Search

International audience; The paradigm for all toxicological bioassays in the risk assessment of pesticide registration reflects the principle that experimental conditions should be controlled to avoid any other factors that may affect the endpoint measures. As honeybee colonies can be frequently exposed to bio-aggressors in real conditions, often concomitantly with pesticides, co-exposure to pesticide/bio-aggressors is becoming a concern for regulatory authorities. We investigated the effects of the neonicotinoid insecticide thiamethoxam on the homing performances of foragers emerging from colonies differentiated by health status (infestation with Varroa destructor mites, microsporidian parasite Nosema spp. and Deformed Wing Virus). We designed a homing test that has been recently identified to fill a regulatory gap in the field evaluations of sublethal doses of pesticides before their registration. We also assessed the effect of temperature as an environmental factor. Our results showed that the Varroa mite exacerbates homing failure (HF) caused by the insecticide, whereas high temperatures reduce insecticide-induced HF. Through an analytical Effective Dose (ED) approach, predictive modeling results showed that, for instance, ED level of an uninfested colony, can be divided by 3.3 when the colony is infested by 5 Varroa mites per 100 bees and at a temperature of 24°C. Our results suggest that the health status of honeybee colonies and climatic context should be targeted for a thorough risk assessment.

Measuring time-activity budgets over the complete individual lifespan is now possible for many animals with the recent advances of life-long individual monitoring devices. Although analyses of changes in the patterns of time-activity budgets have revealed ontogenetic shifts in birds or mammals, no such technique has been applied to date on insects.We tested an automated breakpoint-based procedure to detect, assess and quantify shifts in the temporal pattern of the flight activities in honey bees. We assumed that the learning and foraging stages of honey bees will differ in several respects, to detect the age at onset of foraging (AOF).Using an extensive dataset covering the life-long monitoring of 2,100 individuals, we compared the AOF outputs with the more conventional approaches based on arbitrary thresholds. We further evaluated the robustness of the different methods comparing the foraging time-activity budget allocations between the presumed foragers and confirmed foragers.We revealed a clear-cut learning-foraging ontogenetic shift that differs in duration, frequency, and time of occurrence of flights. Although AOF appeared to be highly plastic among bees, the breakpoint-based procedure seems better able to detect it than arbitrary threshold-based methods that are unable to deal with inter-individual variation.We developed theaofR-package including a broad range of examples with both simulated and empirical dataset to illustrate the simplicity of use of the procedure. This simple procedure is generic enough to be derived from any individual life-long monitoring devices recording the time-activity budgets of honey bees, and could propose new ecological applications of bio-logging to detect ontogenetic shifts in the behaviour of central-place foraging insects.

International audience; 1. Measuring time‐activity budgets over the complete individual lifespan is now possible for many animals with the recent advances of life‐long individual monitoring devices. Although analyses of changes in the patterns of time‐activity budgets have revealed ontogenetic shifts in birds or mammals, no such technique has been applied to date on insects. 2. We tested an automated breakpoint‐based procedure to detect, assess and quantify shifts in the temporal pattern of the flight activities in honey bees. We assumed that the learning and foraging stages of honey bees will differ in several respects, to detect the age at onset of foraging (AOF).3. Using an extensive dataset covering the life‐long monitoring of 1,167 individuals, we compared the AOF outputs with the more conventional approaches based on arbitrary thresholds. We further evaluated the robustness of the different methods comparing the foraging time‐activity budget allocations between the presumed foragers and confirmed foragers.4. We revealed a clear‐cut learning‐foraging ontogenetic shift that differs in duration, frequency, and time of occurrence of flights. Although AOF appeared to be highly plastic among bees, the breakpoint‐based procedure seems better able to detect it than arbitrary threshold‐based methods that are unable to deal with inter‐individual variation.5. We developed the aof R‐package including a broad range of examples with both simulated and empirical datasets to illustrate the simplicity of use of the procedure. This simple procedure is generic enough to be derived from any individual life‐long monitoring devices recording the time‐activity budgets, and could propose new ecological applications of bio‐logging to detect ontogenetic shifts in the behaviour of central‐place foragers.

