The world's first field trial of genetically modified (GM) wheat that produces its own insect repellent is reported to have been a failure. The publicly funded experiment, run by Rothamsted Research in the U.K, is a significant blow to the researchers, but they're confident that important lessons have been learned and that they can build on the results in future trials.  

“As scientists we are trained to treat our experimental data objectively and dispassionately, but I was definitely disappointed,” admitted Huw Jones, who co-authored the study published in Scientific Reports.

The researchers had hoped that by modifying the wheat to produce a chemical pheromone that repelled aphids, farmers would no longer need to intensively spray insecticides on their crops. Whilst the GM plant worked well in a laboratory setting, the scientists failed to reproduce the results in the field, finding no significant difference in pest numbers between the modified plant and normal wheat.  

“We had hoped that this technique would offer a way to reduce the use of insecticides in pest control in arable farming,” explained Jones. “As so often happens, this experiment shows that the real world environment is much more complicated than the laboratory.”

When attacked, aphids produce a certain chemical that alerts other insects in the area to the threat, prompting them to scatter. Many plants, such as peppermint, have managed to use this to their advantage and produce their own pheromone that mimics this smell. This not only repels the aphids but also attracts their predators, such as wasps. The researchers managed – to great critical acclaim – to take the pheromone gene from peppermint and insert it into a strain of wheat, nicknamed “whiffy wheat.”

The plant's field trial, which took place from 2012 to 2013, was the subject of many anti-GM protests and campaigns. In fact, while the trial itself cost just over $1.2 million (£730,000), the research team had to spend an extra $693,000 (£440,000) on fencing to protect the test area, and a further $2.8 million (£1.8m) on security measures to keep protesters out after threats and attempts to uproot and destroy the plants were made.

Why the GM plant failed to work is not yet known, although scientists have their suspicions. When attacked, aphids release their warning smell in bursts and spurts, but the GM wheat is modified to produce the pheromone continuously. The researcher’s suspect that this could result in the aphids becoming accustomed – or habituated – to the odor, meaning it loses its potency and therefore its effect on the insects.

But other experts note that while disappointing, the results are still highly valuable. “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 from the University of Cambridge. “This field trial is an excellent example of the sort of work that is needed.”