Abstract
Honey bee queen health is crucial for colony health and productivity, and pesticides have been previously associated with queen loss and premature supersedure. Prior research has investigated the effects of indirect pesticide exposure on queens via workers, as well as direct effects on queens during development. However, as adults, queens are in constant contact with wax as they walk on comb and lay eggs; therefore, direct pesticide contact with adult queens is a relevant but seldom investigated exposure route. Here, we conducted laboratory and field experiments to investigate the impacts of topical pesticide exposure on adult queens. We tested six pesticides commonly found in wax: coumaphos, tau-fluvalinate, atrazine, 2,4-DMPF, chlorpyriphos, chlorothalonil, and a cocktail of all six, each administered at 1, 4, 8, 16, and 32 times the concentrations typically found in wax. We found no effect of any treatment on queen mass, sperm viability, or fat body protein expression. In a field trial testing queen topical exposure of a pesticide cocktail, we found no impact on egg-laying pattern, queen mass, emergence mass of daughter workers, and no proteins in the spermathecal fluid were differentially expressed. These experiments consistently show that pesticides commonly found in wax have no direct impact on queen performance, reproduction, or quality metrics at the doses tested. We suggest that previously reported associations between high levels of pesticide residues in wax and queen failure are most likely driven by indirect effects of worker exposure (either through wax or other hive products) on queen care or queen perception.
Highlights
Honey bee queen health is crucial for colony health and productivity, and pesticides have been previously associated with queen loss and premature supersedure
Previous research has shown that the presence of a realistic pesticide cocktail in the wax of queen rearing cups had no discernable effect on queen biology; bees in colonies fed pollen containing field-realistic levels of pesticides present in bee bread produce less royal jelly and are less able to rear queens compared to untreated colonies[11,21]
In order to test if topical exposures of different pesticides commonly found in wax affected queen quality metrics, we exposed queens to varying doses of six pesticides as well as a complete cocktail, measured queen mass, sperm viability, as well as other morphometrics associated with reproductive quality
Summary
Honey bee queen health is crucial for colony health and productivity, and pesticides have been previously associated with queen loss and premature supersedure. In a field trial testing queen topical exposure of a pesticide cocktail, we found no impact on egg-laying pattern, queen mass, emergence mass of daughter workers, and no proteins in the spermathecal fluid were differentially expressed. These experiments consistently show that pesticides commonly found in wax have no direct impact on queen performance, reproduction, or quality metrics at the doses tested. Beeswax from commercial honey bee colonies may contain a large number of chemical residues, some at high concentrations.
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