Pollinator Health Research Articles

Adjuvants for Drone-Based Aerial Chemical Applications to Mitigate Off-Target Drift

Off-target drift from aerial pesticide applications in croplands can be a major source of pesticide exposure to pollinators. Pesticide adjuvants (PAs) are added to pesticides but can be as toxic as pesticides’ active ingredients. Ongoing experiments have identified sodium alginate (SA) as a drift-reducing PA less toxic to honeybees. Hence, SA and fenugreek polymer (FP) have been tested as drift-reducing PAs for aerial applications using the Remotely Piloted Aerial Application System (RPAAS). Two spray experiments were carried out in the field: (i) water only (W) and (ii) water and adjuvant (WA). Droplet spectrum and on-target coverage were collected using a VisiSize P15 image analyzer and kromekote cards, respectively. The drift reduction potentials (DRPs) of the adjuvants were analyzed based on droplet size (diameters of 10%, 50%, and 90% volume) and the proportion of driftable volume with droplets < 200 µm. Compared to the W only, the W-A treatment produced larger droplets, suggesting the presence of DRP. There were 14.5%, 8.3% to 14.4%, and 2.3% to 7.7% driftable fines in the W, WA (SA), and WA (FP) treatments, respectively. The FP treatment improved the on-target coverage (3.0% to 3.1%) compared to water (2.7%). Our results indicate that SA and FP have the potential to mitigate off-target drift and protect pollinator health.

Dying of thirst: Osmoregulation by a hawkmoth pollinator in response to variability in ambient humidity and nectar availability

Climate-induced shifts in flowering phenology can disrupt pollinator-floral resource synchrony, especially in desert ecosystems where rainfall dictates both. However, baseline metrics to gauge pollinator health in the wild amidst rapid climate change are lacking. Our laboratory-based study establishes a baseline for pollinator physiological state by exploring how osmotic conditions influence survivorship in a desert hawkmoth pollinator, Manduca sexta. We sampled hemolymph osmolality from over 1000 lab-grown moths at 20 %, 50 %, and 80 % ambient humidity levels. Starved moths maintained healthy osmolality of 350–400 mmol/kg for 1–3 days after eclosion regardless of ambient humidity, but it sharply rose to 550 mmol/kg after 4–5 days in low and moderate humidity, and after 5 days in high humidity. Starved moths in low humidity conditions perished within 5 days, while those in high humidity survived twice as long. Moths fed synthetic Datura wrightii nectar, synthetic Agave palmeri nectar, or water, maintained osmolality within a healthy range of 350–400mmol/kg. The same was true for moths fed authentic floral nectars from Datura and Agave plants, although moths consumed more synthetic than authentic nectars, possibly due to non-sugar constituents. Simulating a 4-day mismatch between pollinator emergence and nectar availability, a single nectar meal osmotically rescued moths under dry ambient conditions. Our findings highlight hemolymph osmolality as a rapid and accurate biomarker distinguishing dehydrated from hydrated states in insect pollinators.

One-step genome engineering in bee gut bacterial symbionts.

Honey bees are ecologically and economically important crop pollinators with bacterial gut symbionts that influence their health. Microbiome-based strategies for studying or improving bee health have utilized wild-type or plasmid-engineered bacteria. We demonstrate that a straightforward, single-step method can be used to insert cassettes and replace genes in the chromosomes of multiple bee gut bacteria. This method can be used for investigating the mechanisms of host-microbe interactions in the bee gut community and stably engineering symbionts that benefit pollinator health.

Nutrition, pesticide exposure, and virus infection interact to produce context-dependent effects in honey bees (Apis mellifera)

