Oilseed Rape Flowers Research Articles

Unraveling the mechanism of flower color variation in Brassica napus by integrated metabolome and transcriptome analyses.

Brassica napus is one of the most important oil crops in the world. Breeding oilseed rape with colorful flowers can greatly enhance the ornamental value of B. napus and thus improve the economic benefits of planting. As water-soluble flavonoid secondary metabolites, anthocyanins are very important for the synthesis and accumulation of pigments in the petals of plants, giving them a wide range of bright colors. Despite the documentation of over 60 distinct flower shades in B. napus, the intricacies underlying flower color variation remain elusive. Particularly, the mechanisms driving color development across varying flower color backgrounds necessitate further comprehensive investigation. This research undertook a comprehensive exploration through the integration of transcriptome and metabolome analyses to pinpoint pivotal genes and metabolites underpinning an array of flower colors, including beige, beige-red, yellow, orange-red, deep orange-red, white, light-purple, and purple. First, we used a two-way BLAST search to find 275 genes in the reference genome of B. napus Darmor v10 that were involved in making anthocyanins. The subsequent scrutiny of RNA-seq outcomes underscored notable upregulation in the structural genes F3H and UGT, alongside the MYB75, GL3, and TTG1 transcriptional regulators within petals, showing anthocyanin accumulation. By synergizing this data with a weighted gene co-expression network analysis, we identified CHS, F3H, MYB75, MYB12, and MYB111 as the key players driving anthocyanin synthesis in beige-red, orange-red, deep orange-red, light-purple, and purple petals. By integrating transcriptome and weighted gene co-expression network analysis findings with anthocyanin metabolism data, it is hypothesized that the upregulation of MYB75, which, in turn, enhances F3H expression, plays a pivotal role in the development of pigmented oilseed rape flowers. These findings help to understand the transcriptional regulation of anthocyanin biosynthesis in B. napus and provide valuable genetic resources for breeding B. napus varieties with novel flower colors.

Use of an unmanned aerial vehicle for monitoring and prediction of oilseed rape crop performance.

The flowering stage of oilseed rape (Brassica napus L.) is of vital interest in precision agriculture. It has been shown that data describing the flower production of oilseed rape (OSR), at stage 3, in spring can be used to predict seed yield at harvest. Traditional field-based techniques for assessing OSR flowers are based on a visual assessment which is subjective and time consuming. However, a high throughput phenotyping technique, using an unmanned aerial vehicle (UAV) with multispectral image (MSI) camera, was used to investigate the growth stages of OSR (in terms of crop height) and to quantify its flower production. A simplified approach using a normalised difference yellowness index (NDYI) was coupled with an iso-cluster classification method to quantify the number of OSR flower pixels and incorporate the data into an OSR seed yield estimation. The estimated OSR seed yield showed strong correlation with the actual OSR seed yield (R2 = 0.86), as determined using in-situ sensors mounted on the combine harvester. Also, using our approach allowed the variation in crop height to be assessed across all growing stages; the maximum crop height of 1.35 m OSR was observed at the flowering stage. This methodology is proposed for effectively predicting seed yield 3 months prior to harvesting.

Significance of Direct and Indirect Impacts of Temperature Increase Driven by Climate Change on Threat to Oilseed Rape Posed by Sclerotinia sclerotiorum.

Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, threatens oilseed rape (Brassica napus) crops internationally. The development of this disease is strongly controlled by the weather, which is why global climate change is likely to influence its spread and impact. Climate change may affect the pathogen directly or indirectly via the host plant. This study investigates the potential impact of climate warming on Sclerotinia stem rot severity in oilseed rape in Poland. The aim of this investigation was to assess the relationship between the direct impact (DI) and indirect impact (II) of climate change on disease severity using the 4.5 and 8.5 representative concentration pathways (RCPs). Under the RCP4.5 scenario, nearly 60% of the simulations performed for 16 regions in four periods (2020-2039, 2040-2059, 2060-2079, 2080-2099) showed reductions in disease severity in comparison to those conducted for 1986-2005, while under RCP 8.5, this reduction was generated for nearly 90% of the cases. The effect of the RCP scenario on clustering the regions according to the value of Sclerotinia stem rot severity was also investigated. The simulations revealed that, for all periods, the lowest disease severities are expected for Zachodniopomorskie and Pomorskie. The results obtained also show the superior effects of the II over the DI on Sclerotinia stem rot severity in the future. Under the RCP4.5 scenario, the rate of IIs was greater than that of DIs for 10 regions, while under RCP8.5, this relationship was registered for 16 regions. These outcomes result from the acceleration of the oilseed rape flowering period triggered by expected temperature increases. The novelty of this study lies in a detailed analysis of the relationships between the DI and II of climate change, expressed numerically, for 16 regions in Poland. The obtained results highlight the role of the indirect impact in shaping disease severity and indicate that it should be incorporated into assessment methods of climate change effects alongside the direct impact.

Effect of Honey Bee <i>Apis mellifera</i> L. Pollination on Oilseed Rape

An experiment was conducted to survey insect visitors and the effect of different modes of pollination on quantity of oilseed rape. Survey revealed that a wide range of insect species, including honey bees, and hover flies, house fly and ensign fly were frequent on oilseed rape flowers where honey bees (Apis dorsata and Apis mellifera) were dominant. Effect of pollination revealed that in bee pollinated (BP) plants the number of pods/ plant, number of seeds/ pod, weight of 1000 seeds (g) and yield/ ha were 16.38, 20.18, 6.75 and 14.27% higher than open/naturally pollinated (NP) plants, respectively. Without (WP) pollinators the number of pods/ plant, number of seeds/ pod, weight of 1000 seeds (g) and yield/ ha were the 19.38, 37.05, 8.10 and 32.63% lower than naturally pollinated (NP) plants, respectively. Bee pollination is the most effective and cheaper device for seed production in rapeseed and mustard.

Yield Loss and Integrated Disease Control of Rhizoctonia solani AG2-1 Using Seed Treatment and Sowing Rate of Oilseed Rape.

Rhizoctonia solani anastomosis group (AG) 2-1 is an ubiquitous soilborne pathogen causing severe damping-off of oilseed rape (OSR). In the absence of varietal resistance to AG2-1, there are limited methods for integrated disease management. The objectives of these field studies were to quantify yield losses due to AG2-1 and to determine the effectiveness of integrated control using sedaxane, fludioxonil, and metalaxyl-M applied as seed treatment on two OSR genotypes at a sowing rate of 40 (low) or 80 (high) seeds m-2. Crop assessments of green area index (GAI), vigor, and cabbage stem flea beetle (CSFB) Psylliodes chrysocephala damage were carried out at GS16, while pathogen DNA in soil was quantified using real-time PCR at GS32. Yield and seed weight losses of 41 and 18%, respectively, were associated with reduced establishment, GAI, vigor, and delayed development and flowering of OSR. Seed treatment reduced AG2-1 DNA in soil by 80%, resulting in a 94, 16, and 64% increase of establishment, thousand seed weight (TSW), and yield, respectively. Seed treatment also mitigated the effects of AG2-1 on delaying plant development, resulting in increased uniformity of crop flowering. OSR plants infected with AG2-1 suffered 27% more damage by the CSFB, indicating positive pathogen-pest interaction at the expense of the OSR host. Optimum control of AG2-1 infection was achieved by integrating low sowing rate and seed treatment. However, under dual pest and pathogen attack, high sowing rates should be combined with the use of seed treatment to mitigate seedling death and delayed development caused by AG2-1 and CSFB damage.

High ambient temperature impacts on flowering time in Brassica napus through both H2A.Z-dependent and independent mechanisms.

