Abstract
Recent work demonstrated that honey bee (Apis mellifera L.) queens reared in pesticide-laden beeswax exhibit significant changes in the composition of the chemicals produced by their mandibular glands including those that comprise queen mandibular pheromone, which is a critical signal used in mating as well as queen tending behavior. For the present study, we hypothesized that pesticide exposure during development would alter other queen-produced chemicals, including brood pheromone in immature queens, thus resulting in differential feeding of queen larvae by nurse workers, ultimately impacting adult queen morphology. We tested these hypotheses by rearing queens in beeswax containing field-relevant concentrations of (1) a combination of tau-fluvalinate and coumaphos, (2) amitraz, or (3) a combination of chlorothalonil and chlorpyrifos. These pesticides are ubiquitous in most commercial beekeeping operations in North America. We observed nurse feeding rates of queen larvae grafted into pesticide-laden beeswax, analyzed the chemical composition of larval queen pheromones and measured morphological markers in adult queens. Neither the nurse feeding rates, nor the chemical profiles of immature queen pheromones, differed significantly between queens reared in pesticide-laden wax compared to queens reared in pesticide-free wax. Moreover, pesticide exposure during development did not cause virgin or mated adult queens to exhibit differences in morphological markers (i.e., body weight, head width, or thorax width). These results were unexpected given our previous research and indicate that future work is needed to fully understand how pesticide exposure during development affects honey bee queen physiology, as well as how various adult queen quality metrics relate to each other.
Highlights
Pesticide contamination is ubiquitous in honey bee colonies across the United States A comprehensive survey conducted a decade ago found that 98.4% of wax samples collected from commercial beekeeping operations in North America were contaminated with multiple pesticides (Mullin et al, 2010)
We examined whether exposure to wax contaminated with field-relevant concentrations of taufluvalinate, coumaphos, amitraz, chlorpyrifos and chlorothalonil during development affected the rate at which queen larvae are fed by nurse bees, their brood pheromone chemical composition and the morphology of emerged virgin and mature queens exposed to these chemicals during development
Queen larvae reared in wax containing taufluvalinate and coumaphos had an average of 5.05 ± 0.01 nurse visits per 5-min interval, larvae reared in amitraz-laden wax had 4.14 ± 0.71 nurse visits per 5-min interval and those reared in wax containing chlorothalonil and chlorpyrifos had 4.71 ± 0.80 nurse visits per 5-min interval
Summary
Pesticide contamination is ubiquitous in honey bee colonies across the United States A comprehensive survey conducted a decade ago found that 98.4% of wax samples collected from commercial beekeeping operations in North America were contaminated with multiple pesticides (Mullin et al, 2010). A more recently introduced miticide, amitraz, and its metabolites N-(2,4-dimethylphenyl)-N-methylformamidine (DMPF) and 2,4-dimethylaniline (DMA), were present in 60.5% of the wax samples analyzed by Mullin et al (2010). In addition to these miticides, two agrochemicals, the fungicide chlorothalonil and the insecticide chlorpyrifos, were among the top five pesticides detected in beeswax samples (Mullin et al, 2010). They were found in 49.2 and 63.2% of all samples analyzed, respectively, and were likely introduced into the colonies by forager bees that visited crops that had been treated with those chemicals. More recent studies have confirmed that wax and other hive products are consistently being exposed to taufluvalinate, coumaphos and amitraz (and its metabolites), in addition to other agro-chemicals (Traynor et al, 2016, 2021a,b; Ostiguy et al, 2019; Milone et al, 2021)
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