Chronic oral exposure to field-realistic pesticide combinations via pollen and nectar : effects on feeding and thermal performance in a solitary bee

Pesticide use is one of the main causes of pollinator declines in agricultural ecosystems. Traditionally, most laboratory studies on bee ecotoxicology test acute exposure to single compounds. However, under field conditions, bees are often chronically exposed to a variety of chemicals, with potential synergistic effects. We studied the effects of field-realistic concentrations of three pesticides measured in pollen and nectar of commercial melon fields on the solitary bee Osmia bicornis L. We orally exposed females of this species throughout their life span to 8 treatments combining two neonicotinoid insecticides (acetamiprid, imidacloprid) and a triazole fungicide (myclobutanil) via pollen and sugar syrup. We measured pollen and syrup consumption, longevity, ovary maturation and thermogenesis. Pesticide intake was three orders of magnitude higher via syrup than pollen. At the tested concentrations, no synergistic effects emerged, and we found no effects on longevity and ovary maturation. However, all treatments containing imidacloprid resulted in suppressed syrup consumption and drastic decreases in thoracic temperature and bee activity. Our results have important implications for pesticide regulation. If we had measured only lethal effects we would have wrongly concluded that the pesticide combinations containing imidacloprid were safe to O. bicornis. The incorporation of tests specifically intended to detect sublethal effects in bee risk assessment schemes should be an urgent priority. In this way, the effects of pesticide exposure on the dynamics of bee populations in agroecosystems will be better assessed

Bees exposed to climate change are more sensitive to pesticides

Altres ajuts: acords transformatius de la UABBee populations are exposed to multiple stressors, including land-use change, biological invasions, climate change, and pesticide exposure, that may interact synergistically. We analyze the combined effects of climate warming and sublethal insecticide exposure in the solitary bee Osmia cornuta. Previous Osmia studies show that warm wintering temperatures cause body weight loss, lipid consumption, and fat body depletion. Because the fat body plays a key role in xenobiotic detoxification, we expected that bees exposed to climate warming scenarios would be more sensitive to pesticides. We exposed O. cornuta females to three wintering treatments: current scenario (2007-2012 temperatures), near-future (2021-2050 projected temperatures), and distant-future (2051-2080). Upon emergence in spring, bees were orally exposed to three sublethal doses of an insecticide (Closer, a.i. sulfoxaflor; 0, 4.55 and 11.64 ng a.i./bee). We measured the combined effects of wintering and insecticide exposure on phototactic response, syrup consumption, and longevity. Wintering treatment by itself did not affect winter mortality, but body weight loss increased with increasing wintering temperatures. Similarly, wintering treatment by itself hardly influenced phototactic response or syrup consumption. However, bees wintered at the warmest temperatures had shorter longevity, a strong fecundity predictor in Osmia. Insecticide exposure, especially at the high dose, impaired the ability of bees to respond to light, and resulted in reduced syrup consumption and longevity. The combination of the warmest winter and the high insecticide dose resulted in a 70% longevity decrease. Smaller bees, resulting from smaller pollen-nectar provisions, had shorter longevity suggesting nutritional stress may further compromise fecundity in O. cornuta. Our results show a synergistic interaction between two major drivers of bee declines, and indicate that bees will become more sensitive to pesticides under the current global warming scenario. Our findings have important implications for pesticide regulation and underscore the need to consider multiple stressors to understand bee declines

Biochemical responses, feeding and survival in the solitary bee Osmia bicornis following exposure to an insecticide and a fungicide alone and in combination

In agricultural ecosystems, bees are exposed to combinations of pesticides that may have been applied at different times. For example, bees visiting a flowering crop may be chronically exposed to low concentrations of systemic insecticides applied before bloom and then to a pulse of fungicide, considered safe for bees, applied during bloom. In this study, we simulate this scenario under laboratory conditions with females of the solitary bee, Osmia bicornis L. We studied the effects of chronic exposure to the neonicotinoid insecticide, Confidor® (imidacloprid) at a realistic concentration, and of a pulse (1 day) exposure of the fungicide Folicur® SE (tebuconazole) at field application rate. Syrup consumption, survival, and four biomarkers: acetylcholinesterase (AChE), carboxylesterase (CaE), glutathione S-transferase (GST), and alkaline phosphatase (ALP) were evaluated at two different time points. An integrated biological response (IBRv2) index was elaborated with the biomarker results. The fungicide pulse had no impact on survival but temporarily reduced syrup consumption and increased the IBRv2 index, indicating potential molecular alterations. The neonicotinoid significantly reduced syrup consumption, survival, and the neurological activity of the enzymes. The co-exposure neonicotinoid-fungicide did not increase toxicity at the tested concentrations. AChE proved to be an efficient biomarker for the detection of early effects for both the insecticide and the fungicide. Our results highlight the importance of assessing individual and sub-individual endpoints to better understand pesticide effects on bees

Biochemical responses, feeding and survival in the solitary bee Osmia bicornis following exposure to an insecticide and a fungicide alone and in combination

