Image caption The hope is that the male fruit flies will seek out and mate with the wild females to pass on the gene

A UK biotechnology company has applied for permission to carry out the first field trial in Europe of a genetically modified insect.

If it receives approval, the company, Oxitec, will carry out a small-scale test of GM olive flies in Spain.

The aim is to combat this olive crop pest by releasing male flies that have a "female-killing gene".

If the GM flies can outbreed the wild flies, the female offspring will die - reducing the olive fly population.

Bumper crop Approximately 5 million hectares of farmland in the European Union

More than half of the world's supply of olive oil is produced in Spain

Olive oil fraud - where oils are mislabelled or cut with cheaper oils - has become such a recognised problem that the European Commission held a workshop earlier this year, dedicated to finding a reliable way to authenticate olive oil. Source: European Commission

The technology was created by the co-founder and chief scientific officer at Oxitec, Dr Luke Alphey.

"Olive fly is the single major pest of olive production," Dr Alphey explained.

"In a bad year, you can lose the whole of an olive crop.

"And it's a very hard pest to control; it's been treated with insecticides, but now there's a lot of resistance."

Olives are an important commercial crop in Europe; olive groves account for about five million hectares in the EU. And, according to Oxitec, the olive industry in Greece spends approximately 35 million euros (£30m) annually on insecticides to control olive flies - to prevent an estimated loss to the industry of 650 million euros.

Killer mosquitoes

Thousands of miles from the Europe's olive groves, the company is testing the ability of its technology to combat a lethal disease.

In Brazil, Oxitec and its collaborators are trialling genetically modified mosquitoes - releasing males with the killer gene in.

Media playback is unsupported on your device Media caption Dr Luke Alphey explains the aim of the planned trials.

The basis of the technology is to inject the insect eggs with the lethal gene - a chunk of genetic code that essentially programmes the flies to die as they're developing.

The scientists have tuned their modification so that it specifically kills females. And, in the laboratory, the scientists rear their flies with a dietary supplement that acts as an antidote to this killer gene.

This means they can breed and rear generations of their GM flies to release into the wild, and have a male-only population.

Image caption Oxitec is already trialling its GM mosquitoes in an effort to combat dengue fever in Brazil

Once those male GM flies are released, Dr Alphey explained, "they will seek out the wild females, mate with those females and then their female offspring will inherit that gene and as they grow up, they will die."

In the most recent trial in Brazil - in a town called Mandacaru - the company has reported a 96% reduction in the dengue mosquito (Aedes aegypti) population.

The scientists use almost identical technology in their fruit fly research, with the ultimate aim of rearing a female-killing strain of GM male flies.

"We have had years of lab experiments and cage experiments, and an experiment in a glasshouse in Crete," explained Dr Alphey.

"And the next step is the first transition to the field, which is what this Spain trial is."

If they receive permission from the Spanish authorities, the researchers will release GM flies around net-covered olive trees, to contain the insects and to prevent the experiment from "being swamped by flies in the environment".

Unpredictable environment

Media playback is unsupported on your device Media caption Researcher Martha Koukidou from Oxitec explains how to rear GM fruit flies

Helen Wallace from Genewatch, an organisation that monitors the use of genetic technology, has criticised the company.

A major concern, she says is that these non-native flies could have "undesirable genetic traits", such as pesticide resistance, which could spread into the wild population when the flies mate.

"We also don't think it's a very effective technology, "she told BBC News.

"These flies are not sterile. They will produce offspring and those female offspring are programmed to die at the larval stage, which means there will be lots of GM maggots in these olives."

But Dr Alphey says that years of incremental trials and safety testing have not shown "any negative effects on human health or the environment from the use of these insects".

Image caption The technique uses a micro-needle to inject the olive fly eggs with the lethal gene

The crop in for this planned Spanish trial will be destroyed after the test. And the company maintains that the specificity of their technology could have significant environmental benefits.

Dr Alphey pointed out that the male flies seek out and mate with the pest species, whereas chemical pesticides can affect a number of different insect species.

Oxitec's chief executive, Hadyn Parry said: "It will have to be approved by regulators in the EU and no regulator would approve a product that carries a health risk."

UK Environment Secretary Owen Paterson recently branded as "wicked" opponents of genetically modified (GM) rice enriched with vitamin A, highlighting his support of research into GM crops.

In response to Oxitec's application, a spokesperson for the Department for the Environment, Food and Rural Affairs (Defra) said: "It's crucial that scientific studies like this can go ahead, so we can gather the evidence required about GM technologies that could bring great benefits to farmers and the environment."

Hear more about this story on BBC Radio 4's PM on Thursday at 1700 GMT