Crop Pollination Research Articles

Distinct pollinator communities persist among co-flowering specialty crops in Indiana

Diverse bee communities pollinate fruits and vegetables, and the composition of these communities has been described for many specialty crops in major production regions. However, pollinator communities in landscapes dominated by agronomic crops may differ in species composition and the contribution of wild bees. With over 4 million ha of maize and soybean, Indiana presents a novel landscape to compare pollinator communities among specialty crops that differ in their use of managed bees and bloom phenology, with potential implications for the composition of wild bee communities and their contributions to flower visitation. We sampled pollinator communities with flower observations and pan traps in spring-blooming apples and blueberries and summer-blooming tomatoes and watermelons, allowing us to compare communities between specialty crops with overlapping and distinct bloom times. Apples, blueberries, and watermelons were stocked with honey bees, and watermelons additionally had managed bumble bees. Across two years of sampling, we observed 1,651 flower visits by 13 taxa, collected 1,967 bees, and identified 84 taxa from collected specimens. Apples and blueberries hosted the richest pollinator communities (34 and 51 taxa, respectively) followed by watermelons (22 taxa), and tomatoes (19 taxa). While 70% of flower visits in apples and blueberries were attributed to honey bees, wild bees accounted for 82% and 99% of flower visits in watermelons and tomatoes, respectively. Our results indicate that distinct pollinator communities persist among co-flowering specialty crops in a landscape dominated by maize and soybean production and underscore the contribution of wild bees for specialty crop pollination, particularly in watermelons and tomatoes.

Pollen foraging mediates exposure to dichotomous stressor syndromes in honey bees.

Recent declines in the health of honey bee colonies used for crop pollination pose a considerable threat to global food security. Foraging by honey bee workers represents the primary route of exposure to a plethora of toxins and pathogens known to affect bee health, but it remains unclear how foraging preferences impact colony-level patterns of stressor exposure. Resolving this knowledge gap is crucial for enhancing the health of honey bees and the agricultural systems that rely on them for pollination. To address this, we carried out a national-scale experiment encompassing 456 Canadian honey bee colonies to first characterize pollen foraging preferences in relation to major crops and then explore how foraging behavior influences patterns of stressor exposure. We used a metagenetic approach to quantify honey bee dietary breadth and found that bees display distinct foraging preferences that vary substantially relative to crop type and proximity, and the breadth of foraging interactions can be used to predict the abundance and diversity of stressors a colony is exposed to. Foraging on diverse plant communities was associated with increased exposure to pathogens, while the opposite was associated with increased exposure to xenobiotics. Our work provides the first large-scale empirical evidence that pollen foraging behavior plays an influential role in determining exposure to dichotomous stressor syndromes in honey bees.

Buzzing towards Resilience: Investigating the Spatial Alignment of the Desert Pallid Bee, Centris pallida, and Its Host Plants in Response to Climate Change.

Wild bees are vital for the pollination of native plants and crops, providing essential ecosystem services. Climate change is known to impact biodiversity and species distributions, but insects adapted to desert ecosystems may exhibit unique physiological, behavioral, and evolutionary responses. The desert pallid bee (C. pallida), a solitary bee native to the arid southwestern United States and northern Mexico, primarily forages on yellow palo verde (P. microphylla), blue palo verde (P. florida), and desert ironwood (O. tesota). This study used MaxEnt to estimate the current and projected geographical overlap of suitable habitats for C. pallida and its host plants. Here, we used MaxEnt to estimate the current and forecasted overlapping geographically suitable habitat of C. pallida with all three host plants. We forecasted potential environmentally suitable areas for each species to the year 2040 using the current distribution model and climate projections with moderate CO2 levels. We found a continued spatial alignment in the suitable area of the bee and its host plants with a 70% increase in the range overlap area, though shifted to higher average altitudes and a slight northern expansion. These findings may provide insight to stakeholders on the conservation needs of desert-dwelling pollinators.

