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Tiny Soldiers In A Citrus War: Sterilized Fruit Flies

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The Associated Press

Published: October 7, 2007

SARASOTA - Two or three times a day, laboratory
technicians load chilled metal boxes onto small planes at
Sarasota-Bradenton International Airport.

The boxes contain millions of foot soldiers in the state's war
against the Mediterranean fruit fly, a tiny pest that could
devastate Florida's $4 billion citrus industry.

When they reach 2,000 feet above southwest Florida, the boxes
are opened, releasing a shower of tiny bugs into the sky.

As it falls, the rain comes alive. Bodies once dormant from the
cold start to twitch. Tiny wings unfurl and flutter. If the
technicians have done their job right, the flies will never reach
the ground.

The federal government's secret weapon against the Mediterranean
fruit fly? Male flies made sterile by radiation.

About 70 million flies are dropped each week over Tampa, Miami
and about 160 square miles of Sarasota and Manatee counties, areas
considered a high risk for a Medfly outbreak because they have
major sea ports.

Although they are sterile, the flies' urge to mate has been
chemically fired up with the aroma of ginger oil. Their mission is
to lure the female fruit flies from their wild, fertile
counterparts.

The Sterile Insect Release Program is run from a small U.S.
Department of Agriculture lab near the airport. Introduced in 1998,
the program has helped keep Florida's citrus industry free of one
of agriculture's most destructive pests.

The program costs taxpayers about $3 million per year. Florida
citrus growers say that is money well spent.

The industry employs about 90,000 people and has an economic
impact of $9 billion, according to a University of Florida study. A
fruit fly outbreak would prevent Florida fruit and vegetables from
being sold in many other states and countries.

"This type of unique bio-control is important to keeping
Florida citrus certified for shipment to markets around the
globe," said Michael Sparks, CEO of Florida Citrus Mutual, the
state's largest growers organization.

If left unchecked, fruit flies "could cause millions of dollars
of damage to citrus and agriculture as a whole in Florida," he
said.
Fruit flies are attracted to 250 different types of fruit and
vegetables including avocados, grapefruit, guavas, lemons, mangoes,
tangerines and oranges.

The flies do not eat the produce. Rather, the females lay their
eggs under the skin of the fruit. Their larvae, which look like
maggots, then eat the fruit from the inside.

A female can lay about 800 eggs in her life. The eggs become
adult flies capable of reproducing in about 25 days.

Even with a survival rate of only 50 percent, a population of
100 Medflies could explode to 10 million in about 120 days.

"If we can find these things when (they number) five or 50 or
even 5,000, then we can win it," said Dr. David Dean, an
entomologist with the Florida Department of Agriculture and
Consumer Services.

The influx of visitors to Florida's beaches and theme parks adds
to the risk of a fruit fly outbreak.

Larvae can be brought in when travelers ignore regulations and
sneak fruit into the state. Fruit flies also arrive in shipping
containers or are inadvertently brought back by boaters from the
Caribbean.

"They can't get here on their own; they get here with the help
of people," Dean said.

Florida's most recent Medfly outbreak occurred in 1998. Medflies
were found in seven counties, including Sarasota and Manatee.
This year, crops in five countio release them, the screens are rolled into a
metal storage room kept at 38 degrees.

"All the little critters get cold," Renshaw said. "They wrap
their wings around themselves, release their feet and curl up into
a little ball."

Workers wearing hooded tops to ward off the cold load the
balled-up flies into metal release boxes from which they will be
dropped. One box typically holds about 95 pounds of flies.

In the plane, an augur device under the box controls the release
of the flies, dropping 125,000 per square mile.

Medflies are also attacked through a ground-based program.
Around 250 fruit fly trappers keep tabs on roughly 60,000 traps
from Key West to Jacksonville.
Every fly caught is checked for traces of the vibrant orange dye
that signifies it is a sterile male.

If a wild fly is found, state and federal agencies go into
emergency mode.
That happened in July, when trappers in Tampa found a male
Oriental fruit fly. More than 500 traps were set in an
81-square-mile area around Valrico, east of Tampa, where the fly
was found. No other flies have since been found.

Before the release program, outbreaks of fruit flies were
treated by spraying malathion, a pesticide, from planes. The
measure was unpopular with the public who feared it posed a health
risk.

Now, any area with an outbreak would be inundated with sterile
flies from the Sarasota facility.

"The flies are much more efficient because they find each
other. We've got biology working for us," Dean, the entomologist,
said. "We do that long enough, we can totally eliminate the
species."

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