Can near-infrared exposure help mitigate pesticide-impaired thermoregulation in adult bees?

Abstract Exposure to pesticides may place the process of animal thermo regulation at risk, with impacts on organism fitness and function across landscapes. Quantifying such impacts while finding mitigative solutions is thus important, especially given that pesticide applications are forecast to continue across changing thermal landscapes. Here, we expose an important insect pollinator—bumblebees—to a cholinergic pesticide (neonicotinoid) and characterise the impact on adult body temperature. We further investigate how near infrared (NIR; 660 or 850 nm) mediates this pesticide effect using three exposure durations (5, 10 or 20 min h–1). Held at 18°C ambient, pesticide-only exposed bees exhibited a steep body temperature drop (nearly 8°C) over the 73 h assay (relative to control bees that maintained their body at approx. 30°C). Promisingly, for pesticide- and NIR-exposed bees, 660 nm for 5 min more than halved the rate of body temperature decrease (relative to pesticide-only bees), and intriguingly, this counter-effect lessened with increased NIR exposure time. Additionally, 850 nm for 20 min may also alleviate body temperature decline by nearly 40%. Our study reports a mechanism by which pesticides threaten the critical functioning of a non-target organism and provides a potential therapy worthy of further investigation.