A Compound Fungicide Impairs Cognitive Performance in Honey Bees (Apis mellifera)

TL;DR

A fungicide called Chunmanchun® harms honey bees' ability to sense sugar and remember, which could affect pollination and agriculture.

Contribution

This study reveals the sublethal cognitive effects of Chunmanchun® on honey bees, emphasizing risks to pollinators and agricultural systems.

Findings

Exposure to Chunmanchun® reduced honey bees' sensitivity to sugar solutions.

Bees exposed to the fungicide showed impaired memory retention in olfactory tasks.

Memory deficits were most severe at higher concentrations of the fungicide.

Abstract

This study highlights the concerning impact of the compound fungicide Chunmanchun® on honey bees, which are crucial for pollination in agriculture. The research aimed to assess how different concentrations of this fungicide affect the bees’ sensitivity to sugar and their learning and memory abilities. The results indicated that exposure to Chunmanchun® significantly lowered the bees’ responses to sugar solutions and impaired their ability to learn and memory. Specifically, bees exposed to sublethal and semi-lethal doses of the fungicide struggled with memory tasks hours after exposure. These findings underscore the risks that such agricultural chemicals pose to pollinator health, which is vital for crop productivity. Protecting bees from the harmful effects of fungicides not only supports their health but also ensures the sustainability of agricultural systems and food production. This research serves as an important reminder for farmers and policy-makers to consider the implications of chemical use on pollinators, advocating for practices that protect these essential insects.

Fungicides play a critical role in crop protection, yet their potential threats to pollinator remain a concern. This study investigated the sublethal effects of a commercial fungicide, Chunmanchun® (a suspension-emulsion of 7% propiconazole and 28% carbendazim), on cognitive functions of the honey bee (Apis mellifera). Using the proboscis extension reflex (PER) assay, we evaluated sucrose sensitivity and olfactory learning and memory in workers exposed to the recommended field concentration (PC), along with sublethal (LD10) and semi-lethal (LD50) concentrations. Fungicide exposure significantly reduced sucrose sensitivity across all concentrations tested (0.1%, 1%, and 3%), with the strongest reductions occurring at the LD10 and LD50 levels. While olfactory associative learning was not significantly impaired, memory retention was adversely affected. Bees in the LD50 group showed significantly reduced PER rates at both1 h and 6 h post-training, and LD10 and LD50 groups exhibited significant memory deficits by 1 h and 6 h relative to the control. These results demonstrate that Chunmanchun® impairs both sucrose responsiveness and olfactory memory in honey bees, which may impair foraging efficiency and ultimately affect colony performance. This study highlights a potential ecological risk posed by this fungicide to pollinators in agricultural environments.

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