The novel insecticides flupyradifurone and sulfoxaflor do not act synergistically with viral pathogens in reducing honey bee (Apis mellifera) survival but sulfoxaflor modulates host immunocompetence

Abstract

The decline of insect pollinators threatens global food security. A major potential cause of decline is considered to be the interaction between environmental stressors, particularly between exposure to pesticides and pathogens. To explore pesticidepathogen interactions in an important pollinator insect, the honey bee, we used two new nicotinic acetylcholine receptor agonist insecticides (nACHRs), flupyradifurone (FPF) and sulfoxaflor (SULF), at sublethal and field-realistic doses in a fully crossed experimental design with three common viral honey bee pathogens, Black queen cell virus (BQCV) and Deformed wing virus (DWV) genotypes A and B. Through laboratory experiments in which treatments were administered singly or in combination to individual insects, we recorded harmful effects of FPF and pathogens on honey bee survival and immune gene expression. Though we found no evidence of synergistic interactions among stressors on either honey bee survival or viral load, the combined treatment SULF and DWV-B led to a synergistic upregulation of dicer-like gene expression. We conclude that common viral pathogens pose a major threat to honey bees, while co-exposure to these novel nACHR insecticides does not significantly exacerbate viral impacts on host survival in the laboratory.

Delayed effects of a single dose of a neurotoxic pesticide (sulfoxaflor) on honeybee foraging activity

“…An increase in oxidative stress and cell apoptosis, as well as a modification of immunocompetence, have been described upon sublethal exposure to sulfoxaflor (Chakrabarti et al 2020;Al Naggar and Paxton 2021;Li et al 2021). However, the behavioral impairments we observed are more in line with an impact on bee cognition.…”

Epidemiology of a major honey bee pathogen, deformed wing virus: potential worldwide replacement of genotype A by genotype B

“…DWV-B was subsequently found to exhibit higher virulence in laboratory experiments with adult honey bees, likely due to the faster rate of replication of DWV-B over DWV-A and the higher titres that DWV-B reached over DWV-A before adult mortality ( McMahon et al, 2016 ). Subsequent experimental comparison of the virulence of DWV-A versus DWV-B ( Tehel et al, 2020 ; Al Naggar and Paxton, 2021 ) have supported the initial demonstration of higher virulence and viral loads reached by DWV-B over DWV-A in adult honey bees. However, these experiments need to be repeated by other research groups to gauge whether they are applicable across isolates of DWV genotypes, subspecies of honey bee and climatic zones.…”

Exposure to Temperature and Insecticides Modulates the Expression of Small Noncoding RNA-Associated Transcripts in the Colorado Potato Beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

“…Honeybees treated with the neonicotinoid thiamethoxam for the same duration displayed varying levels of seven miRNAs when compared with control insects ( Shi et al 2017 ). Honeybees exposed to the insecticide sulfoxaflor in combination with select pathogens displayed increases in Dicer-like gene expression ( Al Naggar and Paxton 2021 ). Modulation of miRNAs in response to insecticides is also observed in L. decemlineata .…”