A pest aphid which nicotine doesn’t kill

Three of the pesticides called neonics (neonicotinoids) are under a temporary ban here in Europe. It’s because there’s evidence that they kill bees.

Of course bee-killing isn’t the reason neonics were used, and still are used in several countries. They’re used to kill pest insects. One of those pests is a greenfly called the peach potato aphid (Myzus persicae) which is widespread and common. It sucks plant sap and transmits plant viruses, leading to serious crop losses.

This pest has evolved a subspecies called M. persicae nicotianae which can suck tobacco (Nicotiana tabacum) plants. Here’s the science from Rothamstead Research. To live on that plant, the peach potato aphid has to survive the nicotine which makes tobacco insecticidal.

All aphids make an enzyme called CYP6CY3. That’s their defence against nicotine but in countries where the climate doesn’t suit tobacco farming, such as North Western Europe, there aren’t so many Nicotiana spp. plants. Garden plants of that genus but not whole farms of them. So if you’re an aphid in North Western Europe you can survive well with just two copies of the gene for CYP6CY3. Or you could, until people started using neonics. Neonics are synthetic pesticides which have a lot in common with nicotine.

The new science from Rothamsted describes how the nicotine-resistant aphids manage to be nicotine-resistant. They have many more copies of the gene for CYP6CY3. Did they get that way by evolving under the selection pressure of neonics? That’s not known yet. But it’s plausible, isn’t it? Professor Lin Field at Rothamsted says that the new knowledge about aphid genes ‘can be utilised when developing pest management strategies.’

The aphid research at Rothamsted was part-funded by Bayer CropScience. That company makes neonics and it’s taking legal action against the European neonic ban. Perhaps Bayer will invent another way to get ahead of the greenfly, in the arms race between pests and pesticides.