Declines in pollinator health are frequently hypothesized to be the combined result of multiple interacting biotic and abiotic stressors; namely, nutritional limitations, pesticide exposure, and infection with pathogens and parasites. Despite this hypothesis, most studies examining stressor interactions have been constrained to two concurrent factors, limiting our understanding of multi-stressor dynamics. Using honey bees as a model, we addressed this gap by studying how variable diet, field-realistic levels of multiple pesticides, and virus infection interact to affect survival, infection intensity, and immune and detoxification gene expression. Although we found evidence that agrochemical exposure (a field-derived mixture of chlorpyrifos and two fungicides) can exacerbate infection and increase virus-induced mortality, this result was nutritionally-dependent, only occurring when bees were provided artificial pollen. Provisioning with naturally-collected polyfloral pollen inverted the effect, reducing virus-induced mortality and suggesting a hormetic response. To test if the response was pesticide specific, we repeated our experiment with a pyrethroid (lambda-cyhalothrin) and a neonicotinoid (thiamethoxam), finding variable results. Finally, to understand the underpinnings of these effects, we measured viral load and expression of important immune and detoxification genes. Together, our results show that multi-stressor interactions are complex and highly context-dependent, but have great potential to affect bee health and physiology.

Addressing emerging issues in entomology: 2023 student debates.

The Entomological Society of America (ESA) Student Debates is an annual student competition at the ESA Annual Meeting organized by Student Debates Subcommittee (SDS) members of the ESA Student Affairs Committee. In conjunction with the 2023 ESA Annual Meeting theme, 'Insects and influence: Advancing entomology's impact on people and policy', the theme of this year's student debate was 'Addressing emerging issues in entomology'. With the aid of ESA membership, the SDS selected the following debate topics: (1) Should disclosure of artificial intelligence large language models in scientific writing always be required? and (2) Is it more important to prioritize honey bee or native pollinator health for long-term food security within North America? Four student teams from across the nation, composed of 3-5 student members and a professional advisor, were assigned a topic and stance. Over the course of 5 months, all team members researched and prepared for their assigned topic before debating live with an opposing team at the 2023 ESA Annual Meeting in National Harbor, Maryland. SDS members additionally prepared and presented introductions for each debate topic to provide unbiased backgrounds to the judges and audience for context in assessing teams' arguments. The result was an engaging discussion between our teams, judges, and audience members on emerging issues facing entomology and its impact on people and policy, such as scientific communication and food security, that brought attention to the complexities involved when debating topics concerning insects and influence.

Landscape structure affects temporal dynamics in the bumble bee virome: Landscape heterogeneity supports colony resilience

Virus spillovers from managed honey bees, Apis mellifera, are thought to contribute to the decline of wild pollinators, including bumble bees. However, data on the impact of such viruses on wild pollinators remain scarce, and the influence of landscape structure on virus dynamics is poorly understood. In this study, we deployed bumble bee colonies in an agricultural landscape and studied changes in the bumble bee virome during field placement under varying habitat composition and configuration using a multiscale analytical framework. We estimated prevalence of viruses and viral loads (i.e. number of viral genomic equivalent copies) in bumble bees before and after placing them in the field using next generation sequencing and quantitative PCR. The results show that viral loads and number of different viruses present increased during placement in the field and that the virus composition of the colonies shifted from an initial dominance of honey bee associated viruses to a higher number (in both viral loads and number of viruses present) of bumble bee associated viruses. Especially DWV-B, typical for honey bees, drastically decreased after the time in the field. Viral loads prior to placing colonies in the field showed no effect on colony development, suggesting low impacts of these viruses in field settings. Notably, we further demonstrate that increased habitat diversity results in a lower number of different viruses present in Bombus colonies, while colonies in areas with well-connected farmland patches decreased in their total viral load after field placement. Our results emphasize the importance of landscape heterogeneity and connectivity for wild pollinator health and that these influences predominate at fine spatial scales.

Structural and functional impacts of neonicotinoids analogues on Apis mellifera's chemosensory protein: Insights from spectroscopic and molecular modeling investigations

In the intricate web of ecological relationships, pollinators such as the Italian honeybee (Apis mellifera) play a crucial role in maintaining biodiversity and agricultural productivity. This study focuses on the interactions between three neonicotinoid compounds and the honeybee's chemosensory protein 3 (CSP3), a key player in their olfactory system. Employing advanced spectroscopic techniques and molecular modeling, we explore the binding dynamics and conformational changes in CSP3 upon exposure to these pesticides. The research reveals that all three neonicotinoids considerably quench CSP3's fluorescence through a dynamic and static mixing mechanism, indicating a strong binding affinity, predominantly driven by hydrophobic interactions. UV–visible absorption, synchronous fluorescence, and 3D fluorescence spectra support slight changes in the microenvironment around the aromatic amino acids of CSP3. Circular dichroism spectra indicate a reduction in CSP3's α-helix content, suggesting structural alterations. Molecular docking and dynamics simulations further elucidate the binding modes and stability of these interactions, highlighting the role of specific amino acids in CSP3's binding cavity. Findings provide critical insights into molecular mechanisms by which neonicotinoids may impair honeybee chemosensory function, offering implications for designing safer pesticides and understanding the broader ecological impact of these chemicals on pollinator health.

