Date: Monday, November 26, 2007 Section: LOCAL IN-DEPTH
Edition: FINAL Page: B1
Source: Kumari Kelly, Sentinel Staff Writer
TURNING TO BUGS TO BATTLE EXOTICS
Scientists try to weed out harmful pests with predator species. Not all
are convinced it works.
Think of it as a boxing match: In one corner, the predators; in the other,
The predators: armies of beneficial insects. The prey: noxious weeds that
clog waterways and choke native plants or destructive bugs that threaten
sago palms, bromeliads or citrus.
The tactic, increasingly used in Florida’s sensitive ecosystems, is known
as “biological control.”
You pit the good bug against a bad bug or weed and hope the good guy wins.
But it isn’t nearly that simple.
It is a complex practice involving many scientists, years of research and
high hopes that the introduced predators don’t do more harm than good.
Biological control is seen as an alternative to pesticides and herbicides,
which are contributing to Florida’s pollution problem.
The practice is more than 100 years old, and Florida researchers have been
doing it for decades.
So far, they have unleashed about 70 predator species from other countries
into Florida’s environment, hoping to rid the state of pests such as
alligatorweed, the pink hibiscus mealybug, citrus canker, hydrilla and,
most recently, the Mexican “evil weevil,” which threatens to wipe out the
state’s native bromeliads.
Nationwide, hundreds of such predator species have been released. The goal
is to protect native species from falling victim to pests. Non-native
plants and animals, also known as invasive exotics, compete for the same
“What bugs me is that it’s easy to bring in these exotics,” said Bill
Overholt, associate professor of entomology at the Norman C. Hayslip
Biological Control Research and Containment Laboratory in Fort Pierce,
part of the University of Florida’s Institute of Food and Agricultural
He said exotic plants are routinely brought into the state from other
countries, many for the horticulture industry. About one exotic bug a
month likely piggybacks and becomes established in Florida.
“To bring in a natural enemy to control that plant once it’s become a
problem is a really complex and time-consuming process,” said Overholt, an
advocate for stronger regulations on importing invasive exotics.
Researchers do lengthy studies to make sure the predator won’t affect any
species besides the targeted prey or cause other problems for Florida’s
It can take several years from field study to final widespread release if
scientists discover the biological control seems to work.
In years past, there were unexpected consequences. Bugs went after
different species than scientists intended. Or they reproduced so much
they became a noxious pest themselves.
Success rates run about 30 percent, Overholt said, fueling criticism of
Pesticides are sometimes preferred because they are fast-acting.
“We aren’t very patient as a species,” Overholt said.
Not all dislike exotics
Though some view invasive exotics as damaging, others disagree.
Melaleuca, for instance, introduced from Australia as an ornamental, is
described as “Florida’s most infamous invasive species” by state
officials. It clogged the Everglades, so in 1997, scientists introduced
the melaleuca snout beetle, which feeds on melaleuca’s stems and leaves.
The tactic appears to be working.
Yet Florida’s beekeepers say melaleuca is one of the state’s top nectar
producers because it blooms several times a year, providing food lacking
elsewhere for honeybees. Beekeepers, who also sometimes rely on the exotic
and typically unwanted Brazilian pepper tree for the same reason, usually
oppose biological controls.
“They arbitrarily decide what’s a weed,” said longtime commercial
beekeeper Bert Kelley of Polk County, secretary of the Florida State
Today, scientists insist their methods are sophisticated and that they are
considering what is best for entire ecosystems.
“All the mistakes all happened . . . years ago,” said Ronald Cave, a
researcher at the UF facility in Fort Pierce who discovered the franki fly
— a new solution to bugs attacking Florida’s wild bromeliads. He also is
studying two wasps he hopes might combat Asian cycad scale, which is
wiping out the sago palm in Florida.
“It is no more appropriate to criticize modern biological control for
disastrous introductions of the distant past than to criticize modern
surgery for deaths through lack of antiseptic methods used in the past,
but many have learned from such errors,” said Cave’s colleague, Howard
Frank, a professor and entomologist at UF’s Institute of Food and
Agricultural Sciences, who is also working on the franki-fly project —
which is named after him.
Offering hope for crops
Biological control, some say, will be essential in the future, as the
world population is projected to reach 8.9 billion by 2050.
Despite use of chemicals, 30 percent of all crops are lost to pests in
developed countries, and presumably more in undeveloped nations.
Biological controls are one way to attack pests with or without the
cooperation of a landowner because bugs aren’t confined to property lines.
The Fort Pierce facility, which houses ongoing hydrilla research by
Overholt and Cave’s research on cycad scale and bromeliads, receives
$750,000 annually from the state through the Department of Environmental
Tom Broome, owner of The Cycad Jungle in Polk County and past president of
The Cycad Society, an international organization of enthusiasts who study
and collect the plants, said he holds little hope the parasitic wasps will
do much good.
“I’ve never seen the biological controls totally take care of the
problem,” he said. “It will help but never really takes care of it.”
Even Cave and Overholt agree that chemicals are a fast track to ridding a
problem pest and often are still the method of choice.
But research continues. At the Fort Pierce facility, Pasco Avery, who
holds a doctorate in microbiology and insect science from the University
of London, is studying citrus greening, a disease that can be devastating
to citrus trees.
The next possible predator out of the box: fungus.
Illustration: PHOTO: Michael Burton, a scientist at the Biological Control
Research and Containment Laboratory in Fort Pierce, breeds parasitic
franki flies that control the Mexican ‘evil weevil,’ which threatens to
wipe out Florida’s native bromeliads.
ROBERTO GONZALEZ/ORLANDO SENTINEL
PHOTO: Michael Burton works earlier this month at the Biological Control
Research and Containment Laboratory in Fort Pierce. Biological control, in
which a natural enemy is brought in to combat an invasive exotic, is seen
by some advocates as an alternative to pesticides and herbicides.
