Genetically modified fruit flies deliberately engineered to kill themselves off could help save fruit crops by controlling the pest population without the need for pesticides. That's the assertion of Oxitec fruit fly team leader Dr. Martha Koukidou, who spoke with www.freshfruitportal.com about the benefits of introducing these flies into the agricultural sector. In opposition is policy research and public interest group GeneWatch. Here, we take a look at both sides.

Mediterranean fruit fly trials are to be carried out in Brazil following official approval for the Oxitec project to take further steps for development.

The National Technical Biosafety Commission, a multidisciplinary body that advises the Brazilian government on biosafety matters, has given the green light for the Oxitec netted field experiments.

The U.K. pioneer in controlling insects that spread disease and damage crops is now putting together further work before those trials actually happen.

Koukidou explains how the current line of defense against pests like fruit flies is insecticides, but the project's aim is to reduce this usage and save crops as well.

The Oxitec GM fruit flies have a gene which interrupts female development and will only reproduce male offspring.

"We have developed a method whereby you release males in the environment and basically they seek and mate with the wild native females, but all of their daughters will die," she tells www.freshfruitportal.com.

"If you eliminate the females from any given population you are causing the whole population to reduce because it doesn't matter how many males you have out there, it's really the females that matter.

"In the case of fruit flies, it is the females that cause damage to agriculture by laying eggs into a fruit, lets say an olive, a peach or whatever else and this egg will develop and hatch larvae, usually maggots; we don't want to see that in the fruit.

The fruit then becomes prone to secondary infection as the pest tunnels its way through, leaving a hole that is open to bacteria.

"By releasing males and males only that means we do not cause any additional damage to agriculture because the males mate with the wild native females and they don't affect anything else because the whole method is based on mating.

"They need to mate with the females and by sustained periodic releases, the whole population will drop.

"We believe that this is one of the most environmentally-friendly techniques one can use because it’s totally species specific, does not rely on any chemicals, and does not leave any residue in the environment, the method is self-limiting."

Koukidou adds that Oxitec has carried out extensive cage separation trials using established wild populations of fruit flies that demonstrated 'complete elimination of cage population in less than three months'.

"We had excellent outcomes; so the next step for us would be to take those strains into the field.

"We know the term GM causes controversy, however if one looks closely at the technology they will see that it is species specific, it does not affect any other species or anything else in the environment because it relies on mating. And of course we know by default that one species cannot mate with another."

GeneWatch opposes Oxitec's fruit flies

GeneWatch director Dr. Helen Wallace has a very different opinion, believing that it's impossible to predict the long-term outcome possibilities of releasing genetically modified fruit flies into the environment and how, over a period of time, the pests will naturally evolve a resistance to dying off and quite possibly get into the food supply.

"A major concern is that the GM fruit flies are genetically programmed to die at the late larval stage and that will be when many of the flies are still inside when the female lays the eggs," Wallace said.

"They (Oxitec) already have been approved trials which have not yet taken place, but if those trials take place they will be releasing a GM male to outnumber the wild population by at least a factor of ten to one so we're talking about millions of GM flies being released and mating with the wild flies.

A key question for Wallace is 'where will the female offspring that do not survive into adulthood end up?' and is concerned one possibility could be the food supply.

"Obviously we are concerned about environmental impacts because we’re talking about complex eco systems and a method that is very different from the irradiated flies that they (Oxitec) like to compare it with; so the irradiated ones are sterile, these ones will reproduce and only the females die so male GM adults can survive for multiple generations and it’s almost inevitable that they will spread.

"The technology also uses the antibiotic tetracycline, this is widely used in industrial agriculture and you get high concentrations of it in the environment particularly in animal faeces for example.

"So there is a very real prospect that GM flies will find contaminated areas where they can breed normally and there’s also potential for resistance to develop as the flies evolve. It would be difficult to contain this if anything went wrong."

Photo: GM sterilization on the horizon for fruit fly fight

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