An official website of the United States government
Abstract Most pesticide research has focussed on risk to managed honeybees, but other managed and wild bees are also exposed to pesticides. Critically, we know little about the magnitude and sources of risk to honeybees compared with other bees during crop pollination.To compare pesticide exposure and risk across wild and managed bees, we sampled the main bee groups present during bloom in 20 apple orchards, including managed honeybees (Apis mellifera), managed bumblebee workers (Bombus impatiens), wild mining bees (Andrenaspp. andAndrena [Melandrena]spp.), bumblebee foundress queens (Bombus impatiens) and eastern carpenter bees (Xylocopa virginica). We screened all bees for 92 pesticides and computed a Risk Quotient using available toxicity data (honeybee LD50s), adjusting for differences in toxicity known to scale with body mass. To gain insight into exposure origin, we compared residues in bees to those in focal orchard apple and dandelion flowers.Nearly all bee samples contained pesticides (95%), with the average contamination level ranging from 7.1 ± 2.8 parts per billion (ppb) inB. impatiensworkers to 388.4 ± 146.2 ppb inAndrena. Exposure profiles were similar for all bees exceptA. mellifera, whose unique exposure profile included high levels of the neonicotinoid insecticide thiamethoxam.All bee groups except wildB. impatiensqueens had at least one sample exceeding a US Environmental Protection Agency or European Food Safety Authority exposure level of concern.Apis melliferaexperienced significantly greater risk than other bee groups, with 63% and 81% of samples exceeding an acute or chronic exposure level of concern, respectively. Risk to honeybees was driven primarily by high thiamethoxam levels not found in focal orchard flowers and likely originating outside the orchard.Synthesis and applications: We find that pesticide exposure and risk differ between honeybees and other managed and wild bees during apple pollination. Furthermore, pesticide exposure is a landscape‐scale phenomenon and therefore measures to reduce exposure must consider the surroundings beyond focal farms. Limiting orchard sprays, while reducing on‐farm exposures, will not protect far‐foraging bees from off‐farm exposures such as thiamethoxam, which we hypothesize is coming from nearby seed‐treated corn fields planted during apple bloom.
more »
« less
Parasites and pesticides act antagonistically on honey bee health
Abstract Pesticides and parasites have each been linked to increased mortality in western honey bees (Apis mellifera). Currently, it is uncertain if one makes the other worse; several studies have tested for potential synergistic stressor effects, but results have been mixed.Here, we use a hierarchical meta‐analysis of 63 experiments from 26 studies to gain a clearer view of the combined effects of parasites and pesticides on honey bee health.We found that combined pesticide–parasite treatments do tend to be deadlier than uncombined treatments but are significantly less deadly than predicted additive or multiplicative effects. In other words, combined treatment effects are not synergistic, but antagonistic.Much of the previous uncertainty about the combined effects of pesticides and parasites on honey bee health can be attributed to a bias in the previous research against stressor antagonism; many researchers have excluded the possibility of antagonism a priori.Synthesis and applications. Meta‐analysis shows that when honey bees are stressed by a combination of pesticides and parasites, the combined stress effect is antagonistic, that is, less than the sum of its parts. A better understanding of the mechanisms underlying this antagonism could prove critical for effective management of honey bee health.