Biological invasions threaten crops: Alien Himalayan balsam lures and co-opts floral visitors away from cultivated cherry tomatoes

While it has been demonstrated that invasive alien plants pose a threat to co-occurring wild-growing native plants by attracting their pollinators, we know almost nothing about their impact on crop pollination. Alien plants with attractive flowers sometimes occur close to crops and may influence yields when they share the same pollinators and have overlapping flowering periods. We present the results of an experiment on the impact of alien balsam (Impatiens glandulifera) on the pollination of cherry tomato (Solanum lycopersicum var. cerasiforme). We verified whether balsam decreases the number of insect visits to the tomato flowers or, conversely, whether balsam may have a positive influence on the pollination rate of the crop. We also assessed crop production with and without the insect visitors. The study was conducted in southern Poland under garden and greenhouse experimental conditions simulating small-scale cultivation of the crop with a neighbouring patch of the alien plant. The studied plants were exposed to insects visiting flowers of the following variants: only one of the two species was exposed or both species were exposed together. Moreover, two factors that may influence insect visits in flowers were assessed: the chemical composition of the floral scent that attracts insects and floral pathogens infesting pollinators that may deter them. The number of insect visits (mainly Bombus pascuorum) on the tomato flowers decreased significantly when the plants were exposed to the alien balsam. Moreover, alien balsam secreted more flower attractants (mainly fatty acids and their esters) than tomatoes, which could explain more frequent insect visits in balsam flowers. However, the floral pathogens probably had a negligible impact on the number of insect visits to the flowers of the two plants. The level of infestation on both studied species was relatively low (I. glandulifera: 5.1% of all pathogen colonies grown in a laboratory, S. lycopersicum var. cerasiforme: 4.2% and 2.6% of all colonies in the garden and greenhouse, respectively) and we found no pathogens known to infect pollinators. It should be noted, however, that some of these pathogens (e.g. Botrytis cinerea, Fusarium oxysporum and Sclerotinia sclerotiorum) are known to cause severe diseases in many crops. Our results revealed that the presence of attractive invasive alien species near small-scale cultivations may negatively affect crop pollination, resulting in smaller fruit size and irregular shape. The impact of such alien species on crop production and the agricultural economy on a large scale requires further study.

Wild Bee Conservation in Viticulture: Effects of Semi-Natural Habitats, Organic Management, and Fungicide Reduction.

In agricultural landscapes, the removal of semi-natural habitats (SNH) and the intensive use of pesticides contribute to declines of biodiversity, including crop pollinators such as bees (Hymenoptera: Apoidea). However, effects of pesticide use and landscape characteristics on bees have rarely been studied together. In this study, we investigated how SNH in the surrounding landscape, organic and conventional management, and the reduction of fungicides affect wild bee diversity in 32 vineyards in southwest Germany. We used yellow pan traps to sample bees in a crossed design of management (organic vs. conventional) and fungicide use (reduced in fungus-resistant grape varieties vs. regular) along a gradient with increasing proportions of SNH in the surrounding landscape. Higher proportions of SNH influenced species composition of bees and increased the abundance and richness of above-ground-nesting species. Organic vineyards had a 49% higher abundance of bees compared to conventional vineyards. The reduction of fungicides did not affect bee diversity nor abundance. The absence of a response to fungicide intensity suggests that the benefit of organically managed vineyards to wild bees was through differences in their vegetation management, which is in line with the positive response of bees to SNH in the surrounding landscape. Synthesis and applications: Our study underlines that the local provision of diverse vegetation in vineyards and the landscape-scale provision of suitable SNH are key factors for wild bee conservation in viticulture.

External morphometric and microscopic analysis of the reproductive system in in- vitro reared stingless bee queens, Heterotrigona itama, and their mating frequency.

