LONDON (Reuters) - Field trials are under way in England of a genetically modified (GM) wheat that strikes fear into aphids and attracts a deadly predator to devour them, providing an alternative to the insecticides now used to control the crop pest.

The wheat emits a pheromone which aphids release when they are under attack to create panic and prompt the insects to flee, John Pickett, scientific leader of chemical ecology at Rothamsted Research in eastern England, said on Wednesday.

It also attracts tiny parasitoid wasps to provide a second line of defence for crops by laying eggs in the aphids.

"(It) eats the aphids from the inside out so it takes out the population on the crop," Pickett said.

"We are providing a totally new way of controlling the pests that doesn't rely on toxic modes of action," he told a media briefing.

The wheat has been modified using a gene found in peppermint plants, he added, although the smell was more like Granny Smith apples and too faint to be detected by humans.

Pickett said the field trials, at Rothamsted's research facility in Hertfordshire, used a spring planted variety of the wheat cultivar Cadenza.

He said the approach could eventually be used to protect other crops and flowers from aphids.

There are no other GM wheat trials currently being conducted in Britain although there are two involving GM potatoes.

Pete Riley, campaign director for campaign group GM Freeze, which opposes use of genetically modified organisms (GMO), said he had several concerns and believed there were better alternatives for controlling aphids.

"There are natural alternatives with which, if you design your farm right with plenty of cover and food for predators and parasitic wasps, you can control aphids pretty effectively and that has been demonstrated in the UK," he said.

"We don't see any need for this technology other than it is potentially more profitable to do GM than to tell farmers how to create the right habitats on their farms," he added.

Riley said that if the new wheat was produced commercially it could contaminate non-GMO varieties. He also questioned its effectiveness.

"We feel it is likely, if it is used very widely, that aphids would eventually get habituated to the chemical and not take any notice of it," he said.

(Reporting by Nigel Hunt; Editing by Anthony Barker)