UC San Diego

Honey bees are important pollinators in ecosystems and for agriculture across the world. When they are exposed to neonicotinoid pesticides such as thiamethoxam (TMX), there are significant negative effects even at sublethal doses. Red light exposure may be able to reduce the harmful sublethal effects of pesticides in honey bees. By studying survival over time, phototactic behavior in acutely exposed bees, and using respirometry analysis to track mitochondrial function, this research tested the efficacy of different exposure times of 660 nm red light on bees exposed to varying amounts of the neonicotinoid pesticide thiamethoxam (TMX). Survival assays showed that at a low but field realistic dose of TMX, 5 min of 660 nm red light exposure once per day improved the survival rate of pesticide-exposed bees to the level of comparable bees not exposed to pesticide. Phototaxis assays indicated that at sufficiently high doses, a combination of acute pesticide exposure and 660 nm red light exacerbates the effects of TMX, increasing bee mortality and inducing more severe, deadly response to TMX. Mitochondrial respirometry revealed significant negative effects of the short dose of red light on the function of several functional mitochondrial complexes. These are the first results exploring the specific negative interactions neonicotinoids have on mitochondrial function. Thus, red light can rescue bees exposed to a low dose of TMX, but the combination of the two can also be harmful.