Stingless bees, prevalent in tropical and subtropical regions, are a tribe of eusocial bees that are crucial pollinators for economic crops and native plants and, produce honey and pollen. However, colony expansion is limited by a shortage of queens for new colonies. Therefore, mass artificial rearing of virgin queens could address this in commercially managed meliponiculture. Furthermore, the in vitro rearing of queen stingless bees can improve meliponiculture management and conservation efforts. Herein, we explored the efficacy of in vitro queen rearing for Heterotrigona itama, assessing the queen's body size, reproductive organ size (ovary and spermatheca), acceptance rate into new, small colonies, and mating frequency. H. itama larvae developed into queens when fed with 120 μL-150 μL of larval food, resulting in in vitro queens having body sizes similar to those of naturally produced queens. Microscopic analysis revealed well-developed ovaries and spermathecae in in vitro-reared queens, unlike the smaller ovaries and the absence of spermathecae in the naturally produced workers. Acceptance of in vitro-reared queens was independent of worker age, and mating frequency was low but not significantly different from naturally produced queens. These findings could enhance stingless beekeeping practices and conservation efforts for the native stingless bee species.

SolBeePopecotox: A Population Model for Pesticide Risk Assessments of Solitary Bees.

In agricultural landscapes, solitary bees occur in a large diversity of species and are important for crop and wildflower pollination. They are distinguished from honey bees and bumble bees by their solitary lifestyle as well as different nesting strategies, phenologies, and floral preferences. Their ecological traits and presence in agricultural landscapes imply potential exposure to pesticides and suggest a need to conduct ecological risk assessments for solitary bees. However, assessing risks to the large diversity of managed and wild bees across landscapes and regions poses a formidable challenge. Population models provide tools to estimate potential population-level effects of pesticide exposures, can support field study design and interpretation, and can be applied to expand study data to untested conditions. We present a population model for solitary bees, SolBeePopecotox, developed for use in the context of ecological risk assessments. The trait-based model extends a previous version with the explicit representation of exposures to pesticides from relevant routes. Effects are implemented in the model using a simplified toxicokinetic-toxicodynamic model, BeeGUTS (GUTS = generalized unified threshold model for survival), adapted specifically for bees. We evaluated the model with data from semifield studies conducted with the red mason bee, Osmia bicornis, in which bees were foraging in tunnels over control and insecticide-treated oilseed rape fields. We extended the simulations to capture hypothetical semifield studies with two soil-nesting species, Nomia melanderi and Eucera pruinosa, which are difficult to test in empirical studies. The model provides a versatile tool for higher-tier risk assessments, for instance, to estimate effects of potential exposures, expanding available study data to untested species, environmental conditions, or exposure scenarios. Environ Toxicol Chem 2024;00:1-17. © 2024 SETAC.

Plant versus pollinator protection: balancing pest management against floral contamination for insecticide use in Midwestern US cucurbits.

Controlling crop pests while conserving pollinators is challenging, particularly when prophylactically applying broad-spectrum, systemic insecticides such as neonicotinoids. Systemic insecticides are often used in conventional agriculture in commercial settings, but the conditions that optimally balance pest management and pollination are poorly understood. We investigated how insecticide application strategies control pests and expose pollinators to insecticides with an observational study of cucurbit crops in the Midwestern United States. To define the window of protection and potential pollinator exposure resulting from alternative insecticide application strategies, we surveyed 62 farms cultivating cucumber, watermelon, or pumpkin across 2 yr. We evaluated insecticide regimes, abundance of striped and spotted cucumber beetles (Acalymma vittatum [Fabricius] and Diabrotica undecimpunctata Mannerheim), and insecticide residues in leaves, pollen, and nectar. We found that growers used neonicotinoids (thiamethoxam and imidacloprid) at planting in all cucumber and pumpkin and approximately half of watermelon farms. In cucumber, foliar thiamethoxam levels were orders of magnitude higher than the other crops, excluding nearly all beetles from fields. In watermelon and pumpkin, neonicotinoids applied at planting resulted in 4-8wk of protection before beetle populations increased. Floral insecticide concentrations correlated strongly with foliar concentrations across all crops, resulting in high potential exposure to pollinators in cucumber and low-moderate exposure in pumpkin and watermelon. Thus, the highest-input insecticide regimes maintained cucumber beetles far below economic thresholds while also exposing pollinators to the highest pollen and nectar insecticide concentrations. In cucurbits, reducing pesticide inputs will likely better balance crop protection and pollination, reduce costs, and improve yields.