Knowledge concerning the integration of genetic pathways mediating the responses to environmental cues controlling flowering initiation in crops is scarce. Here, we reveal the diversity in oilseed rape (OSR) flowering response to high ambient temperature. Using a set of different spring OSR varieties, we found a consistent flowering delay at elevated temperatures. Remarkably, one of the varieties assayed exhibited the opposite behaviour. Several FT-like paralogs are plausible candidates to be part of the florigen in OSR. We revealed that BnaFTA2 plays a major role in temperature-dependent flowering initiation. Analysis of the H2A.Z histone variant occupancy at this locus in different Brassica napus varieties produced contrasting results, suggesting the involvement of additional molecular mechanisms in BnaFTA2 repression at high ambient temperature. Moreover, BnARP6 RNAi plants showed little accumulation of H2A.Z at high temperature while maintaining temperature sensitivity and delayed flowering. Furthermore, we found that H3K4me3 present in BnaFTA2 under inductive flowering conditions is reduced at high temperature, suggesting a role for this hallmark of transcriptionally active chromatin in the OSR flowering response to warming. Our work emphasises the plasticity of flowering responses in B. napus and offers venues to optimise this process in crop species grown under suboptimal environmental conditions.

The value of insect pollination to yield of oilseed rape (Brassica rapa) in Bangladesh

• Oilseed rape ( Brassica rapa) flowers were visited by different insect pollinators. • Insect pollination increased yield (>30%) and oil content(>1%) in B. rapa. • The value of insect pollination in B. rapa was $ US 26.92 million per year. • Management of good pollination services can ensure better yield in oilseed rape. Brassica rapa L., is a crop grown globally and studies have indicated that insect pollination can improve yields. However, the importance of insect pollination in this crop depends on cultivar reproductive biology, insect pollinator species and their abundances. In Bangladesh, the acreage of B. rapa for oilseed production has been expanding, but little is known about whether insects contribute to yield improvements. Using the commonly grown variety Tori-7, we found that plants with inflorescences left exposed to flower visiting insects (body width > 1.5 mm) had a 30.8% greater seed yield compared to those where insect flower visitors were excluded. Of 794 insect flower visiting individuals recorded from observation and trapping surveys conducted across four separate fields, Apis bees (four spp.) were the most abundant (66.1%), followed by flies Musca domestica (14.7%), Sepsis fulgens (6.3%) and hoverflies (3.0%; 3 spp; Syrphidae). Other flower visitors included ants, wasps, beetles, butterflies and moths. For the cultivar assessed, we calculated the economic value of oilseed rape was $US 87.5 million per annum in Bangladesh, of which the economic value of insect pollination was $US 26.92 million per annum. Thus, one in every four dollars earned by our Bangladeshi growers resulted from insect crop pollination. This demonstrates to growers the need to promote and protect insect pollination to optimize their economic returns.

Artificial field defects: A low-cost measure to support arthropod diversity in arable fields

Biodiversity is rapidly declining worldwide, with agricultural intensification being among the main drivers of this process. Effective conservation measures in agricultural landscapes are therefore urgently needed. Here we introduce a novel low-cost conservation measure called artificial field defects, i.e., areas where crop is not sown and spontaneous vegetation grows. To evaluate their biodiversity potential, we compared abundance and species richness of various arthropod taxa between artificially created field defects and control plots within oilseed rape (OSR) fields. The effectiveness of field defects to support biodiversity was examined using an experiment with a factorial design comparing OSR flowering and ripening phases, location of field defects (field edge vs interior) and field defect type (sown with a nectar-rich plant vs no sowing). Arthropod sampling was conducted by employing several complementary methods: pitfall trapping, pan trapping, sweep netting and individual counting. Butterflies, true bugs, bees and wasps were more abundant and species-rich in both types of defects than in OSR controls. In contrast, ground-dwelling taxa had more individuals and species in controls. Overall, arthropod abundance and species richness increased, and field defects became relatively more attractive, during OSR ripening compared to OSR flowering. Location of defects had little effect, with only butterfly and spider assemblages being more abundant and species-rich at field edges compared to interiors. Our data indicate that artificial field defects can provide a simple agri-environmental measure to support various arthropod groups. However, further studies are needed to assess their biodiversity value at the landscape scale, and evaluate the balance between costs and benefits for farmers.

