"Because half of its offspring die, and no females can pass it on, the trait naturally declines in a population over time," Morrison said. Field and lab trials have shown that after just a few generations of no viable female offspring, the GM moths eventually vanish from the population, he said. "The desire is to reduce the damage to the crop by reducing insect population, not eliminate the species," Shelton noted.

Oxitec has also done lab and field testing with self-limiting mosquitoes, specifically Aedes aegypti -- the species that carries dangerous diseases such as Zika virus, yellow fever and dengue fever -- in South and Central America. The company is currently waiting on EPA approval of a self-limiting mosquito for testing in the U.S.

But its moth trials are farther along in the U.S., and Morrison is optimistic that farmers could see them in the commercial pest control market within the coming decade. That will take additional field tests and approval from regulatory agencies such as USDA's Animal and Plant Health Inspection Service (APHIS). So far, the field testing did not reveal any significant differences in behavior among GM and wild moths, nor did studies find any impacts on non-target species, Shelton said.

In earlier greenhouse trials at Cornell, scientists found that the GM moths could also lower insecticide resistance, since the released GM males contain no insecticide-resistant genes common in wild populations, Morrison said.

"The males introduce insecticide-susceptible genes out there into the population," he explained. "So as well as reducing the population, they're diluting resistance to insecticides and enhancing effectiveness of insecticides within a season."

Oxitec is working with other agricultural pests, such as fall armyworm and soybean looper, in South America. Bt resistance is a growing problem with fall armyworm, and laboratory studies at Cornell suggest the GM moths -- and other future self-limiting insects -- could slow that type of insect resistance, as well, Shelton said.

"When we introduced the genetically engineered male moths in the lab, it not only suppressed the population but it also lowered the frequency of Bt-resistant alleles in the population and brought back susceptibility to the population," Shelton said.

The recent field tests also showed that the moths are unlikely to stray too far from the field where they are released, a common concern among skeptics of GM insect development. More than 95% stayed within 35 meters of the release site, Shelton noted. "We've known this for a long time about diamondback moths. If they have good quality food and environment, they tend to stay there."

Even if the moths do catch a wind current and move to different fields, such as an organic field, the GM insects would die off after a few generations, he added.

Ultimately, Morrison hopes the GM moths and other future self-limiting insects could provide farmers with a novel mode of action to supplement current pesticides on the market.

"I think they might work best as part of an integrated pest management approach by taking advantage of the relative strengths of other tools, such as insecticides or biocontrol products," he said. "Our approach would be suited to work alongside them. It would be highly complementary and sustainable."

See the Cornell and Oxitec scientists' recent field testing work here: https://www.frontiersin.org/….

Emily Unglesbee can be reached at Emily.unglesbee@dtn.com

Follow her on Twitter @Emily_Unglesbee.

(PS/CZ )

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