Honeybees, major providers of pollination, are endangered in many areas. Embryo cryopreservation may be a very useful tool to maintain their genetic diversity. However, it is complex in insects, because embryos are chill sensitive and are surrounded by two protectant membranes, the chorion and vitelline. These membranes prevent penetration of cryoprotectant in the embryos. This study aimed to test different conditions of embryo preparation before cryopreservation, including low-frequency sonophoresis, a physical method of permeabilization, and passages through cryoprotectant solutions. Apis mellifera ligustica embryos were collected in artificial cell plugs 7.5 h after queens had been caged, in two different seasons (winter, spring) and were then incubated in vitro overnight (16.5 h). Embryos were individually sonicated and then incubated in three cryoprotectant baths (B1 = 10%, B2 = 20% and B3 = 40% of cryoprotectant) and quenched in liquid nitrogen. Artificial cell plugs and in vitro incubation device were efficient in producing future embryos hatching. Embryos stained ruby red with rhodamine B after sonophoresis treatment indicated that low-frequency ultrasound had permeabilized embryos. According to the treatment, different significant hatching rates were obtained after sonophoresis (up to 25%). After three cryoprotectant incubations, best hatching rates were obtained after 10 min in B1 and B2, and 40 s in B3. These results show that sonophoresis is an efficient tool to permeabilize the chorion and vitelline membrane of the day one honeybee embryo allowing a hatching rate of more than 20%. They also show that the season is an important variability factor.

International audience; Modern agriculture often involves the use of pesticides to protect crops. These substances are harmful to target organisms (pests and pathogens). Nevertheless, they can also damage non-target animals, such as pollinators and entomophagous arthropods. It is obvious that the undesirable side effects of pesticides on the environment should be reduced to a minimum. Western honey bees (Apis mellifera) are very important organisms from an agricultural perspective and are vulnerable to pesticide-induced impacts. They contribute actively to the pollination of cultivated crops and wild vegetation, making food production possible. Of course, since Apis mellifera occupies the same ecological niche as many other species of pollinators, the loss of honey bees caused by environmental pollutants suggests that other insects may experience a similar outcome. Because pesticides can harm honey bees and other pollinators, it is important to register pesticides that are as selective as possible. In this manuscript, we describe a selection of methods used for studying pesticide toxicity/selectiveness towards Apis mellifera. These methods may be used in risk assessment schemes and in scientific research aimed to explain acute and chronic effects of any target compound on Apis mellifera.

La combinaison de la mortalité et de colonies non productrices en sortie d’hiver est responsable d’un taux de mortalité représentant près d’un tiers du cheptel. Nous nous sommes intéressés aux conditions environnementales des colonies d’abeilles mellifères à cette période cruciale de pré-hivernage. Une solution technique spécifique a été testée pour étudier l’influence de l’environnement sur la période d’hivernage des colonies. C’est grâce à une double approche d’accompagnement des acteurs et expérimentale s’appuyant sur une implication forte des agriculteurs et apiculteurs de la Beauce, que les partenaires du projet InterAPI mettent en évidence l’intérêt d’un aménagement du territoire qui intègre des cultures intermédiaires mellifères (CIM) favorables aux colonies. Ils identifient les espèces candidates et leurs caractéristiques grâce à deux outils d’aide à la gestion de cette interculture., The rates of honeybee colony winter losses remain very high describing mortalities and non-producing colonies after wintering represents nearly a third of the producing colonies. We were interested in environmental conditions of honeybee colonies at this crucial time. A technical solution has been tested and specifically to study environment influence on the wintering period of the colonies. Through a dual approach of co-construction and experimental, based on a strong involvement of farmers and beekeepers in Beauce region, partners of InterAPI project highlight the interest of a landscape management which includes melliferous catch crops. They identify candidate species and their characteristics using two tools helping the management of catch crops.

International audience; Originally, a method to rear worker honey bee larvae in vitro was introduced into the field of bee biology to analyse honey bee physiology and caste development. Recently, it has become an increasingly important method in bee pathology and toxicology. The in vitro method of rearing larvae is complex and can be developed as an art by itself, especially if the aim is to obtain queens or worker bees which, for example, can be re-introduced into the colony as able members. However, a more pragmatic approach to in vitro rearing of larvae is also possible and justified if the aim is to focus on certain pathogens or compounds to be tested. It is up to the researcher(s) to decide on the appropriate experimental establishment and design. This paper will help with this decision and provide guidelines on how to adjust the method of in vitro rearing according to the specific needs of the scientific project.

