Genetically engineered moth released for first time

Jan. 31 (UPI) -- Scientists have for the first time released a genetically engineered, self-limiting insect into an open field.

Researchers hope the field test marks the beginning of a turn in the momentum in the war between the diamondback moth, Plutella xylostella, and growers of brassica crops like cabbage, broccoli and cauliflower.

Every year, the diamondback moth, sometimes called the cabbage moth, does billions of dollars in crop damage. Scientists have been searching for a way to combat the pest without resorting to stronger and stronger pesticides.

Oxitec, a British biotechnology company, has developed a solution, a self-limiting moth strain.

In a first-of-its-kind field test, researchers at Cornell University released the company's genetically engineered males to interact and mate with their wild counterparts.

"The moth contains a gene that confers female-specific mortality in the larval stage," lead researcher Anthony Shelton, a professor of entomology at Cornell, told UPI in an email. "When the released males mate with females in the field, they carry the male-selecting, self-limiting gene and the female progeny from that mating do not survive, causing the population to decline."

In previous lab tests, modified males successfully competed for mates, passing along the self-limiting gene and stunting reproduction, but researchers need to be certain the genetically engineered moth behaved similarly in the field.

The results of the field tests -- published this week in the journal Frontiers in Bioengineering and Biotechnology -- confirmed that the Oxitec moth behaves as expected.

Scientists used a method known as mark-release-recapture to limit the impacts of the release. The engineered moths were marked with both a fluorescent powder and molecular marker and then recaptured using pheromone traps.

The latest study was designed only to confirm that the engineered male moths behave naturally in the field, but previous studies, including lab tests and mathematical modeling, have shown that repeated releases could control a local pest population without the use of supplementary insecticides.

"In addition to suppressing pest populations, this approach can counteract insecticide resistance in pest insects, and therefore can help protect or restore the effectiveness of existing pest management tools," Neil Morrison, researcher at Oxitec, told UPI in an email.

Most attempts to combat pests via genetic engineering rely on gene drives, which causes a gene, like one that causes sterility, to occur more frequently than it would naturally. The technique causes the gene to spread through the entire population.

"Gene drives and the self-limiting tactic we used are very different," Shelton said. "In the case of self-limiting insects, the gene is not 'driven' through the population and disappears over time."

With the success of the latest field test, researchers expect to conduct larger experimental releases of the Oxitec to document its effectiveness at reducing local pest populations.