Meteorological Variables That Affect the Beginning of Flowering of the Winter Oilseed Rape in the Czech Republic

Winter oilseed rape (Brassica napus) is one of the most cultivated oilseeds in the Czech Republic and belongs among major pollen allergens. Pollen allergies have an extensive clinical impact worldwide, and as well as in the Czech Republic. In this paper, meteorological variables such as mean air temperature, maximum and minimum air temperature, precipitation total and number of rainy days in the period 1991–2012 were studied using the PhenoClim phenological model to find the best predictor of the beginning of flowering of the Brassica napus in the Czech Republic. In addition, temporal and spatial evaluations of the beginning of flowering of the Brassica napus were examined at individual stations in different climatic zones within the same period. In total, three phenological stations at altitudes from 270 m asl to 533 m asl located in warm (W2), medium warm (MW7) or cold (C7) climatic zones were used for detailed evaluation. Based on the observation results at selected stations, the beginning of flowering of the Brassica napus advanced progressively in timing (nearly −15 days) in the 1991–2012 period. The base temperature and temperature sums were calculated for the beginning of flowering of the winter oilseed rape using the PhenoClim computer tool. As the most accurate predictor for the beginning of flowering of the Brassica napus, the mean air temperature was determined. The optimal start day for calculation was 30th January, the threshold (base temperature) was 6.0 °C and the temperature sum was 157.0 °C. The RMSE value was 4.77 and the MBE value was −3.00. The simulated data had a good correlation with the real observed data (the correlation coefficients were within the range from 0.56 to 0.76), and the PhenoClim model results indicate using them in the forecast modeling of the beginning of flowering of the Brassica napus in the Czech Republic.

Effects of Nitrogen Application Rate on Rhizosphere Microbial Diversity in Oilseed Rape (Brassica napus L.)

Nitrogen is one of the essential nutrients for rape growth and development, of which the demand is large. In order to reveal the response of rhizosphere microbial diversity on oilseed rape to the nitrogen fertilizer, four nitrogen application rates of N (170 kgN/hm2), N50% (85 kgN/hm2), N70% (119 kgN/hm2) and N150% (255 kgN/hm2) were set. The diversity and community structure of soil bacteria and fungi in seedling, flowering and mature stages of oilseed rape were analyzed based on the high-throughput sequencing technology. The results of rhizosphere soil microbial analysis showed that the dominant bacteria phyla were Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes and Cyanobacteria. The dominant fungi phyla were Ascomycota, Olpidiomycota and Basidiomycota. NMDS analysis showed that the community structure of soil bacteria and fungi changed significantly under nitrogen treatment. Cluster analysis showed that the bacteria at seedling and flowering stage had little effect under the condition of less nitrogen application, while the fungi had little effect on the rhizosphere soil microbial flora at flowering stage. At seedling stage, the diversity and richness of bacterial community in the rhizosphere of oilseed rape were lower under low nitrogen application (85 kgN/hm2). Bacteria and fungi in the rhizosphere soil of flowering oilseed rape maintained a higher community diversity under the condition of high nitrogen (255 kgN/hm2). The diversity of rhizosphere bacterial community was higher under conventional N application than under other N application.

Chemical defence in Brassicaceae against pollen beetles revealed by metabolomics and flower bud manipulation approaches.

