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Last updated on April 18, 2014 at 15:19 EDT

Guatemala zaps fruit flies in nuclear pest war

March 28, 2006

By Mica Rosenberg

EL CERINAL, Guatemala (Reuters) – Every week, Guatemalan
scientists blast 2.7 billion fruit flies with radiation to make
them sterile in a bizarre nuclear war against one of the
world’s most destructive farm pests.

The flies, a threat to the fruit and vegetable industry in
California and Florida, are then dropped from planes to
copulate with fertile females in Guatemala, Mexico and the
United States.

Female medflies only mate once in their month-long lives
but can lay up to 800 eggs so barren procreation with sterile
males denies the chance of life for hundreds of potential
offspring.

As a pest control method, it is easier than killing flies,
which once they infect a crop can reduce yields by over 50
percent.

The MOSCAMED facility in Guatemala, which has a major
medlfy problem, is on the frontline in the fight against the
pest. It is the largest of 25 producers of infertile flies in
the world.

“The irradiation destroys the male reproductive organs;
there’s no sperm,” explained Oscar Zelaya, the director of
MOSCAMED who said the nuclear rays emitted at the plant are
about one-tenth the minimum needed to kill a human.

“The female feels satisfied after copulation but it’s
impossible for her to produce eggs,” he said.

At the plant near the town of El Cerinal, the acrid smell
of fly pheromones wafts through warehouses where millions of
the bugs are bred then heated in a vat.

The female eggs, genetically engineered for sensitivity to
temperature, will die at exactly 93 degrees Fahrenheit (34
degrees Celsius) so only the males remain.

They are grown on trays of sugar cane, wheat and yeast, a
specialized diet that nourishes the eggs to hatch into larvae.

BORN STERILE

In a matter of days, thousands of teeming larva will form a
cocoon called a pupa which is zapped with nuclear radiation to
stunt their sexual development. The flies then hatch sterile.

The medfly originated in sub-Saharan Africa, but in the age
of jet planes it can travel from an infested area like
Guatemala to the United States within a matter of hours.

Medfly outbreaks are now common all over the world, from
Albania to Zambia, but for the United States the biggest threat
comes from Mexico and Guatemala where the pest is more common.

“If we don’t catch them soon enough then an outbreak could
cost us hundreds of millions of dollars,” said Tomas Fasulo an
insect expert at the University of Florida.

The United States is free of largest-scale medfly
infestations but imports the sterile flies to keep the pest’s
population down.

The U.S. Department of Agriculture orders coordinated
fumigations to rid the country of the fly whenever there is
sign of an outbreak.

Although smaller than a housefly, the medfly is known for
particularly aggressive destruction of citrus, mangoes, pears
and other fruits.

Females will lay more than 75 eggs under the skin of a
soft, vulnerable fruit. When the larvae hatch, they burrow deep
into the fleshy interior of their new home, reducing it to an
inedible mass.

The fly then passes from fruit to fruit, tree to tree where
one female medfly can lay up to 22 eggs per day and hundreds in
her entire lifetime.

That is why the U.S. government helps fund Guatemala’s
MOSCAMED facility.

The plant exports about 408 million flies a week to the
United States and 650 million to Mexico, but more than 70
percent of the bugs from the facility are dropped in Guatemala.

The whole operation is funded jointly by the three
governments and MOSCAMED officials say there’s no commercial
profit in the impotent fly business.

Daily flights release bags of the chilled, irradiated pupa
into the wild, but confused farmers who have rarely been told
about the program are often surprised by the unusually large
number of flies falling from the sky.

“The people would say, ‘Before this used to be a clean
area,” said Ana Gonzalez a biologist who worked in Lachua, an
agricultural region in northern Guatemala. “But that was until
the planes came and dropped bags full of worms all over our
crops.”‘


Source: reuters