How pollinator dependence may mediate farmer adoption of pollinator supporting practices and perceptions: a case study from western France

There is limited knowledge on why farmers adopt pollinator-supporting practices, which is crucial to stimulate their adoption. The dependence of farmers on pollination may influence their perception of pollinators and their willingness to adopt these practices. We addressed why farmers adopt pollinator-supporting practices using a 2011 survey conducted within a cereal plain in western France, where farmers were moderately dependent on pollination for crops like oilseed rape and sunflower. We assessed the factors influencing the adoption of practices to promote pollination, including pollination dependence. We found no effect for pollination dependence. Conversely, we found that farm size, pesticide use, advisory services and the perception of costs decreased the willingness to adopt, while older farmers were more incline to adopt. We also evaluated perceptions related to pollinators: more than 85% of farmers considered bees important for crop production and recognized pesticides as a major cause of decline. We found no effect of pollination dependence on farmers’ perceptions. Compared to similar studies over the past decade, we found similarities, particularly regarding pollinator-related perceptions. Finally, we compared the willingness to adopt in 2011 with the actual adoption in 2024, showing that there has been little change. This raises questions on the pathways to promote the adoption of pollinator-supporting practices to ensure for the future of pollinator conservation.

Physiological effects of field concentrations and sublethal concentrations of sulfoxaflor on Apis mellifera.

Bees (Apis mellifera), as important pollinators of agricultural crops, are at risk when pesticides are used. Sulfoxaflor is a new insecticide which acts on the nicotinic acetylcholine receptor (nAChR) in a similar way to neonicotinoids. The goal of this study is to evaluate the toxicity of sulfoxaflor and its effect on the A. mellifera exposure. Initially, developmental indicators such as larval survival, pupation, and eclosion were inhibited by 5.0 mg/L (field concentration) sulfoxaflor. In the pupal stage, fat content was significantly increased, while the glycogen content decreased. In addition, A. mellifera heads were treated with 2.0 mg/L (sublethal concentration) of sulfoxaflor and analyzed by RNA sequencing. The transcriptome results indicated that 2.0 mg/L amounts of sulfoxaflor have adverse effects on the immune, digestive, and nervous systems. Sulfoxaflor down-regulated the expression of many genes involved in immunity, detoxification, the myosin cytoskeleton, sensory neurons, and odor-binding proteins. Field concentration and sublethal concentration were used for the combined analysis of honeybees. The effect of sublethal concentration of sulfoxaflor on honeybees was studied for the first time from the perspective of transcriptome sequencing of honeybee head. A preliminary study was carried out on the stress of sulfoxaflor at sublethal concentration on honeybee workers, which has certain research significance and can provide theoretical basis for the use of sulfoxaflor in the field environment. © 2024 Society of Chemical Industry.

Impact of tillage intensity and an invasive grass on plant-pollinator networks in riparian agroecosystems

Insects are a main component of a stable ecosystem and influence crop production. Pollinators, in particular, by regulating pollination between flowers, shape and secure plant communities around crop fields. They are also essential for food provisioning by sustaining the pollination of crops. Studies in recent decades have been covering the mixture of effects various factors have on pollinators. However, there is still a gap in understanding how different taxa in pollinator guilds respond to these pressures and how is network structure affected by it. Therefore, here we tried to further uncover the complex relationship between habitat suitability and pollinator biodiversity in an agro-riparian matrix. Using bipartite network analysis and geographical information systems (GIS) in four sites with different land cover configuration, we assessed faunal and floral diversity, land cover differences and network metrics. Hymenoptera were responsible for most of the visits, while also exhibiting higher levels of richness across sites. Lepidoptera on the other hand, were the order less represented. Overall, tillage intensity and Arundo donax were determinant in differences in the number of visits for both orders, with Diptera and Coleoptera being less affected. However, results regarding visitation rates reported tillage’s higher explanatory power, in comparison with A. donax. Intensive sites showed significantly higher levels of nestedness and lower specialization and diversity across taxa. The results suggest that intensive agriculture and exotic species infestation can impact pollinator taxa differently, thus influencing network structure. By scoping network metrics, we can better determine what species are more affected by agricultural expansion, assess ecosystem resilience and consequently, determine appropriate conservation measures to maintain stable plant-pollinator networks.