Divergence of chemical plant defence mechanisms within the Brassicaceae can be utilized to identify means against specialized pest insects. Using a bioassay-driven approach, we (a) screened 24 different Brassica napus cultivars, B. napus resyntheses and related brassicaceous species for natural plant resistance against feeding adults of the pollen beetle (Brassicogethes aeneus), (b) tested for gender-specific feeding resistance, (c) analysed the flower bud metabolomes by a non-targeted approach and (d) tested single candidate compounds for their antifeedant activity. (a) In no-choice assays, beetles were allowed to feed on intact plants. Reduced feeding activity was mainly observed on Sinapis alba and Barbarea vulgaris but not on B. napus cultivars. (b) Males fed less and discriminated more in feeding than females. (c) Correlation of the metabolite abundances with the beetles' feeding activity revealed several glucosinolates, phenylpropanoids, flavonoids and saponins as potential antifeedants. (d) These were tested in dual-bud-choice assays developed for medium-throughput compound screening. Application of standard compounds on single oilseed rape flower buds revealed highly deterrent effects of glucobarbarin, oleanolic acid and hederagenin. These results help to understand chemical plant defence in the Brassicaceae and are of key importance for further breeding strategies for insect-resistant oilseed rape cultivars.

Crop pollination services: Complementary resource use by social vs solitary bees facing crops with contrasting flower supply

AbstractMany farmers are facing high economic risks if pollinator declines continue or temporal and spatial variation in wild bee communities cause reduced pollination services. Co‐flowering crops might compete for pollinators, while they also might facilitate the delivery of pollination services. This rarely studied topic is of particular interest with respect to the foraging decisions of bees from different functional groups and when more sparsely and mass‐flowering crops are in bloom at the same time.The abundance of honey bees, bumble bees and solitary bees in strawberry fields was quantified with transect walks along a gradient of oilseed rape (OSR) availability (product of OSR land cover and temporally changing OSR flower cover). We established a pollination experiment with pollination treatments (open‐, wind‐ and self‐pollination) to study the effects of insect pollination on strawberry fruit weight and quality.Changes in OSR availability exhibited contrasting effects on social versus solitary bees in strawberry fields. Bumble bees and honey bees were less abundant in strawberry fields when OSR availability was high, whereas solitary bees were facilitated. With more strawberry flowers, we found more bees in general.When flowers were open‐pollinated, they resulted in heavier fruits with better commercial grades compared to wind‐ and self‐pollinated flowers. A higher bee abundance enhanced the strawberry fruit weight and quality but depended on flower order and variety.Synthesis and applications. Sparsely flowering crops may compete with mass‐flowering crops for social bee pollinators, while solitary pollinators in the field might be evenly facilitated. To ensure best fruit weight and quality, it can be beneficial to support bee abundance in the field. While some social and solitary bee species can be managed for pollination services, wild bees, in particular solitary species, should be conserved and promoted for stable crop pollination services in dynamic agricultural landscapes.

Detecting flowering phenology in oil seed rape parcels with Sentinel-1 and -2 time series

A novel methodology is proposed to robustly map oil seed rape (OSR) flowering phenology from time series generated from the Copernicus Sentinel-1 (S1) and Sentinel-2 (S2) sensors. The time series are averaged at parcel level, initially for a set of 229 reference parcels for which multiple phenological observations on OSR flowering have been collected from April 21 to May 19, 2018. The set of OSR parcels is extended to a regional sample of 32,355 OSR parcels derived from a regional S2 classification. The study area comprises the northern Brandenburg and Mecklenburg-Vorpommern (N) and the southern Bavaria (S) regions in Germany. A method was developed to automatically compute peak flowering at parcel level from the S2 time signature of the Normalized Difference Yellow Index (NDYI) and from the local minimum in S1 VV polarized backscattering coefficients. Peak flowering was determined at a temporal accuracy of 1 to 4 days. A systematic flowering delay of 1 day was observed in the S1 detection compared to S2. Peak flowering differed by 12 days between the N and S. Considerable local variation was observed in the N-S parcel-level flowering gradient. Additional in-situ phenology observations at 70 Deutscher Wetterdienst (DWD) stations confirm the spatial and temporal consistency between S1 and S2 signatures and flowering phenology across both regions. Conditions during flowering strongly determine OSR yield, therefore, the capacity to continuously characterize spatially the timing of key flowering dates across large areas is key. To illustrate this, expected flowering dates were simulated assuming a single OSR variety with a 425 growing degree days (GDD) requirement to reach flowering. This GDD requirement was calculated based on parcel-level peak flowering dates and temperatures accumulated from 25-km gridded meteorological data. The correlation between simulated and S2 observed peak flowering dates still equaled 0.84 and 0.54 for the N and S respectively. These Sentinel-based parcel-level flowering parameters can be combined with weather data to support in-season predictions of OSR yield, area, and production. Our approach identified the unique temporal signatures of S1 and S2 associated with OSR flowering and can now be applied to monitor OSR phenology for parcels across the globe.