In agricultural ecosystems, bees are exposed to combinations of pesticides that may have been applied at different times. For example, bees visiting a flowering crop may be chronically exposed to low concentrations of systemic insecticides applied before bloom and then to a pulse of fungicide, considered safe for bees, applied during bloom. In this study, we simulate this scenario under laboratory conditions with females of the solitary bee, Osmia bicornis L. We studied the effects of chronic exposure to the neonicotinoid insecticide, Confidor (R) (imidacloprid) at a realistic concentration, and of a pulse (1 day) exposure of the fungicide Folicur (R) SE (tebuconazole) at field application rate. Syrup consumption, survival, and four biomarkers: acetylcholinesterase (AChE), carboxylesterase (CaE), glutathione S-transferase (GST), and alkaline phosphatase (ALP) were evaluated at two different time points. An integrated biological response (IBRv2) index was elaborated with the biomarker results. The fungicide pulse had no impact on survival but temporarily reduced syrup consumption and increased the IBRv2 index, indicating potential molecular alterations. The neonicotinoid significantly reduced syrup consumption, survival, and the neurological activity of the enzymes. The co-exposure neonicotinoid-fungicide did not increase toxicity at the tested concentrations. AChE proved to be an efficient biomarker for the detection of early effects for both the insecticide and the fungicide. Our results highlight the importance of assessing individual and sub-individual endpoints to better understand pesticide effects on bees

Base de datos de abejas ibéricas

Las abejas son un grupo extremadamente diverso con más de 1000 especies descritas en la península ibérica. Además, son excelentes polinizadores y aportan numerosos servicios ecosistémicos fundamentales para la mayoría de ecosistemas terrestres. Debido a los diversos cambios ambientales inducidos por el ser humano, existen evidencias del declive de algunas de sus poblaciones para ciertas especies. Sin embargo, conocemos muy poco del estado de conservación de la mayoría de especies y de muchas de ellas ignoramos cuál es su distribución en la península ibérica. En este trabajo presentamos un esfuerzo colaborativo para crear una base de datos de ocurrencias de abejas que abarca la península ibérica e islas Baleares que permitirá resolver cuestiones como la distribución de las diferentes especies, preferencia de hábitat, fenología o tendencias históricas. En su versión actual, esta base de datos contiene un total de 87 684 registros de 923 especies recolectados entre 1830 y 2022, de los cuales un 87% presentan información georreferenciada. Para cada registro se incluye información relativa a la localidad de muestreo (89%), identificador y colector de la especie (64%), fecha de captura (54%) y planta donde se recolectó (20%). Creemos que esta base de datos es el punto de partida para conocer y conservar mejor la biodiversidad de abejas en la península ibérica e Islas Baleares. Se puede acceder a estos datos a través del siguiente enlace permanente: https://doi.org/10.5281/zenodo.6354502ABSTRACT: Bees are a diverse group with more than 1000 species known from the Iberian Peninsula. They have increasingly received special attention due to their important role as pollinators and providers of ecosystem services. In addition, various rapid human-induced environmental changes are leading to the decline of some of its populations. However, we know very little about the conservation status of most species and for many species, we hardly know their true distributions across the Iberian Peninsula. Here, we present a collaborative effort to collate and curate a database of Iberian bee occurrences to answer questions about their distribution, habitat preference, phenology, or historical trends. In total we have accumulated 87 684 records from the Iberian Peninsula and the Balearic Islands of 923 different species with 87% of georeferenced records collected between 1830 and 2022. In addition, each record has associated information such as the sampling location (89%), collector and person who identified the species (64%), date of the capture (54%) and plant species where the bees were captured (20%). We believe that this database is the starting point to better understand and conserve bee biodiversity in the Iberian Peninsula. It can be accessed at: https://doi.org/10.5281/zenodo.6354502Esta base de datos se ha realizado con la ayuda de los proyectos EUCLIPO (Fundação para a Ciência e a Tecnologia, LISBOA-01-0145-FEDER-028360/EUCLIPO) y SAFEGUARD (ref. 101003476 H2020 -SFS-2019-2).info:eu-repo/semantics/publishedVersio

Evaluation of Flowering Plant Strips and the Risk of Pesticides on Pollinators in Melon Agro-ecosystems