Fecal transplant allows transmission of the gut microbiota in honey bees.

Honey bees are crucial pollinators for many crops and wildflowers. They are also powerful models for studying microbiome-host interactions. However, current methods rely on gut tissue disruption to analyze microbiota composition and use gut homogenates to inoculate microbiota-deprived bees. Here, we provide two new and non-invasive approaches that will open doors to longitudinal studies: fecal sampling and transplantation. Furthermore, our findings provide insights into gut microbiota transmission in social insects by showing that ingestion of fecal matter can result in gut microbiota acquisition.

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.

Pollination efficiency of important insect visitors on pomegranate (Punica granatum) under mid hill conditions of Himachal Pradesh

Insect pollinators are found to be highly significant in enhancing the quality fruit production and productivity. The experiment was conducted during April–May 2020 and 2021 at Dr Y. S. Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh to determine the pollination indices of significant insect pollinators visiting pomegranate (Punica granatum L.). The data on pooled basis from two years revealed that Bombus haemorrhoidalis visited most number of flowers during the day (4.96 flowers/min) followed by Apis mellifera (4.24), Apis cerana (3.95), Apis dorsata (3.76) and Episyrphus balteatus (3.09). The time spent on each flower was maximum by A. cerana (17.10 sec/flower) followed by E. balteatus (17.04 sec), A. dorsata (14.20 sec), A. mellifera (13.07 sec) and haemorrhoidalis (5.36 sec) irrespective of different day hours. A. mellifera (5.43 bees/m2/2 min) activity was maximum followed by A. cerana (5.06), E. balteatus (2.91 visitors/m2/2 min), B. haemorrhoidalis (1.72) and A. dorsata (1.37). Data on loose pollen grains for the two years revealed that A. dorsata adhered maximum number of loose pollen grains (357.00 thousand) followed by B. haemorrhoidalis (283.00 thousand), A. mellifera (98.00 thousand), cerana (41.00 thousand) and solitary bees (28.00 thousand). A. mellifera scored highest pollination index and A. dorsata scored least pollination index. A. mellifera, A. cerana and B. haemorrhoidalis are the primary pollinators that increase pomegranate pollination efficiency whereas A. dorsata, E. baltaeatus and solitary bees are supplementary insects improving pollination in various crops including pomegranate. A. mellifera, A. cerana, B. haemorrhoidalis and A. dorsata were main foragers of pomegranate flowers ensuring effective and efficient pollination.

Shared use of a mass‐flowering crop drives dietary niche overlap between managed honeybees and bumblebees

Abstract Resource competition between wild pollinators and managed honeybees (Apis mellifera) has the potential to detrimentally impact insect biodiversity as well as wild plant and crop pollination. As honeybees are central place foragers, their competitive impact on wild bees is expected to be structured by hive proximity, in conjunction with foraging decisions related to landscape‐level resource availability. Yet, how these factors structure dietary niche overlap between wild bees and managed honeybees remains unclear. We conducted a field experiment in seminatural grasslands, where honeybee foraging densities and niche overlap with buff‐tailed bumblebees (Bombus terrestris) were measured at four distances (<100, 500, 1000 and 2000 m) from experimentally placed apiaries, during and after the blooming period of mass‐flowering oilseed rape (Brassica napus). We measured honeybee foraging densities using standardized transect surveys, and quantified species diet composition and dietary niche overlap from pollen samples collected from both bee species. Honeybee foraging densities were highest near apiaries and declined sharply beyond 500 m from the apiaries. However, niche overlap was unrelated to hive proximity but positively related to the availability of oilseed rape. Furthermore, there were significant inter‐ and intraspecific differences in pollen diet composition and breadth throughout the season. Synthesis and applications: Niche overlap between honeybees and bumblebees in agricultural environments was due to resource sharing of mass‐flowering oilseed rape. When both honeybees and bumblebees predominantly forage on wild plants, they maintain distinct pollen diets, suggesting there is a low risk of resource competition between these generalist taxa. Conservation actions that promote floral resource availability and diversity in agricultural landscapes are crucial to maintain niche differentiation between managed honeybees and wild bees.

