No rise in common pyrethroid resistance in grain aphids, but new ‘super kdr’ changes detected

Two Teagasc studies find that the common knock down resistance (kdr) mutation in the English grain aphid has not increased in Irish barley fields since the 2018 neonicotinoid ban. However, genetic surveillance has, for the first time in this species, detected two additional mutations - including the “super kdr” M918L - signalling an early warning and the need for continued monitoring.

The English grain aphid (Sitobion avenae) is a major pest of cereals in Ireland and across Europe and an important vector of barley yellow dwarf viruses (BYDVs). In the absence of either resistant varieties and/or chemical control, BYDV can reduce yield and farm returns. One control option available to farmers is the pyrethroid insecticide; however, resistance to pyrethroid insecticide has been detected in grain aphid field populations.

Pyrethroids are an insecticide that disrupts insect nerve function, causing paralysis and death in affected insects. Insects have developed resistance to pyrethroids in several ways including mutations in the insects DNA which makes the chemical less effective. In Europe, the grain aphid is the only cereal aphid known to have developed knock down resistance (kdr) to pyrethroid insecticides.

Prevalence of pyrethroid resistance in grain aphids

Two recent publications from Teagasc researchers have looked at prevalence of pyrethroid resistance in grain aphids, both in the field and in the National Insect Suction Tower Monitoring Network.

This was part of a critical surveillance programme that included 155 winter barley crops surveyed over three years from 2021-2023. Additionally, grain aphid samples were tested from the Teagasc 12.2 m suction tower network from 2022-2024. In the absence of this surveillance, the sector would be blind to any risks to cereal crops that would result from changes in aphid populations.

Significantly, from both field and suction tower samples, there is no evidence of an increase in levels of knock down resistance to pyrethroid insecticides in recent years, which is good news!

However, the analysis did identify two new mutations occurring in the grain aphids from the National Insect Suction Tower Monitoring Network: M918L (a so‑called “super‑kdr” change) and L932F.  These variants have been linked with much stronger pyrethroid resistance in other aphid species. This is the first report globally of these mutations in the grain aphid.

The next step is to assess if aphids with these new mutations have established in Irish cereal crops so we can investigate the potential implications of these mutations for control.

What this means

• Good news: the common kdr mutation has not become more widespread in recent field surveys, and no fully pyrethroid‑resistant grain aphids were detected in the sampled crops.
• Caution: the appearance of new mutations is an early warning and while these new mutations were rare in the samples and were found in archived specimens, we do not yet know how widespread they are in crops or how much they reduce spray effectiveness in Irish populations.

Maintaining reliable control options

Maintaining a range of reliable control options as part of an integrated pest management (IPM) strategy is crucial for managing BYDV and resistance. The current lack of suitable alternative pesticides for cereal aphid control increases the risk of selection for pyrethroid resistance.

The detection of new resistance mutations highlights the importance of ongoing monitoring of both current and emerging pest and disease threats so we can build reliable, sustainable management programmes for growers.

Wider and continuous surveillance, including field sampling and suction‑tower monitoring, is needed to determine whether these new variants have become established in cereal crops. Where such variants are found, laboratory bioassays on live aphids carrying the mutations will be required to quantify resistance levels and to assess any fitness costs that might limit their spread.

Practical advice for growers

• Keep using integrated pest management (IPM) including monitor crops, encouraging natural enemies, and tolerant varieties where available.
• Report any unexpected spray failures to your Teagasc advisors; where practical, they will guide you in submitting samples for testing.

For more information or to send samples, contact Louise McNamara (louise.mcnamara@teagasc.ie) or Stephen Byrne (stephen.byrne@teagasc.ie).

Further information on these studies:

• M. Schughart, S. Byrne, M.T. Gaffney, L. Mc Namara. Irish Journal of Agricultural and Food Research (2026). DOI: https://doi.org/10.15212/ijafr-2025-00008 .
• Ballandras, V., McNamara, L., Carolan, J.C., Ruttink, T. and Byrne, S. The first report of M918L (super-kdr) and L932F voltage-gated sodium channel mutations in the English grain aphid (Sitobion avenae). Pest Management Science (2026), https://doi.org/10.1002/ps.71178