Honey bee diet surveys require an accurate knowledge of the pollen supply and a rapid counting method for microscopic analyses. Referring to the literature, we aimed at reducing the number of pollen grains counted in order to decrease the time spent for each sample. For this, we compared counts on whole transects to alternative methods of counting by sub-sampling, using the non-acetolysed palynological method. For each pellet sample, a drop of a homogenized suspension was dried, degreased, and mounted onto a slide dressed with glycerol gelatin. The counting was performed through a digital camera fitted on a microscope. The study was carried out in two phases. Phase 1 was a test of slide homogeneity, carried out on a 10-slide set with one replicate. For each slide, we compared an exhaustive count of each present taxon on a whole transect divided in four quarters. Phase 2 was a search for an alternative counting method. The work was performed over the first six samples with replicates retaining exactly the same transect, but counting only one microscope field in three, then four, and finally one in five. Data analyses were carried out with Chi-square tests on taxa that were present in more than 5% of the sample. Phase 1 showed some cases of heterogeneity in microscope slides, leading to an error hazard when counting in a continuous mode up to a defined grain number. In phase 2, the comparison of alternative countings to full transects verified the linearity of the counting results. Suitable results were given by the reading method “one in three”. We improved the accuracy of this method for the particular case of samples containing large pollen grains, e.g., Zea mays, which are unevenly disseminated on the slide.; La evaluación de la dieta de la abeja de la miel requiere un conocimiento exacto del suministro de polen y un método de conteo rápido para los análisis microscópicos. En referencia a la literatura, tuvimos como objetivo reducir el número de granos de polen contados con el fin de disminuir el tiempo empleado para cada muestra. Para ello, se compararon los recuentos en transectos enteros con otros métodos de conteo mediante submuestreos usando el método palinológico no acetolisado. Para cada muestra de precipitado, se secó una gota de una suspensión homogeneizada, desengrasada y montada en un portaobjetos impregnado con gelatina de glicerol. El recuento se llevó a cabo a través de una cámara digital montada en un microscopio. El estudio se llevó a cabo en dos fases. Fase 1 fue una prueba de homogeneidad del portaobjetos, llevado a cabo en una serie de 10 portaobjetos con un replicado. Para cada portaobjetos, se comparó un recuento exhaustivo de cada taxón presente en todo un transecto dividido en cuatro cuartos. Fase 2 fue la búsqueda de un método de recuento alternativo. El trabajo se llevó a cabo en las primeras seis muestras con réplicas usando exactamente el mismo transecto, pero contando sólo un campo al microscopio de tres, luego cuatro, y finalmente uno de cada cinco. Los análisis de datos se llevaron a cabo con las pruebas de Chi-cuadrado sobre taxa que estaban presentes en más de 5% de la muestra. Fase 1 mostró algunos casos de heterogeneidad en los portaobjetos de microscopio, dando lugar a un riesgo de error cuando se cuentan en un modo continuo hasta un número definido de grano. En la fase 2, la comparación de recuentos alternativos para transectos completos verificó la linealidad de los resultados del recuento. Los resultados más adecuados se obtuvieron con el método de lectura “uno de cada tres”. Hemos mejorado la exactitud de este método para el caso particular de las muestras que contienen grandes granos de polen, por ejemplo, Zea mays, que se difunde de manera desigual en el portaobjetos.

International audience; Recent studies succeeded in developing a method to automatically record honeybees going in and out of the hive. Honeybees were individualized with radio frequency identification (RFID) tags glued onto their dorsal surface and detected at the hive entrance by readers emitting high-frequency (HF) radio waves. In this work we search for a possible adverse effect of HF on honeybees' survival. Eight-day-old honeybees were exposed to HF (13.56 MHz) or ultra-high-frequency (UHF, 868 MHz) radio waves for 2 h split into ON and OFF periods. The ON/OFF ratio was 1:3 (OFF duration 3, 90, 180, 370 and 360 s) or 1:5 (OFF duration 300 s). Dead individuals were counted every day, and the cumulative mortality rates of exposed and non-exposed honeybees were compared 7 days after exposure. Out of the five experimental conditions, we observed an increase in mortality in two conditions, once after HF and once after UHF exposure, with OFF duration of 5 min or more. We then recommend limiting exposure of honeybees to radio waves to less than 2 h per day, and we conclude that the RFID parameters, like those we used in the field for monitoring hive activity, present no adverse effects for honeybees.

International audience; Pollen resources may become a constraint for the honey bee in cereal farming agrosystems and thus influence honey bee colony development. This survey intended to increase knowledge on bee ecology in order to understand how farming systems can provide bee forage throughout the year. We conducted a 1-year study to investigate the flower range exploited in an agrarian environment in western France, the physico-chemical composition of honey bee-collected pollen, the territorial biodiversity visited by the bee at different periods, and the relationships between these three datasets. Palynological analyses showed the importance of maize among crop pollens and that of weeds during the food shortage period. Pollen protein varied from 16% to 29% and lipids from 7% to 24%. The contribution of different habitats to pollen harvest, was from crops (62%), woods (32%), grasslands (4%), and gardens (1%).

