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December 1, 2005

Aromatherapy puts flies in the mood for love

Just a few teaspoonfuls of ginger root oil can improve the mating success of millions of males. Now, there’s a concept.

And it’s cheaper than the personal ads, too. For 11 cents, USDA researcher Todd Shelly can make a million sterile Mediterranean fruit flies just as competitive as their virile counterparts.

   fruit fly
  

Mediterranean fruit fly.
Photo by Jack Kelly Clark

The medfly can infest more than 250 fruits and vegetables, severely impacting California’s agricultural market. Not that long ago, treatment for Mediterranean fruit fly infestations meant insecticide spray treatments by helicopter. In 1996, the Preventive Release Program was introduced to control these infestations. The program involved aerial release of sterile flies. The aim is to have female flies breed with sterile males and fail to reproduce.

Shelly, a scientist from USDA-APHIS and the University of Hawaii, has proven that using a dose of ginger root oil amplifies the appeal of sterile medflies. Researchers coined the phrase “ginger root oil aromatherapy” to describe the process of using the aromatic chemical, ginger root oil, to increase the mating ability of medflies. This rise in ability even occurs from the mere exposure of the aroma to males for a few hours as young adults. The method is now in use in Florida (Sarasota) and California (Los Alamitos) and is also currently being tested in Brazil and Argentina.

With funding from the UC Exotics/Invasive Pests and Diseases Research Program, Shelly tested aromatherapy in Hawaiian coffee fields on the island of Kauai for three months. “Aromatherapy appears to ‘compensate’ for the behavioral deficiencies associated with mass rearing and make the sterile males good mating competitors,” says Shelly. “Producing and releasing millions of sterile males is largely a waste if these guys don’t mate. Ginger root oil aromatherapy appears to increase their appeal to wild females.”

From a mating and reproductive standpoint, Shelly’s research shows that “factory” males are inferior sexual competitors compared to wild males. “Females can distinguish between mass-reared males and wild males,” says Shelly. “How they do this is unknown, but it appears to depend on male performance during ‘close-range’ courtship. Once ‘close-range’ male courtship starts, females accept males exposed to ginger root oil more readily than non-exposed males. So, we suspect that these exposed males either perform certain elements of courtship in a slightly different manner or produce a different close-range pheromone, a chemical compound that attracts mates.”

So, why do males exposed to ginger root oil have a mating advantage? “In field and wind tunnel tests we found that ginger root oil hypes up males, “says Shelly. “They signal more frequently than non-exposed males.”

Ginger root oil contains the powerful male attractant, alpha-copaene. The oil can be purchased as a liquid and then applied to cheap dispensers such as cotton wicks or filter paper. In a second set of experiments, Shelly is investigating the effectiveness of panels impregnated with ginger root oil as a replacement for the liquid oil to speed up the procedure and eliminate the need to handle the oil directly.

He is conducting another set of mating trials in which males are exposed to the oil delivered via slow-release panels. Shelly is using what are known as “eclosion” towers at a joint CDFA/USDA rearing facility in Los Alamitos. An eclosion tower consists of 70 aluminum-sided trays stacked vertically, measuring 6 feet tall.

“About 25,000 medfly pupae are placed in a trough around the perimeter of each tray,” says Shelly. “Adults pop out of the trays and live between adjacent trays. We found that as little as 1 ml of ginger root oil boosts mating success of males in a tower. This is important because California will probably switch to this tower system in the next few years.”

Mediterranean fruit flies are one of many exotics pests trying to become widely established in California. New pests already cause an estimated $3 billion in damage to California’s urban, agricultural, and natural environments. The UC Exotic/Invasive Pests and Diseases Research Program targets research on exotic pests and diseases in California. The program aims not only to improve our knowledge and management of pests that are already here, but also to reduce the potential impact of those pests and diseases that pose a threat to the state. The program is collaboration between the UC Statewide IPM Program and the UC Riverside Center for Invasive Species Research.

Resources

High-resolution image (500KB) "Mediterranean fruit fly." Photo credit: Courtesy of UC Statewide IPM Program, Jack Kelly Clark. Photos are for use with this release only. All other uses see Legal Notices.

Contacts

Stephanie Klunk, Communications Specialist
UC Statewide IPM Program
(530) 754-6724

Todd Shelly, USDA-APHIS
Office 808-259-8822
Lab 808-956-3742

Joseph G. Morse, Ph.D., Professor of Entomology
UC Riverside
Phone: 951-827-5814
Fax: 951-827-2794

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