Pesticides still effective despite rising resistance levels in aphids
Despite the discovery of aphid resistance to the most commonly used pesticides in Munster in 2013, farmers can still effectively control the pest, provided they know what they are looking for, writes Teagasc horticultural researcher Michael Gaffney.
While the Knock Down Resistance (KDR) gene was first discovered in Cork and Tipperary two years ago, only grain aphids with one copy of the resistance gene have been located here since.
This suggests that this is not a 'full' resistance, but instead a loss in sensitivity to pyrethroid sprays.
We don't know the extent of the resistance gene in the Irish population yet, but with reports of significant Barley Yellow Dwarf Virus (BYDV) in early sown autumn crops, it seems that pyrethroid sprays may be set to be less effective.
If a grower suspects that resistance is an issue, they should initially establish the species of aphid present.
If a wide range of aphid species are present, it's likely that there was an issue with the application of the pyrethroid. If only grain aphids are present, then you should contact your advisor and apply a non-pyrethroid insecticide if available and required. Advice on how to identify common cereal aphids will be available during the Crops Open Day.
Other issues in relation to aphid control for farmers is the reservoirs of infection.