Losses of foraging bees are sometimes attributed to altered flight pattern between a meliferous plant treated with an insecticide and the hive. Only a limited number of studies has investigated the impact of pesticides on homing flight due to the difficulty of measuring the flight time between the food source and the hive. Monitoring the flights of the foraging bees needs their individual identification. The number of bees monitored simultaneously and the time span during which observations can be made limit most of the monitoring techniques. However, techniques of automatic tracking and identification of individuals have the potential to revolutionize the study of the ecotoxicological effects of xenobiotics on the bee behaviors. Radio Frequency Identification (RFID) offer numerous advantages such as an unlimited number of codes, a large number of simultaneous recording, and a quick reading, especially through materials (e.g., wood). The aim of this study was to show how the RFID device can be used to study the effects of pesticides on both the behavioral traits and the lifespan of bees. In this context, we have developed a method under tunnel to automatically record the displacements of foragers individualized with RFID tags and to detect the alteration of the flight pattern between an artificial feeder and the hive. Fipronil was selected as test substance due to the lack of information on the effects of this insecticide on the foraging behavior of free-flying bees. We showed that oral treatment of 0.3 ng of fipronil per bee (LD50/20) reduced the number of foraging trips. The strengths of our approach were briefly discussed.

International audience; European governments have banned the use of three common neonicotinoid pesticides due to insufficiently identified risks to bees. This policy decision is controversial given the absence of clear consistency between toxicity assessments of those substances in the laboratory and in the field. Although laboratory trials report deleterious effects in honeybees at trace levels, field surveys reveal no decrease in the performance of honeybee colonies in the vicinity of treated fields. Here we provide the missing link, showing that individual honeybees near thiamethoxam-treated fields do indeed disappear at a faster rate, but the impact of this is buffered by the colonies' demographic regulation response. Although we could ascertain the exposure pathway of thiamethoxam residues from treated flowers to honeybee dietary nectar, we uncovered an unexpected pervasive co-occurrence of similar concentrations of imidacloprid, another neonicotinoid normally restricted to non-entomophilous crops in the study country. Thus, its origin and transfer pathways through the succession of annual crops need be elucidated to conveniently appraise the risks of combined neonicotinoid exposures. This study reconciles the conflicting laboratory and field toxicity assessments of neonicotinoids on honeybees and further highlights the difficulty in actually detecting non-intentional effects on the field through conventional risk assessment methods.

[br/] [b]Background[/b][br/] Juvenile hormone (JH) plays an important role in honeybee development and the regulation of age-related division of labor. However, honeybees can be exposed to insect growth regulators (IGRs), such as JH analogs developed for insect pest and vector control. Although their side effects as endocrine disruptors on honeybee larval or adult stages have been studied, little is known about the subsequent effects on adults of a sublethal larval exposure. We therefore studied the impact of the JH analog pyriproxyfen on larvae and resulting adults within a colony under semi-field conditions by combining recent laboratory larval tests with chemical analysis and behavioral observations. Oral and chronic larval exposure at cumulative doses of 23 or 57 ng per larva were tested.[br/] [br/] [b]Results[/b][br/] Pyriproxyfen-treated bees emerged earlier than control bees and the highest dose led to a significant rate of malformed adults (atrophied wings). Young pyriproxyfen-treated bees were more frequently rejected by nestmates from the colony, inducing a shorter life span. This could be linked to differences in cuticular hydrocarbon (CHC) profiles between control and pyriproxyfen-treated bees. Finally, pyriproxyfen-treated bees exhibited fewer social behaviors (ventilation, brood care, contacts with nestmates or food stocks) than control bees.[br/] [br/] [b]Conclusion[/b][br/] Larval exposure to sublethal doses of pyriproxyfen affected several life history traits of the honeybees. Our results especially showed changes in social integration (acceptance by nestmates and social behaviors performance) that could potentially affect population growth and balance of the colony.

Bad News for Bees Neonicotinoid insecticides were introduced in the early 1990s and have become one of the most widely used crop pesticides in the world. These compounds act on the insect central nervous system, and they have been shown to be persistent in the environment and in plant tissues. Recently, there have been controversial connections made between neonicotinoids and pollinator deaths, but the mechanisms underlying these potential deaths have remained unknown. Whitehorn et al. (p. 351 , published online 29 March) exposed developing colonies of bumble bees to low levels of the neonicotinoid imidacloprid and then released them to forage under natural conditions. Treated colonies displayed reduced colony growth and less reproductive success, and they produced significantly fewer queens to found subsequent generations. Henry et al. (p. 348 , published online 29 March) documented the effects of low-dose, nonlethal intoxication of another widely used neonicotinoid, thiamethoxam, on wild foraging honey bees. Radio-frequency identification tags were used to determine navigation success of treated foragers, which suggested that their homing success was much reduced relative to untreated foragers.

This chapter provides an overview of existing toxicity tests and their strengths and weaknesses, and discusses proposed modifications to existing studies, or additional studies that could address limitations in the current battery of studies. In the European Union (EU), regulatory authorities may require a bee brood feeding test to assess potential hazard of a pesticide on honey bee larvae. The chapter reports toxicity testing with some species of adult non-Apis bees with some frequency. It discusses some of the methods that have been developed to measure the potential sublethal effects of pesticides on honey bees. Laboratory toxicity tests are currently available for evaluating the potential effects of chemicals on bees. Laboratory-based studies will likely continue to focus on individual test organisms; and, although laboratory-based toxicity testing has historically focused on mortality, tests are evolving to provide insight on sublethal effects such as impaired behavior.

