Crop pests posing new threats to UK farmers

Scientists at the world-renowned Rothamsted Research have identified a growing threat from the grain aphid (Sitobion avenae), a major crop pest that can reduce farmers' yields by damaging cereal crops and spreading plant diseases, most notably the barley yellow dwarf virus (BYDV).

This new research, funded by a large consortium consisting of the Chemicals Regulation Directorate/Defra, Agrochemical companies and levy boards, suggests that grain aphids are becoming more resistant to the popular pyrethroid insecticides. Pyrethroids, also discovered at Rothamsted Research, account for a quarter of insecticide-based control agents worldwide and the reason for this increased resistance may be due to the number of grain aphids carrying the knock-down resistance (kdr) mechanism which has increased in frequency this year.

Whilst there is a suggestion that these problems could affect UK farmers as early as this autumn, research leader Dr Steve Foster of Rothamsted Research, said “Our research does give us cause for concern but we should not panic just yet because BYDV is also transmitted by the bird cherry-oat aphid which is a more important vector and there's no sign of kdr in this aphid yet”. He added that “when grain aphids are the main pest present then growers need to be aware that pyrethroid sprays may not be effective. If growers apply timely applications at the full dose rate and suspect that control has been poor then they should not spray again with a pyrethroid-based product but switch to an insecticide with an alternative mode of action.”

Two new publications have been released which will assist with management of grain aphids this autumn, including best practice measures to limit the risk of resistance and strategies that could be deployed if resistance is suspected during the autumn spraying period.

Both publications can be downloaded from www.hgca.com/pests