A genetically modified wheat strain developed in the United Kingdom and designed to repel pests has failed to do so in field trials.

The wheat strain had been genetically engineered to give off pheromones mimicking insect alarms to scare away pests such as aphids while attracting their natural predators, and while successfully tested in the laboratory it failed to repel the damaging aphids during outdoor field trials, the disappointed researchers announced.

Developed at Rothamsted Research, an agricultural science institute near London, the GM strain had raised hopes wheat crops could be grown with less need for insecticides.

However, in the field aphids still made a meal of the grain, researchers said.

"The disappointing thing was when we tested it in the field we didn't find any significant reduction [in aphids]," said Rothamsted chemical ecologist Toby Bruce. "We didn't get the result that would have been useful in taking this forward. It was quite sad."

Compared with a control crop of wheat, the GM crops showed no improved yields, no reduction in aphids and no increase in attacks by aphid predators such as ladybugs or wasps, the research team reported in the journal Scientific Reports.

Aphids are a serious problem for wheat farmers, feeding on sap, and harvests in fields infested with aphids can be reduced significantly.

The genetically modified strain showed promise in laboratory experiments, repelling three types of aphids and attracting parasitic wasps that are an aphid predator.

However, when the researchers moved to field trials, planting both engineered wheat and non-GM control strains in 16 test plots, the GM wheat failed to perform as expected.

When those field trials started in 2012, they drew protests by anti-GM campaigners who staged demonstrations at the Rothamsted trial site and threatened to destroy the crop.

That resulted in the need to make the site secure, adding around $2.8 million to the study's $1.1 million research costs.

Despite the encouraging lab work, the trial results were unambiguous, researchers notes.

"The field is the ultimate arbiter," says chemical ecologist John Pickett, who led the work. "This hypothesis was tested false."

Still, other experts in the U.K. said the overall approach is still worth pursuing despite the disappointing trials.

"We are in urgent need of new ways to control insect pests on crops, with very limited options available from pesticide sprays and conventional breeding," said Ottoline Leyser, a plant biologist at the University of Cambridge. "Alternative approaches ranging from new agricultural practices to genetic modification must be explored."