Microbiome and floral associations of a wild bee using biodiversity survey collections.

The health of bees can be assessed through their microbiome, which serves as a biomarker indicating the presence of both beneficial and harmful microorganisms within a bee community. This study presents the characterisation of the bacterial, fungal, and plant composition on the cuticle of adult bicoloured sweat bees (Agapostemon virescens). These bees were collected using various methods such as pan traps, blue vane traps and sweep netting across the northern extent of their habitat range. Non-destructive methods were employed to extract DNA from the whole pinned specimens of these wild bees. Metabarcoding of the 16S rRNA, ITS and rbcL regions was then performed. The study found that the method of collection influenced the detection of certain microbial and plant taxa. Among the collection methods, sweep net samples showed the lowest fungal alpha diversity. However, minor differences in bacterial or fungal beta diversity suggest that no single method is significantly superior to others. Therefore, a combination of techniques can cater to a broader spectrum of microbial detection. The study also revealed regional variations in bacterial, fungal and plant diversity. The core microbiome of A. virescens comprises two bacteria, three fungi and a plant association, all of which are commonly detected in other wild bees. These core microbes remained consistent across different collection methods and locations. Further extensive studies of wild bee microbiomes across various species and landscapes will help uncover crucial relationships between pollinator health and their environment.

Pollinator diversity, pollination services, and conservation in agroecosystems: A mini‐review on the successes and challenges in China

AbstractPollinators provide important pollination services for crops around the world. In China, numerous studies have been conducted on pollinators within agroecosystems, yet a comprehensive review of such research remains to be completed. This study discusses the existing knowledge of pollinator diversity in Chinese agroecosystems, examines the provision of pollination services, and identifies key achievements and limitations. We propose a series of conservation and management actions to promote pollinator health and ecosystem services in these agroecosystems: (1) long‐term monitoring of pollinator populations, (2) designing agricultural landscapes that are conducive to pollinators, and (3) implementing microscale habitat modifications to improve conditions for pollinators.

Unraveling the Impact of Pesticide Exposure on Apis Honey Bees: An Investigation on Succinate Dehydrogenase Subunit A (SDHA) Inhibition Mechanisms

AbstractConcerns about pollinator health and the influence on agricultural ecosystems have developed as a result of pesticide‐caused population declines in honey bees. The research looked at the properties of the SDHA subunit of the enzyme Succinate dehydrogenase, which is important for energy production and mitochondrial function. The goal was to investigate the structural and functional characteristics of SDHA in several Apis bee species, as well as how pesticides can limit its activity. In silico analyses were conducted to understand the structural characteristics of the SDHA subunit, assess evolutionary conservation, analyze deformation energy, and investigate potential pesticide binding. Thirteen pesticides were subjected to molecular docking studies with the Apis SDHA subunit. The study revealed the stability and conserved nature of the SDHA subunit across different Apis sp. Deformation energy analysis highlighted regions of local flexibility, particularly in the active site and interdomain interfaces. Molecular docking analysis indicated that pesticides such as Carboxin, Clothianidin, and Dithianon potentially interfere with FAD binding, while Fipronil and Sulfoxaflor may disrupt both FAD and dicarboxylate binding. This research sheds light on pesticides′ probable inhibitory effects on SDH, a vital enzyme in honey bee energy production and mitochondrial function. The findings highlight the importance of stringent pesticide controls and long‐term pest management measures to protect pollinator numbers and ecosystem health.

