How do neonicotinoids affect social bees? Linking proximate mechanisms to ecological impacts

Crall, James D.; Raine, Nigel E.

doi:10.1016/bs.aiip.2023.01.004

Cited by 5 publications

(5 citation statements)

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“…positive density dependence, or Allee effects). Colony size and stressor interactions have been separately recognized as critically important for understanding pollinator health [ 56 – 58 ]; here we show that colony size can also modulate interactions between stressors. Smaller colonies also showed higher sensitivity when group size was experimentally manipulated ( figure 6 ), providing strong evidence that group size per se (rather than colony stage, age or development) is an important factor driving these effects.…”

Section: Discussionmentioning

confidence: 59%

Colony size buffers interactions between neonicotinoid exposure and cold stress in bumblebees

et al. 2023

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Social bees are critical for supporting biodiversity, ecosystem function and crop yields globally. Colony size is a key ecological trait predicted to drive sensitivity to environmental stressors and may be especially important for species with annual cycles of sociality, such as bumblebees. However, there is limited empirical evidence assessing the effect of colony size on sensitivity to environmental stressors or the mechanisms underlying these effects. Here, we examine the relationship between colony size and sensitivity to environmental stressors in bumblebees. We exposed colonies at different developmental stages briefly (2 days) to a common neonicotinoid (imidacloprid) and cold stress, while quantifying behaviour of individuals. Combined imidacloprid and cold exposure had stronger effects on both thermoregulatory behaviour and long-term colony growth in small colonies. We find that imidacloprid's effects on behaviour are mediated by body temperature and spatial location within the nest, suggesting that social thermoregulation provides a buffering effect in large colonies. Finally, we demonstrate qualitatively similar effects in size-manipulated microcolonies, suggesting that group size per se , rather than colony age, drives these patterns. Our results provide evidence that colony size is critical in driving sensitivity to stressors and may help elucidate mechanisms underlying the complex and context-specific impacts of pesticide exposure.

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Section: Discussionmentioning

confidence: 59%

Colony size buffers interactions between neonicotinoid exposure and cold stress in bumblebees

et al. 2023

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“…Current knowledge about the effects of pesticides on bees comes from research focused on the consumption of contaminated pollen and nectar by a limited number of eusocial species, namely honeybees (Apis mellifera) and bumblebees (Bombus spp.) [9][10][11]. However, variations in pesticide exposure and sensitivity across bee species, attributed to differences in physiological and life-history traits [12], underscore the necessity of exploring diverse exposure routes to gain a better understanding of the full impacts of pesticides on wild bee communities.…”

Section: Introductionmentioning

confidence: 99%

“…Being highly persistent and systemic insecticides, neonicotinoids commonly contaminate the flower, soil and water resources that bees rely upon [15,[19][20][21]. Sublethal effects of neonicotinoids on bees often manifest in impairment of learning and memory functions, foraging behaviours, motor activity, and orientation and navigation (reviewed in [10,22]). In ground-nesting bees and other wild bees that use soil as a nesting material (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Single and combined exposure to ‘bee safe’ pesticides alter behaviour and offspring production in a ground-nesting solitary bee ( Xenoglossa pruinosa )

Rondeau,

Raine

2024

Proc. R. Soc. B.

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Mounting evidence supporting the negative impacts of exposure to neonicotinoids on bees has prompted the registration of novel ‘bee-friendly’ insecticides for agricultural use. Flupyradifurone (FPF) is a butenolide insecticide that shares the same mode of action as neonicotinoids and has been assessed to be ‘practically non-toxic to adult honeybees' using current risk assessment procedures. However, these assessments overlook some routes of exposure specific to wild bees, such as contact with residues in soil for ground-nesters. Co-exposure with other pesticides may also lead to detrimental synergistic effects. In a fully crossed experiment, we assessed the possible lethal and sublethal effects of chronic exposure to two pesticides used on Cucurbita crops, the insecticide Sivanto Prime (FPF) and the fungicide Quadris Top (azoxystrobin and difenoconazole), alone or combined, on solitary ground-nesting squash bees ( Xenoglossa pruinosa ). Squash bees exposed to Quadris Top collected less pollen per flower visit, while Sivanto-exposed bees produced larger offspring. Pesticide co-exposure induced hyperactivity in female squash bees relative to both the control and single pesticide exposure, and reduced the number of emerging offspring per nest compared to individual pesticide treatments. This study demonstrates that ‘low-toxicity’ pesticides can adversely affect squash bees under field-realistic exposure, alone or in combination.

