Thousands of GM insects developed by British scientists are set to be the first released into fields in Europe as an alternative to chemical pesticides.
The plan is to release a large number of genetically modified olive flies that would be used to kill off wild pests that damage the crop.
The technology is the brainchild of experts at British company Oxitec, who insist the GM insects are better for the environment that spraying crops with chemical pesticides.
However critics fear the development could put human health at risk if people eat the flies or their larvae if they reach food products.
The trial would involve releasing genetically modified male olive flies which would mate with the wild females with the result that all the female offspring would die at the larvae or maggot stage. In theory, this would lead to a big reduction in the olive fly population so allowing the trees to produce fruit without using chemical sprays.
The Oxford-based firm has applied to Spanish regulatory authorities for permission to carry out a netted field trial of its GM ‘Frankenfly’. If successful, further trials would be carried out in Greece and Italy, while the company also hopes to be able to use GM insects in British fields.
Oxitec has developed a genetically modified strain of the diamond back moth, whose caterpillars are known to attack cabbages, broccoli and similar crops in fields in this country.
It would destroy the wild pests in the same way as the GM olive flies. Laboratory trials with the GM olive flies led to the elimination of the wild pests in less than two months. The system has also completed greenhouse testing.
Oxitec’s Dr Martha Koukidou, who is leading the trial, said: "Our approach is aimed not only at controlling the olive fly, but also to avoid harming other species. ‘By using our form of genetic sterility our flies are designed to eliminate the pest and not to stay in the environment."
The company has applied to the Catalan regulatory authorities for permission to conduct a field evaluation of its olive fly strain, in accordance with EU regulations.
The trial would take place under a net canopy surrounding 24 trees and carried out in partnership with the Spanish company, OpenNatur.
Its spokesman, Victor Perdrix, said: "We have been looking for a highly effective and environmentally sound solution for olive fly. We believe this holds great potential."
Oxitec insisted it has the support of some olive farmers, such as Paul di Calabiana Willan, who is based in Como, northern Italy.
He said: "On the mountain terraces here, agriculture depends on the success of olive plantations, but in recent years the olive fly pest has wiped out several harvests. The main weapon against the olive fly is a chemical which has been banned in some countries. Nothing else is effective.
In my view the use of GM insects to eradicate this pest is a necessary step towards achieving zero pesticide use."
The Oxitec chief executive, Hadyn Parry, accused critics of the technology who warn of danger to health and the environment of scaremongering.
He said: "European agriculture is facing some severe challenges. The burden of agricultural pests is ever present while the number of control approaches is shrinking in the face of insecticide resistance and de-registration of existing chemical treatments.
To survive and prosper, European farming will need to evaluate and embrace new solutions and new technologies which are effective, sustainable and safe. If approved, this evaluation will be an important step to bringing an exciting new approach to the farmers who need it."
However, Dr Helen Wallace, director of GeneWatch UK, warned: "Releasing Oxitec’ s GM fruit flies is a deeply flawed approach to reducing numbers of these pests, because large numbers of their offspring will die as maggots in the fruit.
Not only does this fail to protect the crop, millions of GM fruit fly maggots (most dead, but some alive) will enter the food chain where they could pose risks to human health and the environment.
Oxitec’s experiments should not go ahead until rules for safety testing and plans for labelling and segregation of contaminated fruits have been thoroughly debated and assessed.
If these issues are ignored, growers could suffer serious impacts on the market for their crops."