International audience; In Central Western France, as in many other areas, traditional apiculture has been replaced by more intensive practices to compensate for colony losses andcurrent decreasing honey yields. One neglected aspect concerns the choice by professional beekeepers of apiary sites in intensive agrosystems, with regard to landscape features, a choice which appears to be largely empirical. ECOBEE is a colony monitoring scheme specifically ntended to provide beekeepers and researchers with basic ecological data on honeybees in intensive agrosystems, as well as colony population dynamics. ECOBEE was launched in 2008 as a long-term ecological project with three specific aims: 1. to monitor seasonal and inter-annual population dynamic parameters of honeybee colonies in a heterogeneous farming system; 2. to provide relevant and robust datasets to test specific hypotheses about bees such as the influence of landscape planning, agricultural inputs or human pressure; and 3. to offer opportunities for assessing the effectiveness of agro-environmental schemes or the effects of changes in agricultural policies on honey bee wellbeing. Here we present an overview of ECOBEE, the type of datasets collected over the first four years of monitoring, and their possible application and use. We found that colony dynamics were largely influenced by the phenology of the main mass-flowering crops foraged by bees, namely oilseed rape and sunflowers. Furthermore, we detected a sharp food shortage period in late spring between the flowering of oilseed rape and sunflowers, possibly temporarily constraining colony sustainability. We further discuss the research perspectives offered by ECOBEE, especially with regard to spatial ecotoxicology.

Zone Atelier Plaine & Val de Sèvre; International audience; The risk assessment of plant protection products on pollinators is currently based on the evaluation of lethal doses through repeatable lethal toxicity laboratory trials. Recent advances in honeybee toxicology have, however, raised interest on assessing sublethal effects in free-ranging individuals. Here, we show that the sublethal effects of a neonicotinoid pesticide are modified in magnitude by environmental interactions specific to the landscape and time of exposure events. Field sublethal assessment is therefore context dependent and should be addressed in a temporally and spatially explicit way, especially regarding weather and landscape physiognomy. We further develop an analytical Effective Dose (ED) framework to help disentangle context-induced from treatment-induced effects and thus to alleviate uncertainty in field studies. Although the ED framework involves trials at concentrations above the expected field exposure levels, it allows to explicitly delineating the climatic and landscape contexts that should be targeted for in-depth higher tier risk assessment.

Chapitre 9; Honey bees are beneficial insects playing a key role in pollinating wild plants and crop plants. Unfortunately, during their foraging activity they can be exposed to pesticides and other xenobiotics. The members of the colony can also be poisoned indirectly by contaminated food and water brought back to the hive by foragers. While the assessment of the potential adverse effects of a xenobiotic on individual bees can be easily done by using normalized laboratory tests, toxicity estimation at the population level suffers from technical difficulties and is costly. Fortunately, population modeling is increasingly used to overcome this problem of transition from the individual to the population level. In this context, an agent-based model, called SimBeePop, was designed for predicting the long-term effects of man-made chemicals on honey bee populations. After a detailed description of the structure of the model, its performances were estimated on pyriproxyfen, a juvenile hormone mimic. To do so, the physicochemical properties, environmental fate, use, and toxicity of this insecticide to honey bees were reviewed in order to elaborate realistic scenarios of contamination. Application of these scenarios in SimBeePop reveal that while pyriproxyfen is classified as moderately toxic or not toxic to bees under current regulations, it can induce significant adverse effects on bee populations at sublethal concentrations

International audience; A tight control of juvenile hormone (JH) titre is crucial during the life cycle of a holometabolous insect. JH metabolism is made through the action of enzymes, particularly the juvenile hormone esterase (JHE). Trifluoromethylketones (TFKs) are able to inhibit this enzyme to disrupt the endocrine function of the targeted insect. In this context, a set of 96 TFKs, tested on Trichoplusia ni for their JHE inhibition, was split into a training set (n = 77) and a test set (n = 19) to derive a QSAR model. TFKs were initially described by 42 CODESSA (Comprehensive Descriptors for Structural and Statistical Analysis) descriptors, but a feature selection process allowed us to consider only five descriptors encoding the structural characteristics of the TFKs and their reactivity. A classical and spline regression analysis, a three-layer perceptron, a radial basis function network and a support vector regression were experienced as statistical tools. The best results were obtained with the support vector regression (r(2) and r(test)(2) = 0.91). The model provides information on the structural features and properties responsible for the high JHE inhibition activity of TFKs.