Effects of dropleg application technique during flowering of oilseed rape on insect pests

Spraying of insecticides and fungicides during the flowering stage of oilseed rape (Brassica napus L.) could be necessary to control insect pests (such as Ceutorhynchus obstrictus (Marsham) and Dasineura brassicae (Winnertz)) and pathogens (Sclerotinia sclerotiorum (Lib.) de Bary). In contrast to the conventional application technique, dropleg nozzles are kept below the flowering canopy to restrict the exposure of pollinators to active ingredients of insecticides. The Julius Kühn-Institut (JKI) tested the efficacy of different insecticides using the dropleg technique compared to the conventional technique, on insect pests in field trials conducted from 2015 to 2017 in the area of Braunschweig. The crop was treated at full flowering (BBCH 65) for three consecutive years. The tested insecticides were Biscaya (72 g a. i. ha−1 thiacloprid), Mavrik (48 g a. i. ha−1 tau-fluvalinate), and Mospilan SG (40 g a. i. ha−1 acetamiprid). The adults and larvae of oilseed rape pests that drop to the ground were collected using water trays. The emergence of new generation beetles (Brassicogethes aeneus (Fabricius), C. obstrictus) was recorded from BBCH 78 onwards, using photoeclectors. At least twice during each season, oilseed rape plants were assessed for D. brassicae injury. The new dropleg application technique showed similar efficacy on pest insects compared to the conventional spraying technique. Nevertheless, the abundance of pests was not always sufficient to get clear results. Results especially on D. brassicae indicate that the dropleg technique had a comparable efficacy under moderate pest pressure conditions observed in our study. Further research under conditions with a higher abundance of C. obstrictus, as well as research on the effects of dropleg technique on parasitoids of oilseed rape pests, is needed. The population of B. aeneus population was reduced slightly less using dropleg instead of conventional application technique. In all the years, the yields did not differ significantly with regard to the conventional and dropleg application techniques.

Flower age expressed in thermal time: is nectar secretion synchronous with pistil receptivity in oilseed rape (Brassica napus L.)?

Floral longevity can vary substantially with temperature in a given plant species. Thermal time has been widely used to measure developmental age of plants and poikilothermic organisms. We tested whether thermal time was suitable to express flower age to characterise the duration of pistil receptivity and that of nectar secretion in undisturbed flowers of oilseed rape (OSR), and whether these two functional processes were synchronous. Flower age was measured in a male fertile hybrid F1 line and in its male sterile (MS) parental line to determine if the presence of pollen affected the nectar secretion period. Hand pollinations and nectar samplings were conducted throughout the lifespan of OSR flowers on several flower cohorts from plants grown under tunnels under various temperature conditions. The number of seeds produced per flower was used as a proxy to assess the level of pistil receptivity at the time of hand-pollination. Thermal time was more suitable than calendar time to express OSR flower age. A phase of maturity followed by a phase of senescence took place in the two processes, and both proceeded faster as temperature increased. Nectar was secreted during the phase of full pistil receptivity, and, in the MS line, was then reabsorbed during the gradual decline of pistil receptivity. However, the nectar secretion period was extended beyond the onset of pistil senescence in the F1 line. OSR flowers invest in nectar secretion to attract insect pollinators at least to cover the whole receptivity period of their female part. Nectar secretion may be prolonged in pollen-laden male fertile flowers to attract insect pollinators longer to ensure as long as possible the probability of their pollen being disseminated. Flower senescence is triggered by pistil senescence, while the presence of pollen in anthers acts as an inhibitor and therefore delays flower senescence. Thermal time should henceforth be used to express more universally the age of plant organs and to model the duration of processes in relation to temperature, especially in the advent of global warming.