more »
« less
- Award ID(s):
- 1744552
- PAR ID:
- 10435724
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Applied Ecology
- Volume:
- 58
- Issue:
- 5
- ISSN:
- 0021-8901
- Page Range / eLocation ID:
- p. 997-1005
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Honey bees are critical pollinators in ecosystems and agriculture, but their numbers have significantly declined. Declines in pollinator populations are thought to be due to multiple factors including habitat loss, climate change, increased vulnerability to disease and parasites, and pesticide use. Neonicotinoid pesticides are agonists of insect nicotinic cholinergic receptors, and sub-lethal exposures are linked to reduced honey bee hive survival. Honey bees are highly dependent on circadian clocks to regulate critical behaviors, such as foraging orientation and navigation, time-memory for food sources, sleep, and learning/memory processes. Because circadian clock neurons in insects receive light input through cholinergic signaling we tested for effects of neonicotinoids on honey bee circadian rhythms and sleep. Neonicotinoid ingestion by feeding over several days results in neonicotinoid accumulation in the bee brain, disrupts circadian rhythmicity in many individual bees, shifts the timing of behavioral circadian rhythms in bees that remain rhythmic, and impairs sleep. Neonicotinoids and light input act synergistically to disrupt bee circadian behavior, and neonicotinoids directly stimulate wake-promoting clock neurons in the fruit fly brain. Neonicotinoids disrupt honey bee circadian rhythms and sleep, likely by aberrant stimulation of clock neurons, to potentially impair honey bee navigation, time-memory, and social communication.more » « less
-
Summary A fewCapsicum(pepper) species produce yellow‐colored floral nectar, but the chemical identity and biological function of the yellow pigment are unknown.A combination of analytical biochemistry techniques was used to identify the pigment that givesCapsicum baccatumandCapsicum pubescensnectars their yellow color. Microbial growth assays, visual modeling, and honey bee preference tests for artificial nectars containing riboflavin were used to assess potential biological roles for the nectar pigment.High concentrations of riboflavin (vitamin B2) give the nectars their intense yellow color. Nectars containing riboflavin generate reactive oxygen species when exposed to light and reduce microbial growth. Visual modeling also indicates that the yellow color is highly conspicuous to bees within the context of the flower. Lastly, field experiments demonstrate that honey bees prefer artificial nectars containing riboflavin.SomeCapsicumnectars contain a yellow‐colored vitamin that appears to play roles in (1) limiting microbial growth, (2) the visual attraction of bees, and (3) as a reward to nectar‐feeding flower visitors (potential pollinators), which is especially interesting since riboflavin is an essential nutrient for brood rearing in insects. These results cumulatively suggest that the riboflavin found in someCapsicumnectars has several functions.more » « less
-
Summary Plants naturally harbor diverse microbiomes that can dramatically impact their health and productivity. However, it remains unclear how fungal microbiome diversity, especially in the phyllosphere, impacts intermicrobial interactions and consequent nonadditive effects on plant productivity.Combining manipulative experiments, field collections, culturing, microbiome sequencing, and synthetic consortia, we experimentally tested for the first time how foliar fungal community diversity impacts plant productivity. We inoculated morning glories (Ipomoea hederifoliaL.) with 32 phyllosphere consortia of either low or high diversity or with single fungal taxa, and measured effects on plant productivity and allocation.We found the following: (1) nonadditive effects were pervasive with 56% of fungal consortia interacting synergistically or antagonistically to impact plant productivity, including some consortia capable of generating acute synergism (e.g. > 1000% increase in productivity above the additive expectation), (2) interactions among ‘commensal’ fungi were responsible for this nonadditivity in diverse consortia, (3) synergistic interactions were approximately four times stronger than antagonistic effects, (4) fungal diversity affected the magnitude but not frequency or direction of nonadditivity, and (5) diversity affected plant performance nonlinearly with the highest performance in low‐diversity treatments.These findings highlight the importance of interpreting plant–microbiome interactions under a framework that incorporates intermicrobial interactions and nonadditive outcomes to understand natural complexity.more » « less
-
Abstract Over the last quarter century, increasing honey bee colony losses motivated standardized large-scale surveys of managed honey bees (Apis mellifera), particularly in Europe and the United States. Here we present the first large-scale standardized survey of colony losses of managed honey bees and stingless bees across Latin America. Overall, 1736 beekeepers and 165 meliponiculturists participated in the 2-year survey (2016–2017 and 2017–2018). On average, 30.4% of honey bee colonies and 39.6% of stingless bee colonies were lost per year across the region. Summer losses were higher than winter losses in stingless bees (30.9% and 22.2%, respectively) but not in honey bees (18.8% and 20.6%, respectively). Colony loss increased with operation size during the summer in both honey bees and stingless bees and decreased with operation size during the winter in stingless bees. Furthermore, losses differed significantly between countries and across years for both beekeepers and meliponiculturists. Overall, winter losses of honey bee colonies in Latin America (20.6%) position this region between Europe (12.5%) and the United States (40.4%). These results highlight the magnitude of bee colony losses occurring in the region and suggest difficulties in maintaining overall colony health and economic survival for beekeepers and meliponiculturists.more » « less
