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Close-up of a screwworm larva. Link to photo information
Close-up of a screwworm larva. Tusklike mandibles protruding from its mouth tear the flesh of living warm-blooded animals. A wound may contain hundreds of larvae. Click the image for more information about it.

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An Improved Diet Helps Screwworm Control Efforts

By Alfredo Flores
March 15, 2007

A refined diet for screwworms that has been developed by Agricultural Research Service (ARS) scientists will help ensure that an ample supply of sterile screwworm flies can be produced to continue efforts to eradicate this pest.

For over 50 years, ARS scientists have provided leadership in intensive interagency efforts directed toward eradicating screwworms--first from the United States, in 1982, and then from Mexico, in 1991. Leading the way today are entomologist Muhammad F.B. Chaudhury, in the ARS Screwworm Research Unit's fly-rearing factory at Tuxtla Gutierrez, Chiapas, Mexico; and Steven Skoda, research leader of the unit's central office in Panama City, Panama.

The larvae that hatch from screwworm eggs cause great damage to livestock, wildlife and other warm-blooded animals as they burrow into and feed on their living flesh.

The key to eradication has been the mass-rearing of trillions of screwworm flies (Cochliomyia hominivorax). Once reared, young males are made sexually sterile and then air-shipped to other facilities for release in support of screwworm control programs that extend to Central America. Mating between native females and sterilized males produces no offspring, eventually leading to the pest's disappearance.

By conducting basic and applied research, ARS supports the Animal and Plant Health Inspection Service, the U.S. Department of Agriculture (USDA) agency in charge of ongoing screwworm eradication efforts.

For example, a new egg powder and molasses diet developed by Chaudhury for adult flies replaces the smelly, costly horsemeat-and-honey diet first used in the 1950s. The new diet is also easier to handle and more cost-effective. By replacing shredded recycled paper or a gelling agent with cellulose fiber to solidify and provide texture for the larval diet, the screwworm-release program can save $100,000 or more annually.

Skoda is working closely with the United States-Panama Commission for the Eradication and Prevention of Screwworms, which recently built a $40-million research facility in Panama City.

Read more about the research in the March 2007 issue of Agricultural Research magazine.

ARS is the USDA's chief scientific research agency.