P450‐mediated resistance in Myzus persicae (Sulzer) (Hemiptera: Aphididae) reduces the efficacy of neonicotinoid seed treatments in Brassica napus

Abstract

BACKGROUND: The prophylactic use of seeds treated with neonicotinoid insecticides remains an important means of controlling aphid pests in canola (Brassica napus) crops in many countries. Yet, one of the most economically important aphid species worldwide, the peach potato aphid (Myzus persicae), has evolved mechanisms which confer resistance to neonicotinoids, including amplification of the cytochrome P450 gene, CYP6CY3. While CYP6CY3 amplification has been associated with lowlevel resistance to several neonicotinoids in laboratory acute toxicity bioassays, its impact on insecticide efficacy in the field remains unresolved. In this study, we investigated the impact of CYP6CY3 amplification on the ability of M. persicae to survive neonicotinoid exposure under laboratory and semi-field conditions.RESULTS: Three M. persicae clones, possessing different copy numbers of CYP6CY3, were shown to respond differently when exposed to the neonicotinoids, imidacloprid and thiamethoxam, in laboratory bioassays. Two clones, EastNaernup209 and Osborne171, displayed low levels of resistance (3-20-fold), which is consistent with previous studies. However, in a large-scale semi-field trial, both clones showed a surprising ability to survive and reproduce on B. napus seedlings grown from commercial rates of neonicotinoid-treated seed. In contrast, an insecticide-susceptible clone, of wild-type CYP6CY3 copy number, was unable to survive on seedlings treated in the same manner. CONCLUSION: Our findings suggest that amplification of CYP6CY3 in M. persicae clones substantially impairs the efficacy of neonicotinoid seed treatments when applied to B. napus. These findings highlight the potentially important real-world implications of resistances typically considered to be 'low level' as defined through laboratory bioassays.

Overexpression of an Integument Esterase Gene LbEST-inte4 Infers the Malathion Detoxification in Liposcelis bostrychophila (Psocoptera: Liposcelididae)

“…The upregulation of LbEST-inte4 was not transient but continuous after malathion exposure, and its expression exhibited an upward trend over time. A similar response has also been observed in various insect species, where the induction of specific gene transcript level is associated with insecticide detoxication. − …”

Application of a Mechanistic Model to Explore Management Strategies for Biological Control of an Agricultural Pest

“…Moreover, most canola currently grown in Australia is treated with neonicotinoid-based seed treatments, a control that we have not considered here (other than to interpret the 'delayed aphid arrival' scenario as such). In the context of our model, seed treatments would act to delay the arrival of aphids by up to ten weeks [39], and can impact wasps via several pathways (e.g., wasps developing within aphids, direct contact with the plant, or feeding on tainted plants and/or honeydew [43,44]). Importantly, our model indicates that if insecticide seed treatments in canola become unavailable (or restricted) in the future, there is potential for the greater utility of D. rapae to control M. persicae outbreaks and that using aphid-selective foliar insecticides could support this biological control.…”

“…We calculated the relative change in aphid densities for each of the three management scenarios in comparison to those without any intervention (see above). Insecticide seed treatments are commonplace in Australian canola; however, all registered products with aphid activity rely on neonicotinoids as the main active ingredient [12,36,39]. Given the regulatory pressures facing neonicotinoids globally and the emergence of P450-mediated resistance in Australian M. persicae [39], the future role of insecticide seed treatments is tenuous, and so we excluded these from our study, allowing us to explore alternative scenarios (e.g., the foliar application of chemicals and biological control), where seed treatments were not available.…”

Enthralling genetic regulatory mechanisms meddling insecticide resistance development in insects: role of transcriptional and post-transcriptional events

“…Multiple copies provided higher degrees of resistance, demonstrating the adaptability of the genetic architecture of resistance to organophosphate and carbamate insecticides surrounding the ace-1 locus ( Milesi et al, 2022 ). Because of an increased gene copy number, overexpression of the CYP6CY3 gene gives neonicotinoid resistance in the aphid M. persicae ( Kirkland et al, 2023 ). Copy number variation increased CYP6G1 gene expression in D. melanogaster ( Schmidt et al, 2010 ).…”