[NAFEX] Citrus Greening is spreading.

athagan at atlantic.net athagan at atlantic.net
Thu Sep 22 09:51:40 EDT 2005

Diversity in plantings is good.


Published Friday, September 16, 2005
More Citrus Greening Found
One Polk County citrus official says it's a scary prospect that the
disease may be spreading.

By Kevin Bouffard
The Ledger

AVON PARK -- State and federal inspectors have confirmed 23 new cases
of citrus greening disease in southeast Miami-Dade County and found
two suspected outbreaks in Coral City and Miramar, about 40 miles
away from the initial discoveries of the bacterial disease that is
fatal to trees.

If confirmed, the Coral City and Miramar outbreaks would heighten
citrus industry fears that citrus greening may be spreading across
Florida beyond control.

"It's very scary," said Chris Oswalt, the citrus agent for the Polk
County Cooperative Extension Service in Bartow. "Conventional wisdom
is it's probably a lot worse than anything we've had."

Oswalt was one of the organizers of the 2005 Florida Citrus Growers
Institute, a day-long seminar on growing issues Thursday at South
Florida Community College in Avon Park. More than 100 growers,
industry professionals and academics participated.

That included Tim Gottwald, a plant pathologist at the U.S. Department
of Agriculture in Fort Pierce, who gave a less-than-optimistic
outlook on the chances for controlling the spread of citrus greening
in Florida based on the experiences of growers in Asia, Brazil and
South Africa who have dealt with the disease for years.

Greening killed about 60 million citrus trees of all varieties during
the 1990s, Gottwald said. In Brazil, it has spread outward about 120
miles from the site of the original discovery during the past 10

"In reality, it's quite likely more widespread than that," he said.
"Anywhere in the world where it's been found there's been no
effective control."

Agricultural inspectors discovered three cases of greening between
Florida City and Pinecrest in southeast Dade in late August. That
initiated a survey of about 150 square miles around those cases.

Inspectors found greening on 32 citrus trees on 23 properties during
the follow-up survey, said Denise Feiber, a spokeswoman for the
Florida Department of Agriculture and Consumer Services.

The northernmost confirmed case emerged in Key Biscayne, about 10
miles to the northeast of Pinecrest across Biscayne Bay, she said.
The southernmost find remains Florida City.

Officials say they hope to have results from lab tests on the Miramar
and Coral City discoveries today, she said. Feiber could not say how
those two suspected cases were discovered.

One factor that will make greening difficult to control is that the
Asian citrus psyllid, a moth found commonly across Florida, carries
the bacteria and spreads it efficiently, Gottwald said. The psyllid
is the primary method for spreading the disease once it gets

The other problem is the psyllid prefers to live in two ornamental
plants very common in Florida, the orange Jessamine and the China box
orange, Gottwald said. Controlling the disease could involve
widespread destruction of those plants as well as fruit-bearing
citrus trees -- oranges, grapefruit, tangerines and limes.

The citrus fruits least susceptible to citrus canker -- another
bacterial disease that has destroyed more than 6 million trees
through a state-federal eradication program -- are the most
susceptible to greening, Gottwald said.

The greening bacteria also are difficult to detect because it can live
in a tree for up to three years before symptoms emerge, he added.

Another difficulty in detecting the disease is that the greening
bacteria do not spread uniformly throughout the tree, Gottwald said.
That means a sample taken from one part of the tree may test negative
for the bacteria even though it exists elsewhere in that tree.

An adequate detection program would need to collect thousands of
samples, which would quickly overtax the state's lab facilities.

Taking all those factors into consideration, Gottwald estimated a
control program would have a "fair to low" chance of keeping greening
in check if the bacteria could be confined to the Dade area where it
exists now.

If the disease spreads beyond Miami, he said, "the chances are low."
If it moves beyond Dade into southeast Florida, the chances to
control further spread are "very poor."

The greening bacteria attack the tree's vascular system, which carries
nutrients throughout the plant.

An infected young tree will not reach maturity, and an infected mature
tree will produce significantly less fruit until it dies. The fruit
it does produce is small with a high acid content that gives it a
bitter, salty flavor.

Kevin Bouffard can be reached at kevin.bouffard at theledger.com or

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