The Mexican fruit fly, Anastrepha ludens, is considered a significant quarantine pest that could cause billions of dollars in losses to citrus, peach, pears, avocado and other crops were it to move into the United States from Mexico.
But Mexico, in cooperation with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, has an aggressive programme in place to counter the threat posed by the pest and help maintain a “no-fly zone”.
Mexico uses the sterile insect technique, which involves sterilizing millions of male fruit flies with irradiation and releasing them en masse to mate with wild female flies. Such mating results in nonviable eggs that fail to hatch. Over time, repeated releases of sterile male flies cause the targeted pest population to collapse, diminishing or eliminating the need for insecticide spraying.
But the irradiation used to sterilize the flies weakens them, making it difficult for them to outcompete wild-type males for female mates.
Now, USDA’s Agricultural Research Service scientists and their collaborators have devised a hormone therapy for making sterile flies “more macho,” improving their chances of mating with female flies before their wild rivals do. Peter Teal, leader of the agency’s Chemistry Research Unit at Gainesville, Florida, developed the hormone treatment in conjunction with a team of scientists from Mexico, Argentina and Austria.
The team’s treatment uses a hormone analogue called methoprene to speed the rate at which sterile male flies reach sexual maturity while kept in specialized holding facilities. In studies, methoprene-treated flies were ready for release four days sooner than non-treated flies. And thanks to a dietary supplement of hydrolyzed protein, the sterile flies, once released, were also stronger and more successful at competing for mates.