The Potato Council said the peach-potato aphid, Myzus persicae, was first seen in a trap in East Anglia in mid-May, with more sightings over the next month.

"Research suggests vectors are coming into the crop earlier, so good virus hygiene on the farm is all the more important," said aphid specialist Drummond Todd.

Growers had to stay alert, he added, though there was no reason to think this would be a bad year for the bugs.

"Early roguing is key. Take out any ground-keepers and plants showing signs of virus. This reduces the risk of a virus spreading if aphid numbers increase."

The Potato Council's web-based monitoring service, www.potato.org.uk/aphids, carries area-based alerts for aphids.