Baiting traps with an attractant
such as minus-ceralure, Raw continues, "is more environmentally sound than
spraying insecticides and may be less expensive than releasing sterile male
medflies." These laboratory-reared, infertile males are set loose by the
millions when their wild counterparts are detected in traps. This prevents wild
flies from homesteading because no viable offspring result from a union between
sterile males and fertile females.
Not Just a Local Problem
Medfly woes aren't limited to the United States. The insect is a major
agricultural pest in Europe, Africa, Australia, Pacific areas, and Central and
South America. That's good reason for the researchers to patent the new
compound for worldwide use.
To help bring minus-ceralure to market, ARS is seeking a new cooperative
research and development agreement with the Farma Tech International
Corporation in Fresno, California, which has historically commercialized medfly
Working at the ARS Insect Chemical Ecology Laboratory, Raw teased out the
potent attractant from among the 16 isomers that make up minus-ceralure's
parent compound, ceralure. Developed in Beltsville and Hawaii and patented in
1988, ceralure's 16 isomers have the same chemical formula, but each differs in
its 3-dimensional structure. The most attracting of these turned out to be
Birth of a New Bait
Ceralure's inventors, chemists Roy T. Cunninghamnow retired from the
Hawaii laboratoryand the late Terrence P. McGovern, from the Beltsville
laboratory, pinpointed several isomers that they thought were key to ceralure's
effectiveness. But limitations of laboratory technology during the 1980s and
early 1990s made it impossible for them to extract and purify a large enough
quantity to test on the insects.
Using modern techniques, Raw developed a 9-step synthesis that yields 1 gram
of isomer for every 7 or 8 grams of starting materiala yield of 15
percent. His innovative procedure is a central part of the new patent he and
Jang are seeking ("Attractant for the Mediterranean Fruit Fly, the Method
of Preparation and Method of Use," U.S. Provisional Patent Application No.
60/176,192). And it produced enough of the isomers to supply small vials of the
clear liquid for Jang to use in outdoor tests with caged and free-roaming
For the outdoor testing, Raw chose to purify two candidate isomers that had
most intrigued both Cunningham and McGovern. Later, Jang's tests in Hawaii
showed that minus-ceralure B1 was the best of those isomers.
The Beltsville laboratory continues to search for more efficient synthesis
of minus-ceralure. Large-scale production of this powerful attractant must be
economical before it can be routinely used in thousands of traps.
Meanwhile, Experiments Offshore
Jang's testssome 5,000 miles away in a leafy commercial macadamia nut
orchardwill help determine how long very small quantities of the chemical
remain attractive under all sorts of weather conditions.
"We're seeing how well the lure holds up through our hot, humid days
and our torrential downpours," he says.
The orchard, which looks somewhat like a grove of pecan or walnut trees, is
about a 10-minute drive from Jang's laboratory at the U.S. Pacific Basin
Agricultural Research Center. The grove makes an ideal site for the outdoor
trials because the trees aren't a host of medfly. That makes it easier for
Jang, technician Lori Carvalho, and others on the Hilo team to gauge
minus-ceralure's appeal to the thousands of sterile medflies they rear in their
lab and then set free in the grove.
They dab various quantities of minus-ceralure on cotton wicks inside the
traps, then hang the traps at carefully spaced intervals throughout the
orchard. Next, they turn the flies loose and check the traps every few days to
see which concentrations of the lure attract the most medflies for the longest
period. The orchard's neat, precise rows of trees make a perfect grid for
laying out these mathematically correct, statistically sound field studies.
"We want to pinpoint the least amount of chemical that we can use for
the longest lasting trap," says Jang. "Cost-effectiveness is
particularly important with minus-ceralure becausefor now, anywayit
costs significantly more to produce than trimedlure."
Minus-ceralure and ceralure are among the newest tropical fruit fly lures to
emerge from the strong 40-year collaboration between scientists at Beltsville
and their counterparts in Hawaii. Ceralure is a modification of
trimedlurewhich Beltsville and Hawaii scientists invented and is now the
world's most widely used medfly attractant.
Today, minus-ceralure ranks as the best medfly attractant yet reported. The
researchers are looking to improve on this discovery. Jang, for instance, is
continuing analyses of other promising chemicals. Their work may lead to an
even more potent lure for the destructive medfly.By
Judy McBride and
Marcia Wood, 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
Eric B. Jang is at the
USDA-ARS U.S. Pacific Basin Agricultural
Research Center, Stainback Hwy., P.O. Box 4459, Hilo, HI 96720; phone (808)
959-4340, fax (808) 959-4319.