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Willis, Caitlin Emily (2021) Investigating insecticide resistance in UK populations of the cabbage stem flea beetle, Psylliodes chrysocephala. PhD thesis, University of Gloucestershire. doi:10.46289/ZVCY9016
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Text (Final thesis (© Caitlin Emily Willis 2021))
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Abstract
The cabbage stem flea beetle, Psylliodes chrysocephala, is a major pest of winter oilseed rape (OSR), particularly in the UK. Prior to December 2013, control of P. chrysocephala relied on the protection of OSR seedlings by neonicotinoid seed treatments, followed by the application of foliar pyrethroid sprays. However, in 2018, the EU-imposed a ban on the neonicotinoid seed treatments leaving just pyrethroid sprays for P. chrysocephala control. The increased selection pressure, caused by a lack of alternative control agents with different modes of action, has led to the emergence of pyrethroid resistance in this pest, resulting in widely reported control problems. P. chrysocephala adult samples sourced from across the UK in 2018, 2019 and 2020 were found to exhibit high levels of resistance to lambda-cyhalothrin, with the mean resistance level increasing across the three years of monitoring. The target-site mutation L1014F, previously shown to contribute to pyrethroid resistance in samples of P. chrysocephala, was present across most of the samples tested; the L925I mutation was also present in some of the samples. Synergist bioassays found that pyrethroid resistance was suppressed in P. chrysocephala samples pre-treated with PBO, suggesting the presence of a metabolic-based mechanism for resistance. RNA sequencing data from susceptible and resistant samples of P. chrysocephala was analysed and the cytochrome P450 CYP6k1-like identified as the most differentially expressed gene, with qPCR analysis showing that CYP6k1-like was significantly overexpressed in UK resistant samples. Delivery of in vitro synthesised dsRNA by both microinjection and oral delivery caused a knockdown effect of CYP6k1-like. After glass vial bioassays, mortality was significantly higher in the P. chrysocephala injected with in vitro synthesised dsCYP6K1-like relative to those injected with dsGFP suggesting the involvement of CYP6k1-like in conferring resistance to pyrethroids in P. chrysocephala adults. Glass vial bioassays used to evaluate the efficacy of alternative insecticides against pyrethroid resistant P. chrysocephala adults and larvae identified cyantraniliprole as the most toxic compound against P. chrysocephala adults. Cyantraniliprole was also effective against eight P. chrysocephala samples collected across England, suggesting its potential in future control strategies. Of the compounds tested against P. chrysocephala larvae, acetamiprid and fipronil were identified as the most toxic.
| Item Type: | Thesis (PhD) | ||||||||||||||||||
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| Additional Information: | Award conferred by the University of Gloucestershire in partnership with the Royal Agricultural University. | ||||||||||||||||||
| Subjects: | Q Science > QL Zoology > QL360 Invertebrates > QL 461 Insects S Agriculture > SB Plant culture > SB599 Pests and diseases |
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| Divisions: | Schools and Research Institutes > School of Education, Health and Sciences | ||||||||||||||||||
| Depositing User: | Rhiannon Goodland | ||||||||||||||||||
| Date Deposited: | 14 Sep 2026 12:23 | ||||||||||||||||||
| Last Modified: | 14 Sep 2026 12:23 | ||||||||||||||||||
| URI: | https://eprints.glos.ac.uk/id/eprint/16522 |
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