ROBERTO GONZALEZ/ORLANDO SENTINEL
PHOTO: Cane toad
CANE-TOAD PHOTO BY CARL SEIBERT/SOUTH FLORIDA SUN-SENTINEL
PHOTO: 1. Water hyacinth Hydrilla
A floating plant that was introduced to the U.S. during the New Orleans
Cotton Exposition in 1884.
PHOTO: MOTTLED WATER HYACINTH WEEVIL
Released in 1972, the weevils feed on the leaves of the water hyacinth and
PHOTO: CHEVRONED WATER HYACINTH WEEVIL
Released in 1974, weevils reduce plant growth and seed production but are
ineffective where lots of nutrients are in the water.
PHOTO: ARGENTINE WATER HYACINTH MOTH
Released in 1977, the larvae tunnel into young plants. Not so successful
because they aren’t widespread and disperse quickly.
PHOTO: WATER HYACINTH MITE
Native to the U.S., they can damage foliage but not enough to control the
PHOTO: 2. Brazilian pepper tree
This species is a native of Argentina, Paraguay and Brazil and is thought
to have been introduced into Florida in the 1840s as a cultivated
PHOTO: BRAZILIAN PEPPER-TREE SEED WASP
They are the only insect causing damage to Brazilian pepper-tree seeds.
PHOTO: 3. Water lettuce
Experts disagree whether this fl oating plant is a native or has been
introduced. Water lettuce occurs in lakes, rivers and canals.
WATER LETTUCE LEAF WEEVIL
From South America, they were brought to the U.S. in 1986 and 1988.
Distributed widely now but do not control the plant.
WATER LETTUCE LEAF MOTH
Imported from Thailand. Caterpillars released in 1990 but didn’t establish
PHOTO: 4. Hydrilla
It is a non-native submersed plant. It can grow to the surface and form
dense mats and can be found in all types of water.
PHOTO: HYDRILLA TUBER WEEVIL
From India and Pakistan, released in 1987. Larvae burrow into the ground
and eat tubers but have failed to establish.
PHOTO: ASIAN HYDRILLA LEAF MINING FLY
From India, released in 1987. Larvae burrow inside plant and kill up to 12
leaves each, but haven’t been effective.
PHOTO: AUSTRALIAN HYDRILLA LEAF MINING FLY
From Australia, released in 1988. Failed to grow widespread.
PHOTO: HYDRILLA STEM BORER
From Austrailia, released in 1991. Larvae burrow into stems. Ineffective
because larvae need sandy shore.
PHOTO: HYDRILLA TIP MINING MIDGE
Looks like a mosquito, and larvae attack plants and stunt growth. Under
evaluation for further use.
PHOTO: CHINESE GRASS CARP
From China, effective as a control for hydrilla because 2 to 25 fi sh can
control 1 acre of hydrilla, but they eat many types of vegetation,
damaging waterways. Genetically engineered ‘triploid’ grass carp are
sterile and are being used sparingly in a few small water bodies.
PHOTO: 5. Alligator weed
A prolifi c aquatic plant in 80% of Florida waters.
PHOTO: ALLIGATOR WEED FLEA BEETLES
From Argentina, released in 1964. Very successful in controlling the weed.
PHOTO: ALLIGATOR WEED THRIPS
From Argentina, released in 1967 and successfully control the weed on
PHOTO: ALLIGATOR WEED STEM BORER
From Argentina, brown moth released in 1971. Larvae burrow into the stem,
successfully killing the weed.
SOURCES FOR INFORMATION AND PHOTOS:
Center for Aquatic and Invasive Plants, University of Florida, and the
Bureau of Invasive Plant Management, Florida Department of Environmental
BOX: THE CASE FOR BIOLOGICAL CONTROL
*Uses fewer chemicals to control pests.
*Targets specific pests or invasive plants.
*Can, in some cases, be more economical than chemicals.
*Provides lasting relief from pests.
*Less harm to environment and water.
BOX: THE CASE AGAINST
*Can take longer than pesticides and requires lengthy research time.
*Takes more education, planning and management than most chemicals.
*Can negatively impact native species.
*Only targets one pest at a time.
BOX: OTHER BIOLOGICAL CONTROLS
* Snails: Used to control several species of aquatic plants
* Soda-apple eating beetle: From South America, approved in 2003 to eat
tropical soda apple, a plant from South America that looks like a small
* Lady beetles: Feed on aphids, mites, scales, mealybugs, whiteflies,
small caterpillars, beetle grubs and numerous types of insect eggs.
* Ant: Ants can help control caterpillars.
* Parasitic wasps: Almost microscopic in size, these are natural enemies
of caterpillars, grubs and aphids.
* Minute pirate bug (orius insidiosus): Attacks western flower thrips, a
pest that attacks strawberries, by sucking juices from its prey through a
BOX: SPECIES VS. SPECIES
On one side are pesky plants and harmful bugs that are ravaging Florida’s
waters and plants. On the other side are bugs, fungi and small animals –
warriors recruited by scientists to wipe out the enemy. Are the good guys
winning? Sometimes. Here are 5 examples.
SQUARES = THE ENEMY
CIRCLES = THE WARRIORS
BOX 3: GOOD TRIES GONE BAD
Northern curlytail lizard
Native to the Bahamas, introduced to Florida in 1940s for sugar-cane
pests, they spread and eat food sources of native birds.
From Asia, it was once touted to combat erosion but has spread
uncontrolled in many areas, choking other vegetation. It is considered a
From South America, introduced in Florida to control pests for sugar cane
but released accidentally at the Miami airport in 1955. They now compete
with native animals such as frogs and toads for food and have secretions
that can kill pets.
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