Acute toxicity and sublethal effects of neonicotinoid insecticides on the predatory ladybird Propylea japonica.

Background

Neonicotinoid insecticides are widely used for pest control, but their impacts on non-target natural enemies remain insufficiently characterized, particularly at sublethal concentrations. The predatory ladybird Propylea japonica is an important biological control agent in agroecosystems. Here, we evaluated the acute toxicity, ecological risk, sublethal and transgenerational effects, and physiological and transcriptomic responses of P. japonica to multiple neonicotinoid insecticides.

Results

Seven neonicotinoid insecticides showed substantial variation in acute toxicity to second-instar larvae, with LC50 values ranging from 5.82 to 164.70 mg a.i. L-1. Risk assessment based on safety factors indicated that all tested insecticides posed moderate to high ecological risks under field-relevant exposure scenarios. Sublethal exposure to five insecticides markedly impaired parental reproduction, reducing fecundity by 45.5-71.8% and shifting the sex ratio towards males by 19.3-35.1%. Mechanistically, reproductive impairment was associated with disrupted ovarian development, including reduced ovariole number and defective vitellogenesis. Transcriptomic profiling further revealed widespread metabolic reprogramming, characterized by enrichment of xenobiotic metabolism pathways and induction of detoxification gene families. By contrast, transgenerational effects in the F1 generation were relatively limited, mainly involving modest reductions in egg hatchability and slight prolongation of embryonic duration.

Conclusion

Acute toxicity assessment showed that seven neonicotinoid insecticides posed moderate to high ecological risks to P. japonica, while sublethal assays with five selected insecticides revealed substantial reproductive impairment, highlighting the need for more selective use of neonicotinoids to safeguard beneficial predators in agroecosystems. © 2026 Society of Chemical Industry.