The sterile insect technique, or SIT, has been used for decades. Insects are irradiated so they become sterile, and then they’re released into the wild where they find mates. However, since they are sterile, there are no offspring, thus trimming the population and the threat to agricultural crops. The technique has been used effectively against the Mediterranean fruit fly, called the Medfly, and the cattle-infesting screwworm fly, among others.
SIT is considered a preferable alternative to spraying pesticides over urban or suburban areas near major ports. Irradiated, sterile flies dropped over seaports and agricultural areas save food crops and millions of dollars in prevented infestations and the ensuing eradication efforts.
Florida spends roughly $6 million a year using SIT to prevent Mediterranean fruit fly infestations, while California spends about $17 million a year. However, blasting the insects with radiation via electron beams, X-rays or gamma-rays, tends to make them weaker than typical males — and not so appealing to females as possible mates.
Now Florida researchers have found that sterilizing insects in a low-oxygen environment can boost the sterile males’ longevity as well as their ability to attract and successfully mate. They found that the positive effects of low-oxygen treatments even extended into their ‘old age’ — in the insects’ case, about 30 days under cushy laboratory conditions.
“Our males (insects) are not only more sexually competitive, they are maintaining their sexual competitiveness and their virility, into old age,” said University of Florida insect physiologist Daniel Hahn, “and that has the potential to make them much better biological control agents. Treatments that both improve the sexual performance of sterile males and maintain high performance longer in older males can substantially increase the effectiveness and decrease the economic costs of SIT programs.”
The “low-oxygen effect” has been known for decades, but the physiological basis for it had never been rigorously tested or analyzed, Hahn said. He and his colleagues suspected, and found, that under the low-oxygen conditions, the insects’ cells would produce antioxidants that can help better protect them from the off-target radiation damage.
Some operations that rear and sterilize insects, such as one in Guatemala that produces many of the sterile medflies dropped over Florida’s major ports roughly every seven days, do employ low-oxygen conditions, called hypoxia or anoxia. But many others don’t, he said, including those who rear and sterilize the cactus moth.
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