British scientists are beginning work on a selective pesticide that would kill aphids while sparing bees and other benign insects.
The project at Rothamsted Research in Hertfordshire, one of the UK’s largest agricultural science centres, follows the recent completion of an international effort to decode the entire genetic sequence of the aphid or greenfly.
Professor Lin Field of Rothamsted told the British Science Festival in Guildford yesterday that new insecticides were needed desperately – and not just for gardeners to spray greenfly infestations on their roses.
“Aphids are the most important insect crop pests in Europe,” she said. Almost every vegetable and fruit is vulnerable to aphids, which spread plant viruses as they suck sap.
Sustained attack with pesticides over the past 50 years has led to the evolution of chemical-resistant aphids. Only one class of insecticides still works reasonably effectively against aphids, the neonicotinoids – which are very toxic to honeybees and have been blamed for the recent collapse of bee numbers in some parts of the world.
Knowing the whole DNA sequence of the aphid (500m chemical ‘letters’ altogether) is opening new avenues of attack, said Prof Field, who is also President of the Royal Entomological Society.
Rothamsted scientists are concentrating on the aphid’s “sodium channel” which is vital for nerve function. They have identified the gene responsible for the sodium channel and discovered the mutations that cause resistance to pesticides.
The honeybee genome has also been decoded, Prof Field added. “There is now the prospect of looking at the differences in sodium channels between aphids and honeybees and thinking of how a compound might be designed to bind to the aphid protein and not that of the bee, thus creating selective insecticides.”
Several years of research and development will be needed, in collaboration with the agrochemical industry, before farmers and horticulturalists can attack aphids with a new generation of selective pesticides. These might then move quickly into garden centres.
A potentially more controversial way of defending crops against aphids is also under development at Rothamsted. It uses the “alarm pheromone”, a biochemical warning that the insects give when attacked by predators such as ladybirds.
“We have transferred the gene for the aphid alarm pheromone into a plant,” said Prof Field. The idea is to put the insects off feeding on crops that give an alarm signal.
“We’ve got funds for a field trial but it’s a GM technology and that’s not very popular,” she said.