Protective covers impact honey bee colony performance and access to outside resources

Protective crop covers are used extensively to protect high-value crops from bird and hail damage, however, these structures may present challenges for honey bees (Apis mellifera L.), the main pollinators in these systems. Some studies have indicated that protective covers result in declines in colony size and resource storage, but few replicated field trials exist. To determine the impact of protective cropping structures on honey bee brood production and resource storage, 14 honey bee colonies were placed inside and outside of protective covers on four blueberry (Vaccinium corymbosum and V. virgatum) farms in northern New South Wales, Australia. We measured changes in brood production, pollen and honey storage, hive weight and ambient hive temperature fortnightly over a 12-week period. Brood production, pollen and honey storage, and hive weight all displayed greater reductions within four weeks of placement under net cover, compared to hives outside of net cover. Although brood and honey metrics gradually increased in all hives during the remainder of the 12-week monitoring period, hives located under protective netting had relatively smaller gains in brood production and pollen storage when compared to hives located outside the protective covering. Hives under protective netting that were in the shade and/or whose entrances were facing south were most impacted by the end of the monitoring period. Our findings highlight the need for protected crop management strategies to consider pollinator health as well as crop pollination needs so that both bee health and pollination services are maintained in these systems.

Landscape fragmentation constrains bumblebee nutritional ecology and foraging dynamics

Habitat fragmentation is modifying landscapes and the distribution of floral resources, possibly shaping pollinator resource acquisition, which is an issue of global concern for pollinator health and urbanization sustainability. Here, in different urban parks contrasting in terms of local features and surrounding urban matrix, we aimed to clarify how fragmentation and local flower availability shape bumblebee foraging dynamics by characterizing several components: the nutritional content and plant composition of collected pollen pellets, the trip length and the plant-nutrition association along a fragmentation gradient. We found mostly negative linear or non-linear relationships between nutritional quality and fragmentation, tight plant composition-nutrition associations interpretable as low access to alternative resources, and longer foraging time in smaller green areas, showing that urban green area fragmentation limits nutritional resource accessibility. However, flower local richness improved the collection of beneficial nutrients as proteins and polyphenols, thus potentially rescuing negative landscape effects. This study illuminates the link between landscape and local features and the nutritional ecology of pollinators, a key aspect for understanding pollinator foraging dynamics. The findings of the study can provide valuable guidelines for policy makers and stakeholders involved in the management and ecological restoration planning for urban green areas and even for outlining mitigation measures in urban contexts.

Genomic and common garden data reveal significant genetic differentiation in the endangered San Fernando Valley spineflower Chorizanthe parryi var. fernandina

San Fernando Valley spineflower (Chorizanthe parryi var. fernandina [S. Watson] Jeps.) (Polygonaceae) is an herbaceous annual plant, endemic to California, and until rediscovered in 1999 had been thought to be extinct for almost seven decades. Historically documented at 10 locations, it currently persists at 2, separated by approximately 27 km. State listed as endangered, a description of its genetic diversity and structure is of conservation interest. After determining a lack of variation in ploidy, we examined genetic variation from samples within both populations: a common garden study for potentially adaptive genetic variation in selected growth and phenological traits and analysis of single nucleotide polymorphisms identified through restriction-site associated DNA sequencing. Both measures indicated that this highly restricted taxon nevertheless harbors substantial levels of genetic diversity and has significant between- and within-population genetic structure. Combining approaches from population genomics and common garden studies provided more insight into the patterns and basis of genetic diversity than is typical for studies of non-model species. Although local adaptation was not specifically studied (i.e., via reciprocal transplant studies), the differences determined from these two independent lines of evidence indicate that mixing gene pools between populations is not recommended at this time. Further, with significant differences revealed among subpopulations, we caution against mixing genotypes across subpopulations for the most part, and without much more evidence that this would not pose a risk of outbreeding depression. The importance of supporting pollinator health and diversity is highlighted. With genetic diversity—particularly with an annual species—being dynamic, fluctuating with the usual processes and with contributions from the soil seedbank, we recommend periodic resampling to monitor genetic diversity and structure. Climate change is anticipated to contribute to this variability.

Bumble bee microbiota shows temporal succession and increase of lactic acid bacteria when exposed to outdoor environments.