Diversity of plant pollen sources, microbial communities, and phenolic compounds present in bee pollen and bee bread.

The pollination of several crops, as well as wild plants, depends on honeybees. To get the nutrients required for growth and survival, honeybee colonies are dependent on pollen supply. Bee pollen (BP) is partially packed in honeycomb cells and processed into beebread (BB) by microbial metabolism. The composition of pollen is highly variable and is mainly dependent on ecological habitat, geographical origin, honey plants, climatic conditions, and seasonal variations. Although there are important differences between the BP and the BB, little comparative chemical and microbiological data on this topic exists in the literature, particularly for samples with the same origin. In this study, BP and BB pollen samples were collected from two apiaries located in the Campania and Molise regions of Southern Italy. Phenolic profiles were detected via HPLC, while antioxidant activity was determined by ABTS·+ and DPPH· assay. The next-generation sequencing (NGS) based on RNA analysis of 16S (rRNA) and internal transcribed spacer (ITS2) regions were used to investigate the microbial community (bacteria and fungi) and botanical origin of the BP and BB. Chemical analysis showed a higher content of flavonols in BP (rutin, myricetin, quercetin, and kaempferol), while in BB there was a higher content of phenolic acids. The NGS analysis revealed that the microbial communities and pollen sources are dependent on the geographical location of apiaries. In addition, diversity was highlighted between the microbial communities present in the BP and BB samples collected from each apiary.

Agricultural specialisation increases the vulnerability of pollination services for smallholder farmers

Abstract Smallholder farms make up 84% of all farms worldwide and feed 2 billion people. These farms are heavily reliant on ecosystem services and vulnerable to environmental change, yet under‐represented in the ecological literature. The high diversity of crops in these systems makes it challenging to identify and manage the best providers of an ecosystem service, such as the best pollinators to meet the needs of multiple crops. It is also unclear whether ecosystem service requirements change as smallholders transition towards more specialised commercial farming—an increasing trend worldwide. Here, we present a new metric for predicting the species providing ecosystem services in diverse multi‐crop farming systems. Working in 10 smallholder villages in rural Nepal, we use this metric to test whether key pollinators, and the management actions that support them, differ based on a farmers' agricultural priority (producing nutritious food to feed the family vs. generating income from cash crops). We also test whether the resilience of pollination services changes as farmers specialise on cash crops. We show that a farmers' agricultural priority can determine the community of pollinators they rely upon. Wild insects including bumblebees, solitary bees and flies provided the majority of the pollination service underpinning nutrient production, while income generation was much more dependent on a single species—the domesticated honeybee Apis cerana. The significantly lower diversity of pollinators supporting income generation leaves cash crop farmers more vulnerable to pollinator declines. Regardless of a farmers' agricultural priority, the same collection of wild plant species (mostly herbaceous weeds and shrubs) were important for supporting crop pollinators with floral resources. Promoting these wild plants is likely to enhance pollination services for all farmers in the region. Synthesis and applications. We highlight the increased vulnerability of pollination services when smallholders transition to specialised cash crop farming and emphasise the role of crop, pollinator and wild plant diversity in mitigating this risk. The method we present could be readily applied to other smallholder settings across the world to help characterise and manage the ecosystem services underpinning the livelihoods and nutritional health of smallholder families.

