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A Better Fruit Fly Trap
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Fruit flies caught in a trap.
(K9427-1)
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As early as 1929, the Mediterranean
fruit fly—Ceratitis capitata, or medfly—had made its mark in
the fruit orchards of Florida. From a distance, a veritable cornucopia of
fruits and vegetables—peaches, pears, peppers, plums—may have looked
pristine, but on closer inspection, the "hole" truth revealed itself.
The adult female medfly damages ripe fruit by making a hole and depositing her
eggs under the skin of the fruit. Once the larvae hatch, they satisfy their
ravenous appetites by feeding on the pulp inside the fruit, rendering it unfit
for human consumption.
After apparently being eradicated by 1930, the medfly was spotted again in 1956
in Miami. Since then, periodic infestations have occurred in California, Texas,
and Florida. |
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Chemist Robert Heath inspects captured
flies in a modified McPhail trap.
(K9424-1)
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ARS efforts to prevent establishment of
medfly, as well as all other fruit flies, have led to development of a new,
recently patented trapping system that will help fruit growers control this
formidable pest.
Of the world's many agricultural pests, the medfly remains one of the most
destructive. The USDA's Animal and Plant Health Inspection Service estimates
that the medfly alone would generate agricultural losses of about $1.5 billion
a year if it were to become established in the continental United States. These
losses would result from export sanctions, lost markets, treatment costs,
reduced crop yields, deformities, and premature fruit drop. |
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The improved version of
the McPhail trap uses a
combination of three
chemicals to attract male
and female fruit flies.
The older version of the
trap used a protein bait
that captured large
numbers of nontarget insects.
(K9426-1)
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In response to this potential threat,
ARS chemist Robert R. Heath and entomologist Nancy D. Epsky have invented a dry
trap that combines chemical and visual stimuli to more effectively control
fruit flies—including the medfly. The work was done at the ARS Center for
Medical, Agricultural, and Veterinary Entomology, in Gainesville, Florida.
Traditional methods for monitoring, controlling, and eradicating fruit flies
have relied on traps that use a variety of chemical compounds or protein.
"Chemical attractants are effective in attracting male fruit flies but not
females," says Heath. "The traps also use sticky materials to retain
the captured insects. These materials are difficult to use, and they require
extensive maintenance," he adds.
Since female fruit flies need protein to ensure fecundity, protein is used in
traps to attract them. One such device currently being used for
monitoring—the bell-shaped McPhail trap—is baited with protein. But
it's cumbersome and has disadvantages, such as difficulty in baiting the trap
and removing trapped insects. Traps using protein baits also capture large
numbers of nontarget insects. |
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Fruit flies attack many fruits
and vegetables. Below: Fruit fly
larvae feast on surinam cherries.
(K9428-1)
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A newer version of the trap uses a
combination of chemical and visual stimuli to attract and trap the fruit flies.
"A key to its success is its ability to capture both female and male fruit
flies and to trap females before they've had an opportunity to lay their eggs
in fruit," says Heath.
The chemical stimulus is derived from three chemicals that have been isolated
from food baits—ammonia, putrescine, and trimethylamine. The three
chemicals lure the flies into the trap, where they are enticed to feed on a
panel that contains a feeding stimulant and toxicant.
"We've found that female fruit flies prefer different release rates of the
ammonia-and-putrescine blend," says Heath. "This discovery allows us
to selectively capture sexually mature or immature unmated flies or sexually
mature mated flies by varying the amount of the chemical blend," he adds.
The cylindrical shape of the trap provides the visual stimulus by mimicking the
three-dimensionality of host fruit. Clear panels at the top and bottom take
advantage of the flies' instinctive desire to move toward light, where the
lethal, sugary toxicant awaits them.—By Jesús
García, Agricultural Research Service Information Staff.
This research is part of Crop Protection and Quarantine, an ARS National
Program (#304) described on the World Wide Web at
http://www.nps.ars.usda.gov.
Robert R. Heath is in the
USDA-ARS Subtropical Exotic Pest Insect Research Unit,
U.S.
Subtropical Horticulture Research Station, 13601 Old Cutler Rd., Miami, FL
33158; phone (305) 254-3643, fax (305) 238-9330. |
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"A Better Fruit Fly Trap" was published in
the May 2001
issue of Agricultural Research magazine.
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