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.
Latest Report
Outcomes / Key Message For Growers And Industry
• Screening of peach-potato aphid (M. persicae) samples taken from the field and protected crops in 2018 showed that there continues to be no significant resistance (that may compromise control) to a range of compounds belonging to different chemical classes (cyantraniliprole, flonicamid, pymetrozine, spirotetramat and sulfoxaflor). Furthermore, there have been no significant shifts in response to diagnostic doses of these insecticides that are currently effective (un-resisted) in GB.
• Strong pirimicarb resistance and pyrethroid resistance (conferred by MACE and super-kdr target site mechanisms respectively), remain prevalent in the M. persicae samples although there is evidence for some changes in the genetic make-up of the GB population with aphids carrying kdr alone becoming more common.
• Microsatelitte analysis of M. persicae populations (an ‘in-kind’ contribution to the project) shows that the ‘O’ and ‘P’ super-clones seem to be on the wain with new genotypes, particularly ‘W’ (which also carries MACE and super-kdr), becoming prevalent.
• Our findings continue to suggest that at least some M. persicae collected from protected crops may have come from more genetically-diverse, sexual populations on imported plant material. Obtaining samples from these environments remains very important as they are more likely to harbour aphids with new resistance mechanisms (e.g. to neonicotinoids) coming into the UK from abroad.