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“…While agrochemicals (e.g., insecticides, fungicides, herbicides) are typically assessed for safety to insect pollinators based on toxicity testing (i.e., bee mortality), much recent work has shown that exposure to pesticides licensed for use can have negative sublethal effects (Crall et al, 2018;Godfray et al, 2014;Lundin et al, 2015;Siviter & Muth, 2020;Siviter, Richman, & Muth, 2021;Stanley, Smith, & Raine, 2015;Stanley, Garratt, et al 2015;Whitehorn et al, 2012Whitehorn et al, , 2017, including broad effects on behavior. Instead of impacting adult mortality directly, these sublethal effects of pesticide exposure can negatively impact foraging performance, mating success, brood production, and the provisioning of brood cells, and overall colony growth, leading to population-level declines (Boff et al, 2022;Crall & Raine, 2023;Desneux et al, 2007;Gill et al, 2012;Raine & Rundlöf, 2024;Stuligross & Williams, 2021;Willis Chan & Raine, 2021a).…”

Section: Introductionmentioning

confidence: 99%

Field agrochemical exposure impacts locomotor activity in wild bumblebees

Strang,

Rondeau,

Baert

et al. 2024

Ecology

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Agricultural intensification has been identified as one of the key causes of global insect biodiversity losses. These losses have been further linked to the widespread use of agrochemicals associated with modern agricultural practices. Many of these chemicals are known to have negative sublethal effects on commercial pollinators, such as managed honeybees and bumblebees, but less is known about the impacts on wild bees. Laboratory‐based studies with commercial pollinators have consistently shown that pesticide exposure can impact bee behavior, with cascading effects on foraging performance, reproductive success, and pollination services. However, these studies typically assess only one chemical, neglecting the complexity of real‐world exposure to multiple agrochemicals and other stressors. In the summer of 2020, we collected wild‐foraging workers of the common eastern bumblebee, Bombus impatiens, from five squash (Cucurbita) agricultural sites (organic and conventional farms), selected to represent a range of agrochemical, including neonicotinoid insecticide, use. For each bee, we measured two behaviors relevant to foraging success and previously shown to be impacted by pesticide exposure: sucrose responsiveness and locomotor activity. Following behavioral testing, we used liquid chromatography–tandem mass spectrometry (LC–MS/MS) chemical analysis to detect and quantify the presence of 92 agrochemicals in each bumblebee. Bees collected from our sites did not vary in pesticide exposure as expected. While we found a limited occurrence of neonicotinoids, two fungicides (azoxystrobin and difenoconazole) were detected at all sites, and the pesticide synergist piperonyl butoxide (PBO) was present in all 123 bees. We found that bumblebees that contained higher levels of PBO were less active, and this effect was stronger for larger bumblebee workers. While PBO is unlikely to be the direct cause of the reduction in bee activity, it could be an indicator of exposure to pyrethroids and/or other insecticides that we were unable to directly quantify, but which PBO is frequently tank‐mixed with during pesticide applications on crops. We did not find a relationship between agrochemical exposure and bumblebee sucrose responsiveness. To our knowledge, this is the first evidence of a sublethal behavioral impact of agrochemical exposure on wild‐foraging bees.

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How do neonicotinoids affect social bees? Linking proximate mechanisms to ecological impacts

Cited by 5 publications

References 255 publications

Colony size buffers interactions between neonicotinoid exposure and cold stress in bumblebees

Colony size buffers interactions between neonicotinoid exposure and cold stress in bumblebees

Single and combined exposure to ‘bee safe’ pesticides alter behaviour and offspring production in a ground-nesting solitary bee ( Xenoglossa pruinosa )

Field agrochemical exposure impacts locomotor activity in wild bumblebees

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