International audience; Cresswell and Thompson have suggested an elegant way to improve honey bee colony simulations when forecasting the fate of colonies exposed to pesticides. Following their recommendations, we rescaled the model on a sound empirical data set. The adjusted forecast is bleaker than their tentative scenario.

SUMMARYBombus terrestris queens which had been overwintered in artificial conditions were transferred to small wooden boxes in a climate room at 28°C and 65% RH; the bees were supplied with food and subjected to one of four photoperiodic regimes (L24: DO; L8: D16; L16: D8; LO: D24. The photoperiodic regimes were applied until the queens had produced 10–15. workers, after which colonies were transferred from the small initiation boxes to larger ones to allow nests to increase in colony size. The proportion of queens in each treatment which founded colonies ranged from 42% to 61 %, but no significant difference was detected between photoperiodic regimes. Delays to oviposition were significantly shorter in the L8: D16 regime compared with constant dark and constant light: 33.4 ± 4.9 days, 47.3 ± 4.8 days and 58.9 ± 6.7 days respectively. In the L16: D8 regime the delay (42.4 ± 5.6 days) was not significantly different from that in the L8: D16 regime. The period from the start of brooding attitude to oviposit...

The use of agent-based models (ABMs) is steadily increasing in all the disciplines including environmental chemistry and toxicology. This growth is mainly driven by their ability to address problems that conventional modelling techniques cannot, such as the change of scale or the emergence of unanticipated phenomena resulting from interactions between their constitutive goal-directed agents. After a brief introduction on the basic principles of agent-based modelling and the presentation of selected case studies, the main software resources available on the Internet are presented. An attempt is made to estimate the complexity of these tools versus their potentialities and flexibility.

The nutritive value of pollen blends purchased by bumble bee producers from beekeepers is a key factor of successful mass rearing. We have already devised a method for quality ranking of pollen diets. It was a 1-mo bioassay using queenless micro-colonies of three callow workers (Bombus terrestris L.; Apidae: Bombinae). In the current study, we tested three pollen diets through the micro-colony method and compared the results to the development of queenright colonies supplied with the same diets. The three diets were "A," a spring blend with a protein rate of 15.7% and a dominance of Corylus avellana L.(46%) and Buxus sempervivens L. (35%); "B," a summer assemblage with alower crude protein content (14.4%), with a dominance of Helianthus annuus L. (37%), Zea mays L. (35%), and Poaceae (21%); and "C," a 50/50 mixture by weight of A and B, with a crude protein content of 15.8%. In micro-colonies, the more sensitive parameter for diet ranking was the mean weight of a larva, whereas in queenright colonies, the discrimination between treatments was enabled by considering the body size of new queens (weight and length of the radial cell) and the slope of the sigmoidal curve of the pollen consumption at the inflection point reflecting brood growth. Both testing methods assigned the lower rank to diet B compared with diet A. Despite the closeness of the three diets in terms of nitrogen content, we concluded that micro-colonies were a good estimate of colony development when nutritive value of pollen was tested.

International audience; Laboratory trials were performed at 27 °C on micro-colonies comprised of three Bombus terrestris workers. They were fed with syrup and pollen paste ad libitum. The micro-colonies were terminated on the 14th day after egg-laying. Two bioassays tested the nutritive value of 6 pure pollens and 9 commercial pollen mixes on bumblebee larvae. Among 10 criteria tested, the most sensitive to the different pollens were the mean weight of larvae and the rate of discarded larvae. Differentiation between treatments was easier with single pollens that ranged from 14.4% to 24.9% crude protein for Helianthus and Castanea respectively, than with mixes that ranged from 12.9% to 17.6%. The best performance ranking was assigned to Castanea, Papaver and Rubus, which produced larvae weighing 110-150 mg, the lowest to Helianthus and Cistus which resulted in larvae of 20-50 mg. The largest larvae (240 mg) were produced with the mix at 96% Brassica and 15.9% protein and the smallest with the mix at the lowest protein content (12.9%) assembling Picris, Hedera, Amaranthus, Solanum, Helianthus and graminaceae.

