A controversial GM wheat trial in the UK has failed after more than STG2 million ($A4.08 million) of public money was spent protecting it from eco-saboteurs.
The so-called "whiffy wheat" project to create a genetically engineered crop that wards off aphids by releasing an alarm signal scent cost STG732,000.
But this was dwarfed by the extra STG2,238,439 spent on fencing and other security measures for the field trial after threats of destructive attacks by anti-GM activists.
Campaign group GM Freeze claimed the scientists had wasted taxpayers' money in a pointless bid to "outwit nature".
Both the the trial itself and the steps taken to keep out the vandals, as well as earlier laboratory work, were wholly Government-funded through the Biotechnology and Biological Sciences Research Council.
After success in the lab, the genetically modified wheat turned out to be ineffective at repelling aphids in the outdoor trial conducted at the Rothamsted Research institute in Harpenden, Hertfordshire.
Disappointed scientists believe the insect pests may have become blase about the pheromone scent signal and learned to ignore it - much like people closing their ears to a constantly sounding car alarm.
"We now know that in order to repel natural aphid populations in the field we may need to alter the timing of release of the alarm signal from the plant to mimic more closely that by the aphid, which is a burst of release in response to a threat rather than continuous," lead researcher Professor John Pickett said.
The wheat was engineered with a gene derived from the peppermint plant that enabled it to release a pheromone called (E)-beta-farnesene (EbetaF).
Aphids use the alarm to alert each other to the presence of threats such as parasitic wasps and ladybirds. In the wild, the scent causes the insects to flee from danger - and also attracts predators that recognise the aphid signal.
In laboratory tests the GM wheat produced the pheromone in significant quantities without its appearance or growth being affected, and successfully repelled aphids.
But in the field trial there was no statistical difference in the number of aphids infesting GM and conventional wheat.
The findings are reported in the online journal Scientific Reports, part of the Nature publishing group.
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