC panel said.
A UF study two years ago found that greening could increase citrus production costs by about 40 percent.
Introducing some of the psyllid’s natural enemies — such as ladybugs and an Asian wasp — can help, but with little hope of eradication, biologists say.
Researchers in Vietnam found in recent years that planting citrus with guava nearly eliminated infestations by psyllids.
But the best solutions may be prompt removal of infected trees, the NRC panel said, or genetic engineering to make trees more resistant.
Something must be done, it said, to keep backyard citrus from thwarting growers’ efforts.
Carried on wind
The Department of Agriculture has no plans to force residential tree removal. That approach didn’t work for canker, a bacterial disease spread mostly by wind and landscaping equipment.
Hurricanes in 2004 and 2005 and lawsuits from property owners thwarted the agency’s attempts to eradicate canker.
In 2006, federal and state agriculture officials finally abandoned the losing battle to eliminate the disease and began to focus on containing it. They decided to no longer remove all commercial and residential citrus trees within 1,900 feet of infected trees and instead remove only infected ones.
The strategy on citrus greening so far has been one of containment. Quarantine zones run from Florida to Texas, Hawaii, Guam, as well as Puerto Rico and counties in California.
In November 2007, the USDA quarantined 28 counties in Florida because of citrus greening. By January 2008, the agency expanded the citrus greening quarantine zone to include the entire state of Florida.
Given the rapid spread of the disease, some experts question that strategy’s effectiveness and call for more aggressive tree removal, research and funding.
Early detection
Early detection may be the key, scientists say, at least to preventing further spreading.
Wonsuk "Daniel" Lee, an agricultural engineer at the University of Florida, uses aerial photographs and spectral analysis to save inspection man-hours and money and identify citrus greening early.
He has found that the bands of green to red and near infrared can differentiate infected trees from healthy ones.
"The healthy canopy and the infected canopy, they have different spectral signatures," said Lee, who holds some hope Florida eventually will get a handle on the problem.
"We have to, because it’s a $9 billion industry," he said.
The infected die
Melbourne’s Robert and Kathy Wiebel are learning about greening so they know what to do about the orange tree at their home in Peachtree Landing subdivision.
It yielded a few good years of oranges. Then last year, the leaves turned black and yellow and the fruit was dried up and useless
A test by the local extension office confirmed citrus greening. The couple trimmed off the infected limbs and plan to give the tree more time as it flowers. But they’re resigned to its demise.
Agriculture experts say all infected trees die, some within only a few years, and left standing, they serve as a source to spread the disease to other healthy trees.
"If it needs to come out, we’ll do our part and take it out," Robert Wiebel said.
Fear the psyllid
That sort of civic mindedness is solace for longtime local citrus growers such as Larry Harvey of Harvey’s Groves. He said his groves have no greening, yet.
"It seems like we’re getting all these new diseases and the old ones aren’t going away," Harvey said. "It’s getting a little harder every year."
Crisafulli also said he has yet to see greening in his Merritt Island groves. But he fears the Asian citrus psyllid.
He has more hope for genetically engineered trees resistant to the disease than he does for homeowners giving up their backyard oranges and grapefruits.
"You can’t tell them they can’t have a tree," Crisafulli said. "That’s what Florida’s all about."
Contact Waymer at 242-3663 or jwaymer@floridatoday.com.
Additional Facts
About citrus greening
WIDESPREAD THREAT: Citrus greening, or Huanglongbing (yellow dragon disease in Chinese), is considered the most serious citrus disease in the world. It’s thought to have spread to all 34 citrus-producing counties in Florida and in every major citrus-producing state and country. SIGNS OF DISEASE: The first signs are small yellow leaves on one limb or section of the tree. Other symptoms include yellow shoots, twig die-back, poor flowering and stunting. Fruit is small, poorly colored or lopsided. Fruit tastes salty and bitter.
THE CULPRIT: A bacteria is spread by the Asian citrus psyllid, first found in Florida in 1998, as it moves from infected to healthy trees as it feeds. It may have come from budwood imported from Asia. NO KNOWN CURE: Most scientists say there is no way to get rid of greening other than destroying infected trees, which usually die within 12 years. Experiments are being done introducing natural enemies of the psyllid and genetically engineering trees more resistant.Source: U.S. Department of Agriculture; Florida Department of Agriculture and Consumer Services
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