Larval oral exposure to thiacloprid : dose-response toxicity testing in solitary bees, Osmia spp. (Hymenoptera: Megachilidae)

Risk assessment of pesticides involves ecotoxicological testing. In case pesticide exposure to bees is likely, toxicity tests are performed with honey bees (Apis mellifera), with a tiered approach, for which validated and internationally accepted test protocols exist. However, concerns have grown regarding the protection of non-Apis bees [bumble bees (Bombus spp.), solitary and stingless bees], given their different life cycles and therefore distinct exposure routes. Larvae of solitary bees of the genus Osmia feed on unprocessed pollen during development, yet no toxicity test protocol is internationally accepted or validated to assess the impact of pesticide exposure during this stage of their life cycle. Therefore, the purpose of this study is to further validate a test protocol with two solitary bee species (O. cornuta and O. bicornis) to assess lethal and sublethal effects of pesticide exposure on larval development. Larvae were exposed to thiacloprid (neonicotinoid insecticide) mixed in a new, artificial pollen provision. Both lethal (developmental and winter mortality) and sublethal endpoints (larval development time, pollen provision consumption, cocoon weight, emergence time and adult longevity) were recorded. Effects of lower, more environmentally realistic doses were only reflected in sublethal endpoints. In both bee species, thiacloprid treatment was associated with increased developmental mortality and larval development time, and decreased pollen provision consumption and cocoon weight. The test protocol proved valid and robust and showed that for higher doses of thiacloprid the acute endpoint (larval mortality) is sufficient. In addition, new insights needed to develop a standardized test protocol were acquired, such as testing of a positive control for the first time and selection of male and female individuals at egg level

Reduced nest development of reared Bombus terrestris within apiary dense human-modified landscapes

Wild bees are in decline on a local to global scale. The presence of managed honey bees can lead to competition for resources with wild bee species, which has not been investigated so far for human-modified landscapes. In this study we assess if managed honey bee hive density influence nest development (biomass) of bumble bees, an important trait affecting fitness. We hypothesize that domesticated honey bees can negatively affect Bombus terrestris nest development in human-modified landscapes. In Flanders, Belgium, where such landscapes are dominantly present, we selected 11 locations with landscape metrics ranging from urban to agricultural. The bee hive locations were mapped and each location contained one apiary dense (AD) and one apiary sparse (AS) study site (mean density of 7.6 +/- 5.7 managed honey bee hives per km(2) in AD sites). We assessed the effect of apiary density on the reproduction of reared B. terrestris nests. Reared B. terrestris nests had more biomass increase over 8 weeks in apiary sparse (AS) sites compared to nests located in apiary dense (AD) sites. This effect was mainly visible in urban locations, where nest in AS sites have 99.25 +/- 60.99 g more biomass increase compared to nest in urban AD sites. Additionally, we found that managed bumble bee nests had higher biomass increase in urban locations. We conclude that the density of bee hives is a factor to consider in regard to interspecific competition between domesticated honey bees and bumble bees

CropPol: a dynamic, open and global database on crop pollination

Seventy five percent of the world's food crops benefit from insect pollination. Hence, there has been increased interest in how global change drivers impact this critical ecosystem service. Because standardized data on crop pollination are rarely available, we are limited in our capacity to understand the variation in pollination benefits to crop yield, as well as to anticipate changes in this service, develop predictions, and inform management actions. Here, we present CropPol, a dynamic, open and global database on crop pollination. It contains measurements recorded from 202 crop studies, covering 3,394 field observations, 2,552 yield measurements (i.e. berry weight, number of fruits and kg per hectare, among others), and 47,752 insect records from 48 commercial crops distributed around the globe. CropPol comprises 32 of the 87 leading global crops and commodities that are pollinator dependent. Malus domestica is the most represented crop (32 studies), followed by Brassica napus (22 studies), Vaccinium corymbosum (13 studies), and Citrullus lanatus (12 studies). The most abundant pollinator guilds recorded are honey bees (34.22% counts), bumblebees (19.19%), flies other than Syrphidae and Bombyliidae (13.18%), other wild bees (13.13%), beetles (10.97%), Syrphidae (4.87%), and Bombyliidae (0.05%). Locations comprise 34 countries distributed among Europe (76 studies), Northern America (60), Latin America and the Caribbean (29), Asia (20), Oceania (10), and Africa (7). Sampling spans three decades and is concentrated on 2001-05 (21 studies), 2006-10 (40), 2011-15 (88), and 2016-20 (50). This is the most comprehensive open global data set on measurements of crop flower visitors, crop pollinators and pollination to date, and we encourage researchers to add more datasets to this database in the future. This data set is released for non-commercial use only. Credits should be given to this paper (i.e., proper citation), and the products generated with this database should be shared under the same license terms (CC BY-NC-SA). This article is protected by copyright. All rights reserved

