Non-potato colonising rose-grain aphids were one of the most important vectors for spreading potato virus Y in Scotland even though they couldn’t be seen in crops, warned Scottish Agricultural College’s Andy Evans.

“They are actually looking for cereal crops, but when they come across a potato plant they land on the leaf, probe it and then quickly fly off. They only spend a short time on the plant, but in this time they are able to transmit potato virus Y.”

In Fife, the borders and the lothians, there was a particularly high risk of transfer to seed crops, he said. “Numbers are unusually high in 2010 and without care could lead to high levels of virus next year.”

Controlling the number of potato volunteers would help reduce the virus spreading, he said. “Volunteers act as a virus reservoir, so removing them lowers the risk of disease transfer.”

In seed crops, aphicide treatments should be applied as soon as key aphid species started appearing in the crop or in traps, said Dr Evans. “Growers should regularly check aphid trap websites and monitor local water traps and suction traps.”

Pyrethroid sprays were the most effective option to stop cereal aphids probing leaves, he added. “But when potato aphids come in you need to start using some of the more persistent products such as neonicotinoids.”