Nous avons étudié les effets de populations françaises du puceron du pois (Acyrthosiphon pisum) de trois origines (Champagne, Languedoc, Poitou), prélevées dans des luzernières lors de diverses saisons et années, sur la résistance du cultivar CUF 101 de luzerne (Medicago sativa). Les populations aphidiennes de chaque origine ont été caractérisées par quatre marqueurs biochimiques, à deux reprises : lors des prélèvements réalisés au champ, et lors des tests d’estimation de la résistance réalisés en conditions contrôlées. Nous avons relevé 28 % de diminution de la variabilité génétique aphidienne (exprimée par les marqueurs biochimiques et leur couleur) entre ces deux séries. Dans les populations aphidiennes utilisées lors des tests, une faible diversification, estimée par l’indice de fixation FST se manifeste entre champs d’une même origine géographique, entre années et entre saisons. Cette diversification est plus marquée entre les zones géographiques distantes de 500 km. Cette variabilité des populations aphidiennes n’a pas d’effet majeur sur le niveau de résistance du cultivar CUF 101, puisque ce n’est que dans moins de 3 % des cas que son niveau de résistance élevé décroît de façon nette à un niveau intermédiaire. La discussion porte sur les effets de la constitution génétique des souches aphidiennes dans l’estimation de la résistance variétale., We estimated the level of resistance of CUF 101 cv of alfalfa (Medicago sativa) to French populations of the pea aphid (Acyrthosiphon pisum) collected from alfalfa fields of three different regions (Champagne, Languedoc, Poitou), from various seasons and years. Allozymes from individual aphids of each origin were used as markers to examine the genetic structure of aphid populations on two occasions: when populations were collected in the field and when resistance tests were conducted under controlled conditions. A decrease of 28% in aphid genetic variability (biochemical markers and color) was noticed between these two occasions. The aphid populations used in the resistance tests were weakly differentiated (low FST) between fields of the same region, seasons or years in each region, but were differentiated regionally (higher FST). Aphid variability has low consequences on the resistance of CUF 101. In less than 3% of the resistance tests a distinct lowering from resistant to intermediate level of resistance was observed. We discuss the benefit of understanding genetic variability of aphid populations when developing plant resistance programs.

National audience

Dossier de Presse INRA; Un monde sans abeilles ? N’y pensons pas ! Bien sûr, les produits de la ruche, miel, pollen, cire, nous manqueraient. Mais surtout, ces super-pollinisateurs sont indispensables à l’agriculture. Si on parle de tonnage, 35% de ce que nous mangeons dépend directement de leur travail silencieux. Si on parle de diversité, c’est 84% des espèces cultivées en Europe et plus de 80% des espèces sauvages qui ont besoin de leurs pattes et de leur toison pour s’échanger du pollen et se reproduire. Alors, seriez-vous prêt à vous passer de la plupart des fruits et légumes ?

Master; The honeybee have an essential economic importance in agronomy, however it is exposed to many pesticides. The pesticides’s impact is underestimated in the bee’s excess of mortality phenomenon in particular because of their sublethal effects which are still poorly evaluated. The objective of this study is to identify the effects of boscalid and/or sulfoxaflor on life-history traits of workerbees during larval and/or adult exposure at concentrations likely to be found in the environment. The workers were tagged with "Radio Frequency IDentification" microchips and then introduced into a hive to measure their activities using the following variables : age of first exit, number and duration trips. The study reveals that boscalid leads the highest mortality. Bee’s exposure to sulfoxaflor increases the duration of flights and delays the age of first exit. The products coexposition shows a potential antagonistic effect on exit duration. Unlike boscalid, sulfoxaflor induces sublethal effects similar to some neonicotinoids. Given the pesticides coexposition’s results, detoxification phenomenon can be suggested. This study provides a first framework of reference for assessing sublethal effects of bees to a pesticide mixture using RFID tools.; L’abeille domestique a une importance économique capitale en agronomie, pourtant elle est exposée à de nombreux pesticides. L’impact des pesticides est sous-estimé dans le phénomène de surmortalité des abeilles notamment en raison de leurs effets sublétaux qui sont encore mal évalués. L’objectif de cette étude est d’identifier les effets du boscalid et/ou du sulfoxaflor sur les traits d’histoire de vie des ouvrières lors d’exposition larvaire et/ou adulte à des concentrations susceptibles d’être retrouvées dans l’environnement. Les ouvrières ont ensuite été marquées avec des puces « Radio Frequency IDentification » (RFID) puis introduites dans une ruche afin de mesurer leurs activités par le biais des variables suivantes : âge de première sortie, nombre et durée des sorties. L’étude révèle que le boscalid induit la mortalité la plus forte. L’exposition des abeilles au sulfoxaflor augmente la durée des vols et retarde l’âge de première sortie. La coexposition des produits montre un potentiel effet antagoniste sur la durée des sorties. Contrairement au boscalid, le sulfoxaflor induit des effets sublétaux similaires à certains néonicotinoïdes. Des phénomènes de détoxification peuvent être suggérés au vue des résultats obtenus concernant la coexposition des pesticides. Cette étude offre un premier cadre de référence pour évaluer les effets sublétaux d’abeilles à un mélange de pesticides grâce à des outils RFID.