Interaction effects of different drivers of wild bee decline and their influence on host–pathogen dynamics

Wild bee decline is a multi-factorial problem, yet it is crucial to understand the impact of a single driver. Hereto the interaction effects of wild bee decline with multiple natural and anthropogenic stressors need to be clear. This is also true for the driver 'pathogens', as stressor induced disturbances of natural host-pathogen dynamics can unbalance settled virulence equilibria. Invasive species, bee domestication, habitat loss, climate changes and insecticides are recognized drivers of wild bee decline, but all influence host-pathogen dynamics as well. Many wild bee pathogens have multiple hosts, which relaxes the host-density limitation of virulence evolution. In conclusion, disturbances of bee-pathogen dynamics can be compared to a game of Russian roulette

Wildflowers availability not a land-use type affects commercial bumblebee foraging on the strawberry

Managed bumble bees can be used to increase crop yield quality and quantity in areas where wild pollinators are insufficient. The success of introduced pollinators is highly dependent on the surrounding environment, competition with other pollinators, food source relevance, and foraging behavior.This study was supported by the Estonian Ministry of Education and Research project IUT36-2.This study was supported by the Estonian Ministry of Education and Research project IUT36-2

Recommendations for standardized oral toxicity test protocols for larvae of solitary bees, Osmia spp.

Effects of pesticides have been debated as one of the causes of worldwide declines of bee populations. Improving the risk assessment of pesticides on bees is important to halt these declines. Pesticide risk assessment today mainly focuses on one bee species, the honey bee. Because of differences in life cycles among bee species, this risk assessment needs to be adapted to take these differences into account. For both the adult and larval life stages, development of test protocols for solitary bees is required. Here, we summarize the current knowledge on larval tier 1 tests based on the first test protocols for solitary bee larvae available in the literature. As the ecology and rearing of solitary bees of the genus Osmia spp. are well known, we propose this genus as a model species in a first step to develop protocols for solitary species. In addition, we discuss guidelines, relevant endpoints, and research needs for the development of a standardized oral toxicity test protocol of solitary bee larvae

Linking remote sensing data to the estimation of pollination services in agroecosystems

Wild bees are key providers of pollination services in agroecosystems. The abundance of these pollinators and the ecosystem services they provide rely on supporting resources in the landscape. Spatially explicit models that quantify wild bee abundance and pollination services in food crops are built on the foundations of foraging and nesting resources. This dependence limits model implementation as land-cover maps and pollination experts capable of evaluating habitat resource quality are scarce. This study presents a novel approach to assessing crop pollination services using remote sensing data (RSD) as an alternative to the more conventional use of land-cover data and local expertise on spatially explicit models. We used landscape characteristics derived from remote sensors to qualify nesting resources in the landscape and to evaluate the delivery of pollination services by mining bees (Andrena spp.) in 30 fruit orchards located in the Flemish region of Belgium. For this study, we selected mining bees for their importance as local pollinators and underground nesting behavior. We compared the estimated pollination services derived from RSD with those derived from the conventional qualification of nesting resources. We did not observe significant differences (p = 0.68) in the variation in mining bee activity predicted by the two spatial models. Estimated pollination services derived from RSD and conventional characterizations explained 69% and 72% of the total variation, respectively. These results confirmed that RSD can deliver nesting suitability characterizations sufficient for estimating pollination services. This research also illustrates the importance of nesting resources and landscape characteristics when estimating pollination services delivered by insects like mining bees. Our results support the development of holistic agroenvironmental policies that rely on modern tools like remote sensors and promote pollinators by considering nesting resources

Increased compositional heterogeneity of mass-flowering orchard crops does not promote wild bee abundance in orchards

Due to increasing difficulties to maintain semi-natural habitat within agricultural landscapes, management of the agricultural matrix may provide a more realistic approach to support farmland biodiversity and associated ecosystem services. We hypothesize that orchard compositional heterogeneity (OCH), that is, different mass-flowering crops with sequential blooming periods, may support pollinators through continuous abundance of floral resources. We assessed whether increased OCH at the landscape level had a positive effect on wild bee abundances in sweet cherry and apple orchards during bloom. We monitored 15 sweet cherry and 14 apple orchards in Flanders, Belgium, situated along a gradient of OCH. We performed pollinator surveys during bloom to measure wild bee and honey bee abundance and monitored fruit development to assess fruit set and quality. We found no positive effect of OCH on wild pollinator abundance in our study system. Solitary bees showed contrasting responses between crops. Bumble bees showed no response. Wild pollinator abundance had a positive effect on sweet cherry fruit set and apple seed set. Our results imply that increasing crop compositional heterogeneity solely in terms of orchard crops with a limited difference in bloom phenology may prove to be insufficient to support pollinators. We confirm the importance of wild pollinators for pollination services in horticulture