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[nafex] FLORIDA Canker fighters review options
Thought you may find this interesting...
Published Wednesday, June 21, 2000, in the Miami Herald
Canker fighters review options
Choices beyond cut-and-burn are investigated
BY MARTIN MERZER
FORT PIERCE -- Alarmed by the tenacity of citrus canker as it marches
through Florida, state and international scientists debated a radical
approach Tuesday that could spare some of the millions of seemingly
trees in South Florida.
Maybe, some experts say, Florida will have to concede defeat, accept
Maybe we must live with the disease -- controlling it with chemicals,
windbreaks, frequent inspections and other relatively elegant measures
instead of invading yards and groves in a primitive attempt to root it
with bulldozers, chain saws and bonfires.
Among the promising avenues of research revealed during an
international canker summit: seven new ``induced systemic resistance''
compounds that can be sprayed on trees and might act as serums to
the resistance of citrus trees.
Canker management programs already are working in Brazil and Argentina
have largely replaced tree eradication campaigns there, about 80
and citrus industry executives were told during the International
Canker Research Workshop.
``Control programs are an option for Florida,'' said Wayne Dixon, a
canker expert and an organizer of the three-day event. ``We're still
eradication, but we want to see what else is out there.''
Programs to coexist with canker -- tolerating it at certain levels --
never been tried or seriously considered in Florida. That is changing
scientists search for a way to control the bacterial disease without
sacrificing more trees.
State workers already have destroyed nearly half a million citrus trees
South Florida and many more are on the chopping block.
``I'm known as `Satan' in Dade County,'' said Craig Meyer, the state's
deputy commissioner of agriculture, who runs the eradication program in
Miami-Dade and Broward.
Florida's current program, widely criticized as barbaric and wasteful,
condemns every infected tree and every other ``exposed'' citrus tree
1,900 feet of it.
It does not appear to be working. Despite eradication and a quarantine
blankets most of Broward and Miami-Dade, the disease already has spread
Palm Beach County and Collier and Hendry counties in Southwest Florida.
Next in line: Central Florida's sprawling groves, which produce nearly
billion worth of citrus every year.
Harmless to humans, canker severely blemishes fruit and eventually can
destroy the tree. There is no known cure.
Now, experts from as far away as California, Spain, France, South
and, curiously, Scotland, are at the canker summit, hoping to help
cope with its crisis.
Working in shirt sleeves amid a climate of urgency, they plan to emerge
Thursday evening with a comprehensive list of research recommendations.
Federal and state officials recently assembled $8 million to study the
disease. The summit's recommendations could include a new emphasis on
chemical and physical barriers to control canker's spread.
Among the methods used in Brazil and Argentina, and under study here
Spraying trees with compounds containing copper and, sometimes, other
chemicals. Growers in South America experienced substantial reductions
canker lesions on fruit treated with the substances.
``Copper is highly effective for canker control,'' said Pete Timmer, a
University of Florida researcher who has studied Argentina's program.
The substance must be used carefully, though, because too much could
Building windbreaks -- 300-foot-wide stands of silk oak, pine or other
noncitrus trees -- on the fringes of citrus groves. These trees, immune
the disease, can trap the bacteria and render it harmless before it
New serums. Sprayed on trunks, leaves and fruit, they already have
shown to activate and substantially improve trees' natural resistance
other bacterial diseases.
Tests on canker will start soon in Brazil and, possibly, Florida,
Replacing highly susceptible varieties of citrus with more resistant
``cultivars.'' Brazilian researchers have found several resistant forms
citrus, including the Valencia orange.
Comprehensive programs using these methods have replaced most tree
destruction projects in Brazil and Argentina, according to scientists
those countries, though some heavily infested groves still must be
One problem for Florida growers: The cost of sprays, equipment and
lost to canker can be high, raising production prices by hundreds of
per acre and possibly making Florida citrus less competitive in world
Another: The leaf miner, an insect prevalent in South Florida, works in
concert with canker to amplify the damage and complicate control
Wounds caused by leaf miners heal very slowly, allowing canker to
the tree with particular ease, Brazilian scientists said.
Meyer said an official policy of living with canker in Florida rather
ripping out trees is still months or even years away. Among other
environmental concerns about the use of certain chemicals could delay
But if ultimately adopted, the policy would save many South Florida
and avoid widespread anger and heartbreak.
Stephen Davis, a resident of Hollywood Hills in central Broward, said
orange trees in his yard were recently marked for destruction. Both are
healthy but apparently stand within 1,900 feet of an infected tree.
``It's going to be a terrible loss,'' he said. ``We enjoy the fruit and
shade and the animals that are attracted by the trees.''
A chemistry professor at Broward Community College, Davis fears that
wholesale removal of citrus trees -- many of them healthy -- eliminates
of the most hardy and resistant citrus.
At last count, eradication crews have destroyed 431,516 trees in
and 28,791 in Broward. Nearly all three million citrus trees in South
Florida could be cut down.
Residents believe their trees are being sacrificed to protect Central
Unfortunately, the return of summer rain and the hurricane season could
hasten canker's advance. The highly contagious bacteria spreads easily,
often hitching rides on wind-blown rain.
``We're getting into perfect weather for canker,'' said Mike Hunt, vice
president of Brooks Tropical Farms of south Miami-Dade, Florida's
lime producer. ``If it becomes very widespread in the state, they will
to give up on eradication and let everybody take their chances with
``Tell you the truth, it's something we'd like to try.''
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