Scientists in Britain say they have developed a way of genetically modifying and controlling an invasive species of moth that causes serious pest damage to cabbages, kale, canola and other similar crops world-wide.

In what they said could be a pesticide-free and environmentally-friendly way to control insect pests, the scientists, from the Oxford University spin-off company Oxitec, developed diamondback moths with a "self-limiting gene" which dramatically reduced populations in greenhouse trials.

The self-limiting gene technique has already been tested against dengue fever-carrying mosquitoes, cutting their populations by more than 90 percent in trials in Brazil, Panama and the Cayman Islands.

"We're going to be injecting into diamondback moth embryos some DNA and we're hoping to integrate this DNA into the diamondback moth genome," said Oxitec research scientist Adam Walker as he prepared to modify an egg in the company's Oxfordshire laboratory.

"This takes two generations to occur, so the eggs that I'm injecting now we will rear up to adulthood. We will cross two members of the opposite sex and then we will look in the offspring for the presence of the fluorescent marker and that will indicate whether we've got integration of our gene into its genome."

According to the researchers, whose work was published in the journal BioMed Central Biology, the struggle with diamondback moths in cruciferous vegetable production costs farmers around the world up to $5 billion USD a year.

The researchers genetically engineered male moths that can mate just as well as the non-GM insects, but only produce male offspring. In greenhouse trials, releasing the GM moths into the population resulted in a crash in moth numbers within eight weeks.

As Neil Morrison, an Oxitec research scientist who led the study, explained: "If you release enough of our male moths over a sufficient period of time the pest population declines - and the great thing about this technology is that it relies on mating between a male and female moth and so the effect is very very target specific. It targets only the pest that you're trying to control but leaves other bugs flying around in the field unaffected and that might bugs that are actually quite beneficial to farmers, like pollinating bumblebees."

Tony Shelton, an entomology professor at Cornell University in the United States who worked with Morrison, said neither conventional nor organic pesticides can control the moths. He said the moths are developing resistance to insecticides.

To help the researchers in monitoring the GM moths, they carry a color marker. According to Morrison, "the color marker is only visible under special filters, so in normal light our moths look just the same as the pest moths flying around in the field. But the marker allows us to track and trace our moths in the field, so that in the normal way of things a farmer might monitor a pest population using traps that capture moths flying around in the field and if we use the same approach to monitor our moths we're able to track the pest moth population and the number of our moths that are flying in the field and continue to optimize it to achieve the appropriate number of released moths to suppress a given population."

Oxitec is keen to trumpet what it says are their research's impeccable environmental credentials. The scientists said that unlike insecticides, which can affect a range of insects including bees, the genetic modification approach is purely species-specific, only affecting the targeted pest. The self-limiting gene is also non-toxic, so birds or other animals eating the moths get no harmful effects.

"Diamondback moth is an invasive species in most of its range, so where we intend to control it we're actually probably changing the local ecology back to its natural state and the fact that it's so species specific means that, especially relative to other methods such as insecticides, means that the ecological footprint is very, very small," said Morrison.

Field experiments are now planned in outdoor conditions in New York. Oxitec's studies have already been approved by the U.S. Department of Agriculture.