Impact of flower rewards on phytophagous insects: importance of pollen and nectar for the development of the pollen beetle (Brassicogethes aeneus)

Entomophilous plants reward pollinators with provision of nutrient-rich foods such as pollen and nectar. These rewards contain compounds that are essential to insect development and can be used by pollinators as well as herbivorous insects. The pollen beetle (Brassicogethes aeneus, syn. Meligethes aeneus) whose larvae develop in oilseed rape flowers (Brassica napus) is known to feed on pollen. Previous studies already showed the importance of pollen on the development of this insect but it seems that other resource, such as nectar, could also be used. The purpose of this study was to assess the respective roles of pollen and nectar on pollen beetle development. We tested their role with behavioural and developmental experiments using flowers where the presence and absence of nectar and pollen varied. Larvae, irrespective of their instar, fed both on anthers and nectar. Nectar did not influence larval development or adult survival while pollen influenced development by increasing both larval and adult weight. However, pollen did not affect larval or adult survival nor development time. These results indicate that pollen beetle larvae are adapted to deal with various diets and can complete their development without pollen or nectar.

Current and previous spatial distributions of oilseed rape fields influence the abundance and the body size of a solitary wild bee, Andrena cineraria, in permanent grasslands.

Wild bees are essential pollinators whose survival partly depends on the capacity of their environment to offer a sufficient amount of nectar and pollen. Semi-natural habitats and mass-flowering crops such as oilseed rape provide abundant floristic resources for bees. The aim of this study was to evaluate the influences of the spatial distribution of semi-natural habitats and oilseed rape fields on the abundance and the mean body size of a solitary bee in grasslands. We focused on a generalist mining bee, Andrena cineraria, that forages and reproduces during oilseed rape flowering. In 21 permanent grasslands of Eastern France, we captured 1 287 individuals (1 205 males and 82 females) and measured the body size of male individuals. The flower density in grasslands was quantified during bee captures (2016) and the landscape surrounding grasslands was characterized during two consecutive years (2015 and 2016). The influence of oilseed rape was tested through its distribution in the landscape during both the current year of bee sampling and the previous year. Bee abundance was positively influenced by the flower density in grasslands and by the area covered by oilseed rape around grasslands in the previous year. The mean body size of A. cineraria was explained by the interaction between flower density in the grassland and the distance to the nearest oilseed rape field in the current year: the flower density positively influenced the mean body size only in grasslands distant from oilseed rape. A. cineraria abundance and body size distribution were not affected by the area of semi-natural habitats in the landscape. The spatial distribution of oilseed rape fields (during both the current and the previous year) as well as the local density of grassland flowers drive both bee abundance and the mean value of an intraspecific trait (body size) in permanent grasslands. Space-time variations of bee abundance and mean body size in grasslands may have important ecological implications on plant pollination and on interspecific interactions between pollinators. Specifically, a competition between bee species for nesting sites might occur in oilseed rape rich landscapes, thus raising important conservation issues for bee species that do not benefit from oilseed rape resources.

Neonicotinoid residues in UK honey despite European Union moratorium.

Due to concerns over negative impacts on insect pollinators, the European Union has implemented a moratorium on the use of three neonicotinoid pesticide seed dressings for mass-flowering crops. We assessed the effectiveness of this policy in reducing the exposure risk to honeybees by collecting 130 samples of honey from bee keepers across the UK before (2014: N = 21) and after the moratorium was in effect (2015: N = 109). Neonicotinoids were present in about half of the honey samples taken before the moratorium, and they were present in over a fifth of honey samples following the moratorium. Clothianidin was the most frequently detected neonicotinoid. Neonicotinoid concentrations declined from May to September in the year following the ban. However, the majority of post-moratorium neonicotinoid residues were from honey harvested early in the year, coinciding with oilseed rape flowering. Neonicotinoid concentrations were correlated with the area of oilseed rape surrounding the hive location. These results suggest mass flowering crops may contain neonicotinoid residues where they have been grown on soils contaminated by previously seed treated crops. This may include winter seed treatments applied to cereals that are currently exempt from EU restrictions. Although concentrations of neonicotinoids were low (<2.0 ng g-1), and posed no risk to human health, they may represent a continued risk to honeybees through long-term chronic exposure.

