Abstract
Honey bees (Apis mellifera) contribute an estimated $200 billion annually to the global economy, primarily through crop pollination. Despite their importance, the number of managed honey bee colonies continues to decline. Recent surveys have shown that colony losses are attributed in great part to problems associated with the ectoparasitic mite Varroa destructor, and with issues related to poor queen quality (particularly premature queen replacement), which often result in decreased colony productivity and increased risk of mortality. We aimed to investigate how sublethal exposure to beekeeper-applied miticides affects honey bees at both the individual (queen) and colony levels. We did so by comparing the growth (comb built, brood produced, food stored, and worker population), queen supersedure rates, and winter survival probabilities of colonies that were headed by queens that were raised in either miticide-laden or miticide-free beeswax cups then housed in hives that were either treated with miticides or left untreated. Contrary to our prediction, we found that treated colonies headed by queens raised in miticide-laden beeswax built significantly more worker and drone comb, and stored more food, than any other colony treatment. We did not, however, observe any other significant effect of colony treatment on the amount of brood production, worker population size, queen supersedure rate, or colony winter survival. Thus, we failed to observe a direct negative effect of miticide exposure at the colony level. More studies are needed to further test the potentially detrimental synergistic effects of in-hive miticides on honey bee health at the colony level.
Highlights
Pollinator health continues to be a topic of major interest worldwide, due to the rapid population decline of both native and managed pollinator species [1,2,3,4,5]
Of the queen cups that got initiated by workers, 34 queens raised in miticide-free beeswax cups, and 26 queens raised in miticide-laden beeswax cups, emerged from their cells and mated successfully
Colonies headed by queens raised in miticide-laden beeswax cups and housed in hives that were treated with miticides constructed on average twice as much worker comb (Figure 1a; F1,40=4.48, P=0.04) and ~10 times more drone comb (Figure 1b; F1,40=8.72, P=0.009), and stored approximately 60 percent more honey and pollen (Figure 1c; F1,16=4.147, P=0.05), compared to any other colony treatment
Summary
Pollinator health continues to be a topic of major interest worldwide, due to the rapid population decline of both native and managed pollinator species [1,2,3,4,5]. The honey bee (Apis mellifera) is arguably the most important insect pollinator of major agricultural crops, contributing an estimated $200 billion to the global economy annually, $17 billion in the United States alone [6,7,8] Despite their importance to agriculture, the number of managed honey bee colonies available for pollination has decreased steeply in the last decade, threatening the production of many bee-dependent crops nationwide [9,10]. This decline has been attributed to the many health issues facing honey bees today-problems caused by pathogens and parasites, the use of in-hive chemicals to treat for these ailments, the exposure of colonies to agricultural pesticides and genetically modified crops during foraging, and poor beekeeping practices [11,12,13]. The combined information from these reports suggests that the increased use of in-hive chemicals to combat Varroa mites has coincided with a general decrease in colony health that may lead to increased colony losses
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