Combating resistance to insecticides in aphid pests of potatoes

AHDB Potatoes supported a series of industry co-funded projects to investigate insecticide resistance in key aphid pests. The majority of the work was focussed on the peach-potato aphid (Myzus persicae). This is an important vector of viruses in potato crops.

LK0903 Combating insecticide resistance in peach-potato aphids in the UK (1997-2000)

The project focussed on the insecticide resistance mechanisms that were established at that time (esterase resistance and knock-down resistance (kdr) conferring resistance to pyrethroids). A second related form of knock-down resistance, known as super-kdr, was isolated in a M. persicae clone in 1997.  It was shown to be associated with high resistance to several pyrethroids. The project also included preliminary work on neonicotinoids. Samples collected in the project were  used to screen for any evidence of reduced sesnitivity to imidacloprid. The results were used to strengthen insecticide usage recommendations at a time when neonictinoids were being used to control M. persicae across an increasing number of crops.

R250 Stewardship of neonicotinoid insecticides (2004-2007)

The project built on the findings from the previous work. It involved detailed characterisation of M. persicae clones that showed reduced sensitivity to imidacloprid and monitoring for variation in sensitivity to the active in samples collected from crops with contrasting levels of neonicotinoid use and dosage. Laboratory studies were used to assess how operational factors (dose, route of exposure) affected resistance selection pressure. 

247 M. persicae samples collected from a range of field and glasshouse crops in England between September 2004 and December 2007 were screened for the presence of Nic-R aphids. There was neither an upward trend with collection date in their frequency nor the presence of any individuals with significantly greater resistance (Nic-R+).  The frequency of M. persicae with high carboxylesterase resistance declined but those with the MACE and kdr mechanisms (to pirimicarb and pyrethroids, respectively) were present in over 50% of the samples collected.

R420 Sustaining the effectiveness of new insecticides against aphid pests in the UK (2009-2012)

The overall aim of the project was to gain a clearer understanding of the incidence of insecticide resistance in several aphid pests (M. persicae, the potato aphid, Macrosiphum euphorbiae, and the currant-lettuce aphid, Nasonovia ribisnigri). The project continued the earlier work monitoring the occurrence and practical implications of resistance to older insecticides in aphids collected from field and protected crops. For newer compounds it established or strengthened bioassays for detailed characterisation of aphid samples. No evidence of significant resistance (that may compromise control) to neonicotinoids, pymetrozine or flonicamid were recorded in M. persicae during the study. 

Laboratory studies with M. persicae clones with strong resistance to imidacloprid (Nic-R++, obtained from overseas), showed there was no apparent fitness cost, measured by ability to respond to aphid alarm pheromone, associated with neonicotinoid resistance. There were also no differences in the ability of M. persicae carrying different levels of neonicotinoid resistance to reproduce at low temperatures (down to -4˚C). Further work on the effect of operational factors on resistance development suggested that the method of treatment will affect the intensity of selection and how resistance is expressed (‘resistance risk’) - with neonicotinoid spray applications imposing greater selection pressures on resistant aphids compared to seed or soil treatments.

Aim: To monitor the response of field-collected live samples of Myzus persicae  to a range of insecticides and also monitor for established forms of resistance