The effects of a common agricultural fungicide on carbohydrate absorption in honey bees (Apis mellifera)

Post-ingestive feedback mechanisms signal the nutritional value of a food and can determine how well an animal learns about an associated stimulus. In honey bees, during a common associative learning assay in which individuals learn to associate an odor with a sugar reward, bees do not remember the association as well when they are allowed to taste, but not feed on, the sugar. We have previously shown that a common agricultural fungicide, Pristine^® (active ingredients: 25.2% boscalid, 12.8% pyraclostrobin), impairs performance in this olfactory associative learning task. As the active ingredients of Pristine^® are not designed to be neuroactive and instead target the basic biochemical processes of fungal cells, the mechanisms underlying its effects on associative learning performance in honey bees remain unknown. In this presentation, we demonstrate that Pristine^® interferes with carbohydrate absorption in the honey bee gut. Since the post-ingestive feedback mechanisms that aid in associative learning require glucose levels to rise in the hemolymph, we hypothesize that this impaired carbohydrate absorption is the mechanism underlying Pristine^®’s effects on associative learning. Our results advance the understanding of the physiological mechanisms that are responsible for Pristine^®’s negative effects on honey bees and have the potential to influence fungicide safety and usage regulations.