Main Objectives
For established resistance mechanisms, we will also use DNA-based diagnostics, which are specific for the mutation/s conferring particular types of resistance and we will incorporate any new such diagnostics as they become available (through other projects at Rothamsted). The need for our continued monitoring work is heightened by the presence of Myzus persicae with strong (Nic-R++) resistance to neonicotinoids in several European, including most recently Belgium, and north-African countries and their movement onto secondary crop hosts. The potential appearance of these aphids in the UK poses a major threat to neonicotinoid sprays that are still available to growers. For cereals and oilseed rape, the presence of pyrethroid resistance in the grain aphid (Sitobion avenae) and cabbage stem flea beetle (Psylliodes chrysocephala) in the UK highlights the volatility of resistance evolution and the need to continue monitoring for shifts in responses to currently effective compounds.
The proposed work is highly relevant to the co-ordination of research and decision making among agrochemical companies, grower organisations and advisors and the policy objectives of Defra-CRD. Furthermore, its importance is enhanced by EU-imposed bans on neonicotinoid use which have been extended to all outdoor crops, including sugar beet and cereals, and potentially other insecticide classes, coupled with the resistance situation for the remaining insecticides. The over-riding objective is to retain the availability of effective pesticides by developing appropriate Insect Management Strategies and providing robust scientific support to the regulatory decision-making process. Guidance will be available to advisors, growers and the scientific community through the Insecticide Resistance Action Group (IRAGUK). Other routes of communication will include articles in the trade press, presentations to growers and agronomists, and papers in referred journals. A copy of the Full Extension Proposal is available on request from Dr Steve Foster (Rothamsted Research, Harpenden, Herts., AL5 2JQ; telephone: 01582 763133 ext 2356; Email: stephen.foster@rothamsted.ac.uk)
This project is linked to previous work:
Combating resistance to aphicides in UK aphid pests.
Validating guidance for insecticide resistance management across commodities.
Outcomes / Key Message For Growers And Industry
- In 2021, we received, successfully reared and screened peach-potato aphid (M. persicae) samples (sent primarily by the sub-contractors, Dewar Crop Protection and ADAS.
- Screening bioassays applying diagnostic insecticide doses to live aphids from the M. persicae samples, continued to show no resistance to neonicotinoids, cyantraniliprole, flonicamid, spirotetramat or sulfoxaflor, although there was evidence of reduced sensitivity to neonicotinoids and sulfoxaflor, which may be a pre-cursor to resistance.
- In contrast, continued strong resistance to pyrethroids was seen in many of the M. persicae samples.
- These findings were backed up by DNA tests showing that M. persicae carrying the new form (north European: Ne) of super-kdr (conferring resistance to pyrethroids) continue to be common and widespread in the UK with them being found in 71% in the 2021 samples. Interestingly, the other mechanism, kdr, conferring moderate resistance, was also found only in the heterozygous form and was present 24% of the samples. Both resistance frequencies are similar to that seen in 2020.
