Potato, sugar beet and vegetable crops could all be vulnerable to earlier attacks from peach-potato aphids this season, according to Richard Harrington, an aphid expert from Rothamsted Research.

While official forecasts would be issued at the end of February, the mild conditions experienced so far made early aphid movement look likely, he said at a joint ADAS / Syngenta Vegetable Industry conference.

The trend towards later potato planting revealed by British Potato Council figures exacerbated the threat from earlier flights of Myzus persicae aphids, he said. “Crops will be at a younger stage when Myzus populations invade, with new growth more vulnerable to virus transmission and damage.”

Aphids on sprout

And just a 2C increase in average temperature would allow the aphid to start infestations a month earlier than normal and go through an additional four to five generations a year, he warned.

“Myzus can reproduce in less than a week at optimum temperatures. There is the potential to create up to 18 generations a season, multiplying 50 times with each one.”

That further increased to risk of resistance developing, Syngenta’s Michael Tait said. Monitoring by Rothamsted Research had shown that although knockdown resistance to pyrethroids had stabilised and in many situations pyrethroids remained effective, MACE resistance to carbamate insecticides was at a high level. The reduced use of organophosphate insecticides had resulted in a sharp reduction of aphids with high levels of esterase resistance.

“The good news for growers is there are sufficient insecticide options, with effective rotation of the different chemical groups the key,” Mr Tait said.

Other effects of climate change would be to increase problems caused by mealy cabbage aphids and cabbage root flies, while it might be increasingly difficult to keep Colorado beetle out of the country if conditions continued to warm up, Dr Harrington noted.