The large earth bumble bee (Bombus terrestris) maintains a social core gut-microbiota, similar as known from the honey bee, which plays an important role for host health and resistance. Experiments under laboratory conditions with commercial hives are limited to vertically transmitted microbes and neglect influences of environmental factors or external acquisition of microbes. Various environmental and landscape-level factors may have an impact on the gut-microbiota of pollinating insects, with consequences for pollinator health and fitness in agroecosystems. Still, it is not fully clear whether access to different flower diversities will have a significant influence on the bumble bee microbiota. Here, we tested in a semi-field experiment if the bumble bee microbiota changes over time when exposed to different flower diversities within outdoor flight cages. We used commercial hives to distinguish between vertically and horizontally transmitted bacteria, respectively from the nest environment or the exposed outside environment. The sequential sampling of foraging workers over a period of 35 days indicated a temporal progression of the bumble bee microbiota when placed outside. The microbiota increased in diversity and changed in composition and variability over time. We observed a major increase in relative abundance of the families Lactobacillaceae, Bifidobacteriaceae and Weeksellaceae. In contrast, major core-taxa like Snodgrassella and Gilliamella declined in their relative abundance over time. The genus Lactobacillus showed a high diversity and strain specific turnover, so that only specific ASVs showed an increase over time, while others had a more erratic occurrence pattern. Exposure to different flower diversities had no significant influence on the progression of the bumble bee microbiota. The bumble bee microbiota showed a dynamic temporal succession with distinct compositional changes and diversification over time when placed outdoor. The exposure of bumble bees to environmental conditions, or environmental microbes, increases dissimilarity and changes the gut-community composition. This shows the importance of environmental influences on the temporal dynamic and progression of the bumble bee microbiota.

Land-use affects pollinator-specific resource availability and pollinator foraging behaviour.

Land-use management is a key factor causing pollinator declines in agricultural grasslands. This decline can not only be directly driven by land-use (e.g., habitat loss) but also be indirectly mediated through a reduction in floral resource abundance and diversity, which might in turn affect pollinator health and foraging. We conducted surveys of the abundance of flowering plant species and behavioural observations of two common generalist pollinator species, namely the bumblebee Bombus lapidarius and the syrphid fly Episyrphus balteatus, in managed grasslands of variable land-use intensity (LUI) to investigate whether land-use affects (1) resource availability of the pollinators, (2) their host plant selection and (3) pollinator foraging behaviour. We have found that the floral composition of plant species that were used as resource by the investigated pollinator species depends on land-use intensity and practices such as mowing or grazing. We have also found that bumblebees, but not syrphid flies, visit different plants depending on LUI or management type. Furthermore, LUI indirectly changed pollinator behaviour via a reduction in plot-level flower diversity and abundance. For example, bumblebees show longer flight durations with decreasing flower cover indicating higher energy expenditure when foraging on land-use intensive plots. Syrphid flies were generally less affected by local land use, showing how different pollinator groups can differently react to land-use change. Overall, we show that land-use can change resource composition, abundance and diversity for pollinators, which can in turn affect pollinator foraging behaviour and potentially contribute to pollinator decline in agricultural grasslands.

A quantitative survey of the blueberry (Vaccinium spp.) culturable nectar microbiome: variation between cultivars, locations, and farm management approaches.

Microbes in floral nectar can impact both their host plants and floral visitors, yet little is known about the nectar microbiome of most pollinator-dependent crops. In this study, we examined the abundance and composition of the fungi and bacteria inhabiting Vaccinium spp. nectar, as well as nectar volume and sugar concentrations. We compared wild V. myrsinites with two field-grown V. corymbosum cultivars collected from two organic and two conventional farms. Differences in nectar traits and microbiomes were identified between V. corymbosum cultivars but not Vaccinium species. The microbiome of cultivated plants also varied greatly between farms, whereas management regime had only subtle effects, with higher fungal populations detected under organic management. Nectars were hexose-dominant, and high cell densities were correlated with reduced nectar sugar concentrations. Bacteria were more common than fungi in blueberry nectar, although both were frequently detected and co-occurred more often than would be predicted by chance. "Cosmopolitan" blueberry nectar microbes that were isolated in all plants, including Rosenbergiella sp. and Symmetrospora symmetrica, were identified. This study provides the first systematic report of the blueberry nectar microbiome, which may have important implications for pollinator and crop health.