Acute toxicity of the fungicide captan to honey bees and mixed evidence for synergism with the insecticide thiamethoxam

Honey bees are commonly co-exposed to pesticides during crop pollination, including the fungicide captan and neonicotinoid insecticide thiamethoxam. We assessed the impact of exposure to these two pesticides individually and in combination, at a range of field-realistic doses. In laboratory assays, mortality of larvae treated with captan was 80–90% greater than controls, dose-independent, and similar to mortality from the lowest dose of thiamethoxam. There was evidence of synergism (i.e., a non-additive response) from captan-thiamethoxam co-exposure at the highest dose of thiamethoxam, but not at lower doses. In the field, we exposed whole colonies to the lowest doses used in the laboratory. Exposure to captan and thiamethoxam individually and in combination resulted in minimal impacts on population growth or colony mortality, and there was no evidence of synergism or antagonism. These results suggest captan and thiamethoxam are each acutely toxic to immature honey bees, but whole colonies can potentially compensate for detrimental effects, at least at the low doses used in our field trial, or that methodological differences of the field experiment impacted results (e.g., dilution of treatments with natural pollen). If compensation occurred, further work is needed to assess how it occurred, potentially via increased queen egg laying, and whether short-term compensation leads to long-term costs. Further work is also needed for other crop pollinators that lack the social detoxification capabilities of honey bee colonies and may be less resilient to pesticides.

Crops dependency on pollinators to secure pollination success and fruit development: A case study of almond varieties from Morocco

AbstractThe contribution of insects to pollination constitutes a globally important ecosystem service. Due to the increasing demand for entomophilous crops, the nutritional and economic importance of insect‐pollinated crops and the inability of managed pollinators (Apis mellifera L) to meet the high demand for their services indicate that agriculture heavily relies on wild pollinators. Almonds are an economically valuable crop in Morocco. Therefore, it is essential to understand the fundamental pollination requirements of major almond varieties to promote their production. The main objectives of this study were to assess the dependency of three almond cultivars (Espoir, Largueta and Planeta) on insect pollination, and then to evaluate the pollination deficit resulting from the lack of these pollinators. For this purpose, we used insect‐proof net bags constructed around branches of almond trees to compare fruit set and yield with open and open + hand‐pollinated flowers. The results of the fruit set experiment confirmed that all three varieties require insect pollination, as fruit set and yield were significantly higher in insect‐pollinated than insect‐isolated trees. All three almond varieties were categorized as obligatory dependent on biotic pollinators. In addition, two out of the three studied almond varieties showed high pollination deficit resulting from the lower abundance and/or diversity of pollinating insects. The results of the current study highlights the important role of insect pollinators for almond crops and the urgent need for the implementation of sustainable strategies to preserve pollinators within agricultural ecosystems.

Osmia lignaria (Hymenoptera: Megachilidae) increase pollination of Washington sweet cherry and pear crops.

Apis mellifera Linnaeus (Hymenoptera: Apis), honey bees, are the most widely used managed crop pollinators. However, their high rental cost and uncertain availability for North American orchard crops have motivated growers to explore alternative pollination options. We examined whether adding solitary, spring-flying Osmia lignaria Say (Hymenoptera: Megachilidae), blue orchard bees, as co-pollinators with A. mellifera in Washington sweet cherry and pear orchards enhances fruit set and yield compared to the use of A. mellifera alone. We added managed O. lignaria to orchard sites where A. mellifera hives were already present. Fruit set, fruit yield, and O. lignaria reproduction at O. lignaria-supplemented sites were compared to nearby, paired sites pollinated only by A. mellifera (3 paired cherry and 3 paired pear sites). For both crops, the addition of O. lignaria significantly increased fruit set but did not yield at harvest. Microscopic inspection of pollen grains from O. lignaria nest cell provisions confirmed that O. lignaria primarily visited orchard flowers. Mean retention of O. lignaria in cherry orchards was slightly higher (65%) than O. lignaria retention reported in other orchard crops (30%-60%). However, retention in pear orchards was much lower (≤20%). These results show that supplementing hives with O. lignaria in Washington spring orchard crops can increase overall pollination, but that trees fail to bear developing fruit to maturity. The strategy of using co-pollinators, O. lignaria and A. mellifera, in US orchards may act as "pollination insurance" when A. mellifera hives are in low supply or when the weather is not amenable for A. mellifera flight during the bloom period.