Effects of insecticide application on parasitism rates of pollen beetle larvae (Brassicogethes aeneus (Fabricius)) by tersilochine parasitoids

Larval parasitoids can substantially reduce the population density of the pollen beetle [Brassicogethes aeneus (Fabricius), syn. Meligethes aeneus (Fabricius)]. The most abundant tersilochine parasitoids of pollen beetle are Tersilochus heterocerus, Phradis interstitialis and P. morionellus. The main activity of these parasitoids was observed in the period shortly before flowering to full flowering of oilseed rape. Insecticide applications during this period may have negative effects on parasitoids. In the present study, the effects of the insecticides Biscaya (a.i. thiacloprid), Mavrik (a.i. tau-fluvalinate) and Karate Zeon (a.i. lambda-cyhalothrin) applied during the bud or flowering stage of winter oilseed rape on parasitization of pollen beetle larvae by T. heterocerus were studied in 12 field trials at different locations in Germany in 2013–2015. The effects on parasitism by Phradis spp. were assessed in 2015. Parasitism of pollen beetle larvae by T. heterocerus was found in all field trials in all experimental years, but in most trials not before full flowering. Maximum percentage of parasitized larvae at different locations ranged between 3.4 and 16.8% in 2013, 8.3 and 22.4% in 2014 and from 11.1 to 29.1% in 2015. Levels of parasitism were not significantly different between the untreated control and insecticide treatments within each location. In contrast to T. heterocerus, Phradis spp. was not detected at all locations and not before flowering declining. In field trials at Lucklum and Puch, the maximum level of parasitism by Phradis spp. was 9.4 and 18.3%, respectively. No significant effect of insecticide application on parasitism by Phradis spp. was observed between the treatments. The results of this study showed that the insecticides used in the field trials did not affect parasitization of pollen beetle larvae by T. heterocerus and Phradis spp., regardless whether applied at the bud stage, at the beginning of flowering or full flowering.

A model to account for data dependency when estimating floral cover in different land use types over a season

We propose a model to consider data dependencies and assess spatial and temporal variability in land use specific floral coverage across landscapes. Data dependence arising from repeated measurements across the flowering season is taken into account using hierarchical Archimedean copulas, where the correlation is assumed to be stronger within seasonal periods than between periods. For each seasonal period, a bounded probability distribution is assigned to capture spatial variability in floral cover. The model uses a Bayesian approach and can assess land-use-specific floral covers by integrating experts judgments and field data. The model is applied to assess floral covers in four land use types in southern Sweden, where seasonal variability is captured by dividing the season into two periods according to winter oilseed rape flowering. Floral cover is updated using Markov Chain Monte Carlo sampling based on data from 16 landscapes and 2 years, with repeated measures available from each of the two seasonal periods. Our results indicate that considering data dependence improved the estimation of floral cover based on data observed during a season. Different copula families specifying multivariate probability distributions were tested, and no family had a consistently higher performance in the four tested land use types. Uncertainty in both mode and variability of floral cover was higher when data dependence were accounted for. Posterior modes of floral covers in semi-natural grassland were higher than in field edges, but both expert’s best guesses were higher than these estimates. This confirms previous findings in expert elicitation processes that experts may fail to discriminate extreme values on a bounded range. Floral cover in flower strips were estimated to be smaller/higher than semi-natural grasslands early/late in the season. The mode of floral cover in oil seed rape was estimated to be close to 100%, and higher than estimates provided by expert judgment. Floral covers for different land use classes are key parameters when quantifying floral resources at a landscape level whose assessments rely on both expert judgment and field measurements.