Safety and Sublethal Effects of Acaricides on Stethorus punctillum, a Neglected Key Natural Enemy of Phytophagous Mites

<i>Stethorus punctillum</i> Weise, a predatory beetle attacking phytophagous mites in northwest China, remains underutilized for biological control. Current over-reliance on synthetic acaricides necessitates evaluation of their non-target effects on this predator, particularly their safety and sublethal impacts. Here, we assessed the acute toxicity of four acaricides to <i>S. punctillum</i> in laboratory bioassays and then focused on sublethal impacts of abamectin on adult predation efficiency and lifespan. Based on the LC₅₀ values, the acute toxicities of the four acaricides tested against <i>S. punctillum</i> larvae and adults both ranked as follows (from greatest to least): abamectin > pyridaben > spirotetramat > petroleum oil. All acaricides exhibited selective toxicity (STR: 2.16-182.49) with moderate to low risk (SF: 0.46-8.71). Notably, petroleum oil, despite showing the lowest acute toxicity to <i>S. punctillum</i>, posed the highest risk to larvae (SF: 0.46-0.77). Abamectin exposures at LC₂₀ or LC₅₀ significantly compromised <i>S. punctillum</i> adults, prolonging prey handling time (females: 33-100%; males: 40%), reducing maximum daily predation (females: 25-50%; males: 29%), and shortening adult lifespan (females: 2.34-3.17 days; males: 3.95-5.08 days). This study assessed the safety of four commonly used acaricides for <i>S. punctillum</i>, revealing abamectin-induced impairments to key biological traits. Our findings offer critical insights for risk-aware acaricide selection and integrated spider mite management strategies in agroecosystems in northwest China.