Licence; Les pollinisateurs jouent un rôle très important en agriculture. Mais avec la persistance dans l’environnement des pesticides énormément utilisés en agriculture, de nombreux organismes non-ciblés sont exposés de manière chronique. C’est en particulier le cas pour les pollinisateurs, au point de jouer un rôle important dans le déclin des populations. Ici, nous nous intéressons à l’effet du Boscalid (un fongicide) et du Sulfoxaflor (un insecticide) sur le développement des glandes hypopharyngiennes de l’abeille européenne (Apis mellifera), suite à une exposition à des doses réalistes à l’état larvaire et adulte. Les glandes hypopharyngiennes sont situées dans la tête de l’abeille, elles sont principalement développées chez les jeunes adultes. Ces glandes permettent, entre autre, de produire la gelée royale utilisée pour nourrir les larves. Une perturbation dans ces glandes pourrait avoir un effet négatif sur la colonie. Les abeilles utilisées ont été élevées in vitro. La quantité de sulfoxaflor utilisé est de 10.6ng/larve et 0,034 μg/jour/abeille adulte. Pour le boscalid la quantité est de 15.9ng/larve et de 0,103 μg/jours/abeille adulte. Pour connaître le développement des glandes nous réalisons un dosage total des protéines par la méthode de Bradford. Lors de notre élevage nous avons observé une forte mortalité dans plusieurs modalités. Les doses utilisées pour l’exposition se trouvent au-dessus de la dose sublethal. Notamment pour les modalités avec les adultes exposées au sulfoxaflor qui ont eu 100 % de mortalité, dont plus 60 % à l’état adulte, a cause d’une dose égale au double de la DL50. Le dosage des protéines n’a pas donné de différences significatives de l’état des glandes hypopharyngiennes. Mais on retrouve une tendance, avec des glandes plus petites lorsque l’exposition se fait chez les adultes. Mais la mortalité chez les abeilles adultes exposées au sulfoxaflor, n’a pas permis de confirmer la tendance.

Master; In the last ten years honey bee (Apis mellifera) colonies have been in decline. There are multiple causes that contribute to that rapid downtrend. Among them are pests and pathogens, land-use intensification, habitat loss and fragmentation. In most of the cases, the consequences of co-exposition are unknown as only few studies addressed these questions so far. Here we would like to investigate the impact of co-expositon between a pathogen and a neonicotinoid on honey bee survival and learning performances. Yet all the studies about the influence of pesticides on learning and memory abilities are conducted on honey bees that were exposed to pesticide after emergence. But it is known that neonicotinoids are also stored inside the hives in pollen, nectar and brood is exposed to it. In our work we exposed honey bee larvae to American Foulbrood and to sub-lethal doses of Thiamethoxam (chronic exposure). First we hypothesise that the application of two treatments may have synergistic effect and induce higher mortality rates on larvae. We also tested the impact of this co-exposition, during the larval stage, on impairment of learning and memory abilities as well as the social behaviour of the honey bee workers. We used the standard olfactory conditioning procedure that is based on Proboscis Extension Response (PER) to study the changes in learning and memory abilities caused by the co-exposition effect.

Jusqu’à ce jour, seuls des acides gras de synthèse testés individuellement avaient montré une action antibactérienne vis-à-vis de la loque. Notre étude montre que les lipides extraits et les acides gras obtenus à partir des pollens ont aussi une action antibactérienne à des degrés variables selon l‘origine botanique, la nature et les proportions des constituants lipidiques. Les pollens qui ont donné les meilleures performances sur la bactérie responsable de la loque sont les pollens représentés majoritairement par le coquelicot, cornouiller et tournesol. Le moins performant a été celui représenté par l’aubépine. L’analyse physico chimique des pollens est complexe, en particulier pour l’extraction des lipides et nécessite de récupérer des composés intacts pour évaluer par la suite leurs propriétés. Nos tests larvaires n’ont pas montré d’effet protecteur des extraits, qui se sont même plutôt montrés toxiques. Les performances des abeilles adultes soumises à un pathogène en présence d’extraits lipidiques de pollen n’ont pas été supérieures aux témoins. De même, nous n’avons pas observé d’influence de la diversité florale sur un indicateur de défenses immunitaires.

Licence; La pollinisation par les bourdons de cultivar sous serre est une activité qui est amenée à s'étendre considérablement au cours des années à venir. Pour cela, il est primordial de maîtriser les paramètres nécessaires à l'élevage des bourdons en captivité. La composition de l'alimentation donnée aux reines à leur sortie de diapause dans les élevages, doit correspondre à leurs besoins. Pour cela nous avons prélevé des reines de Bombus terrestris dans la nature, et identifié les grains de pollen consommés et digérés. Les résultats obtenus au cours de cette étude montrent : - d'une part, que la reine n'est pas opportuniste quant au choix de sa nourriture. Elle consomme, dans la période précédant la nidification, préférentiellement des fleurs de Prunus, Salix et Brassica avec une large prédominance de Prunus. - D'autre part, que l'alimentation d'élevage, composée essentiellement de Salix, ne correspond pas à l'alimentation naturelle.