Bacteriophages: sustainable and effective solution for climate-resilient agriculture

Abstract Climate change entails significant challenges to global food security and agricultural sustainability, prompting the need for innovative solutions to enhance climate resilience in farming practices. Bacteriophages (phages), viruses that specifically target and infect bacteria, provide promising applications in numerous agricultural practices to address these challenges. With traits such as specificity towards bacterial pathogens along with self-replication, self-dosing, and adaptability properties phages offer potential as effective biocontrol agents while exerting minimal harm on non-target organisms or their surrounding environment. In this review, various applications of phages have been explored, including increasing crop resilience, improving soil health, preserving food, managing water resources, and adapting to emerging pests and diseases. Additionally, the benefits of these applications are also explored, such as improving sustainable practices, enhancing plant growth and yield, and supporting pollinator health. Although they offer great promise, there are still several obstacles such as limited host range, environmental stability, and regulatory challenges, so further research and policies are required for their integration into agricultural systems. Furthermore, education and public awareness are essential for farmers to adopt phage-based biocontrol. By harnessing the potential of phages, agriculture can mitigate the adverse effects of climate change, promote sustainability, and ensure food security in a changing climate.

Nutritional profiling of common eastern North American pollen species with implications for bee diet and pollinator health

Nutritional profiling of common eastern North American pollen species with implications for bee diet and pollinator health

Impact of isolated and unattractive crops on honeybee foraging: A case study using radio frequency identification and hybrid carrot seed crops

Abstract Hybrid vegetable varieties have become essential for global agricultural production, offering key advantages for yield, quality and disease resistance. The production of hybrid seeds is however limited by pollination challenges, with these systems commonly associated with unattractive and low‐quality floral resources, isolated growing environments and frequent insecticide applications. Here, we utilise commercial carrot seed crops to investigate the impact of hybrid pollination on the behaviour of the honey bee (Apis mellifera). Six full‐strength bee colonies were equipped with solar powered radio frequency identification systems and over 900 tagged bees per season. These colonies were deployed to commercial hybrid seed crops over two consecutive seasons. The colonies were allocated to either an on‐crop or off‐crop group. Individual bees were autonomously monitored for the pollination period to assess key parameters such as survival, age at foraging and the number and duration of orientation and foraging trips. Hybrid carrots were found to have a significant impact on bee foraging behaviour. Bees situated on the carrot crop undertook less frequent yet longer foraging trips, resulting in less total time outside of the colony compared to off‐crop bees. However, bees placed in carrot fields survived to an older age, orientated successfully, became foragers later and collected more pollen by weight, despite only 2% originating from carrot. We hope that the improved behavioural understanding can be utilised to enhance both pollinator health and hybrid seed production globally.

Efficient degradation of imidacloprid by surface discharge cold plasma: Mechanism of interaction between ROS and molecular structure and evaluation of residual toxicity

Incorrect use of neonicotinoid pesticides poses a serious threat to human and pollinator health, as these substances are commonly present in bee products and even drinking water. To combat this threat, the study developed a new method of degrading the pesticide imidacloprid using surface discharge cold plasma oxidation technology. The study showed that this method achieved a very high efficiency of imidacloprid degradation of 91.4%. The main reactive oxygen species (H2O2, O3, ·OH, O2-, 1O2) effectively participated in the decomposition reaction of imidacloprid. Reactive oxygen species were more sensitive to the structure of the nitroimine group. Density functional theory (DFT) further explored the sites of reactive oxygen species attack on imidacloprid and revealed the process of energy change of attacking imidacloprid. In addition, a degradation pathway for imidacloprid was proposed, mainly involving reactive oxygen species chemisorption, a ring-opening intermediate, and complete cleavage of the nitroimine group structure. Model predictions indicated that acute oral and developmental toxicity were significantly reduced after cold plasma treatment, as confirmed by insect experiments. Animal experiments have shown that plasma treatment reduces imidacloprid damage to mice hippocampal tissue structure and inhibits the reduction of brain-derived neurotrophic factor content, thus revealing the detoxification mechanism of the body.