GUAM PAPAYA INDUSTRY OWES RECOVERY TO WASP

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By Katie Worth

HAGATNA, Guam (Pacific Daily News, Aug. 5 - Papaya,
anyone?

A year ago, it looked like Guam residents might not be able to
make that offer much longer, as the island's papaya crops were being razed by an
imported killer three millimeters long -- the papaya mealybug.

Fortunately, however, scientists have come to the rescue and
Guam's papaya crops are now growing their way back to health.

In June of 2002, Rangaswamy Muniappan of the University of
Guam's Agricultural Experiment Station, with the help of biological control
specialists from the U.S. Department of Agriculture, began releasing three
species of microscopic, stingless wasps imported from Puerto Rico to combat the
destructive papaya mealybugs.

According to Muniappan, the parasitic wasp seeks out a mealybug
and deposits an egg inside of it. The egg then grows into a larva, and
essentially eats the mealybug from the inside out, thereby killing it, he said.

"It's been very, very successful," said USDA
biological control specialist Dale Meyerdirk, noting that at sites they've been
monitoring for the last year, papaya mealybug populations have dropped by more
than 95 percent.

Farmer Bernard Watson, who said his papaya crop was destroyed by
the bugs before the parasites were released, corroborated the data.

"The parasites have done an excellent job at controlling
the (mealybug) population," Watson said. "Before they started
releasing them, ... it was pretty bad. It almost brought a lot of people's
productions to a halt."

The papaya mealybug originated in Mexico, Meyerdirk explained,
and at some point jumped to islands in the Caribbean. When those islands' papaya
crops were wiped out, scientists went to Mexico to find the natural enemy of the
pests.

Scientists found the parasites that kill the Papaya mealybugs,
and after sending them to a facility in Delaware for extensive research into any
possible negative environmental consequences, they introduced them to the
Caribbean islands, and later to the U.S. mainland, which the bug later infested.
Those programs were successful, Meyerdirk said.

Hitchhiking

So when the papaya-killing bug found its way to Guam, probably
by hitchhiking on some imported fruits, the obvious solution was to import the
parasites as well, Meyerdirk said.

The papaya mealybug has spread from Guam to Palau, Muniappan
said, adding that he, Meyerdirk and USDA entomologist Richard Warkentin flew to
Palau last weekend to establish a similar biological control program there.
Muniappan said the bug had not yet been reported on Hawaii or other Pacific
islands.

The bug has an impact on many species of plants, Muniappan said,
including hibiscus and the ubiquitous plumeria. He said the bugs' saliva is
toxic to the plants, so when the bugs pierce the plants to suck out the sap,
they poison them.

The parasites shouldn't present a problem to the island,
Meyerdirk said, because their population decreases as the mealybug's population
decreases.

"But the parasite will never totally eliminate its host
because if it did that it would die out," he said.

There are other species of mealybugs, including the pink
hibiscus mealybug, that also plague Guam. Similar biological controls exist for
those bugs, but so far they haven't been implemented because they affect mostly
ornamental plants, therefore, there is less pressure to fund those projects.

But at least the papaya mealybugs are no longer a scourge to the
island, Muniappan said.

"Right now this problem on Guam is solved, and it didn't
cost the farmers anything," Muniappan said. "They are satisfied
because last year at this time they couldn't plant papaya."

The island's farmers are again
growing papayas, now that an introduced species of papaya-killing mealybug has
been mitigated by another introduced insect.

August 5, 2003

Pacific Daily News: www.guampdn.com 

 

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