There is a growing concern worldwide about pollinator decline, because it threats both the maintenance of biodiversity conservation and the sustainable food production on a global scale. While it is universally agreed that the origin of pollinator loss is multifactorial, in intensive agricultural areas, the lack of flower resources and nesting opportunities, as well as the use of pesticides have been identified as one of the main causes. In this context, the goals of this thesis are to increase understanding of how changes in agricultural practices aiming at improving biodiversity could have an effect on pollinator-dependent crops, as well as to provide knowledge of the pesticide risk to pollinators in a realistic scenario. Planting flower strips adjacent to crops is among the habitat management practices employed to offer alternative floral resources to pollinators beyond the flowering of the crop itself. This measure seeks to improve pollinator population in agro-ecosystems and consequently pollination services. One of the greatest challenges of the design of flower-rich areas is the selection of the plants for the mix, with attractive potential for pollinator groups in the region and with hardly interspecific competition between them. In addition more information is needed to understand whether flower margins may play the double role of contributing to enhance the presence of pollinators in the crop environment and their potential spillover of pollinators on nearby pollinated dependent crops such as melon (Cucumis melo L.). Over the course of two consecutive years, the suitability of a flower mixture of 10 herbaceous plants for pollinators was evaluated on a weekly basis in a randomized block design of 2 melon plots with or without 1m-wide flower strips. We measured the floral coverage and pollinator visits to the plant species, as well as visits, yield, and quality of the crop. We identified four herbaceous plant species suitable to provide resources to pollinators and to be included in a flower strip in Central Spain based on their attractiveness, staggered blossom and coverage: Coriandrum sativum L., Diplotaxis virgata L., Borago officinalis L. and Calendula officinalis L. However, the plant composition must be carefully chosen, especially in the concurrence of blooming in the flower strip and melon crop. Flower strips can act either as pollinator competitor or facilitator to the crop depending on their floral coverage and/or the predominant species during the crop bloom period. We suggest that the concurrence of blooming of the rewarding plant C. officinalis with the melon crop should be avoided in our area, due to their attractive potential to the main pollinator taxa that visit the crop, thus preventing their displacement to the melon flowers. Moreover the selected mixture was tested during one year in a commercial melon field in order to know how far the flower strip could influence visitors in the crop. In the commercial plot, bee visitation rate in the melon flowers decreased with the distance to the flower strip. No influence due to the specifc flower strip evalueted on crop productivity or quality was found either in the experimental plots or in the commercial farm. Not only the agricultural intensification lower the availability of suitable habitats and food sources for pollinators, but agricultural habitats may also be further degraded due to the use of toxic pesticides to pollinators. Accordingly, for pesticides regulation, laboratory studies are required to assess the risk for pollinators, but nowadays the process presents some limitations. Traditionally, most laboratory studies on bee ecotoxicology test lethal and sublethal effects of single compounds following a short-term exposure. However, under field conditions, bees are often chronically exposed to a variety of chemicals, with potential synergistic effects. In addition, adult bees also can ingest important amounts of pollen. Therefore, to simulate pesticide oral exposure, the risk assessment should include exposure via pollen in combination with exposure via nectar. To overcome these limitations and to assess the impact of pesticides under a more realistic field scenario, first of all it is essential to know to which field concentrations pollinators are exposed. Secondly, we must know which are the most frequent pesticide combinations. In our work we have identified the pesticide residues found in pollen and nectar of commercial melon fields in Central Spain, and we have chosen the most probable combinations to perform chronic oral tests via pollen and nectar. Foraging bees in selected melon fields, had been exposed to a high number of pesticides (nine insecticides, nine fungicides and one herbicide). The highest pesticide residue concentrations (above 25 ppb) in melon flowers corresponded to pesticides sprayed by farmers. However, residues of eleven agrochemicals, not used by farmers during the current crop cycle were also detected in the samples showing that melon agro-ecosystem can be a pesticide contaminated environment. Pesticide concentrations in melon flowers were one or two orders of magnitude higher in pollen than in nectar. Three insecticides (acetamiprid, imidacloprid, chlorpyrifos) and one fungicide (myclobutanil) were detected in nectar. The most probable pesticide co-ocurrence (>60%) in the study area was between four insecticides (acetamiprid, oxamyl, imidacloprid and chlorpyrifos) and two fungicides (metalaxil-m and azoxystrobin). Based on these results, we selected one of the most frequent pesticide mixtures in our field–realistic scenario (acetamiprid, chlorphyrifos, oxamyl) to assess the impact on Bombus terrestris L. micro-colonies through a chronic oral toxicity test. We found neither an effect in the pollinator parameters measured (mortality, pollen and syrup collected and reproduction fitness), nor a synergy among compounds at concentration tested. Moreover, we studied the effects of three of the detected pesticides in the commercial melon fields (acetamiprid, imidacloprid and myclobutanil) on the solitary bee Osmia bicornis L. We orally exposed females of this species throughout their life span via pollen and sugar syrup. We measured pollen and syrup consumption, longevity, ovary maturation and thermogenesis. At the tested concentrations, no synergistic effects emerged, and we found no effects on longevity and ovary maturation. However, all treatments containing imidacloprid resulted in suppressed syrup consumption and drastic decreases in thoracic temperature and bee activity. Our results have important implications for pesticide regulation. If we had measured only lethal effects we would have wrongly concluded that the pesticide combinations containing imidacloprid were safe to O. bicornis. The incorporation of tests specifically intended to detect sublethal effects in bee risk assessment schemes should be an urgent priority. Moreover, pesticide intake was three orders of magnitude higher via syrup than pollen. It is reasonable to consider that the contamination via pollen may not have had a significantly influence on the results of the chronic oral toxicity tests with adults of this solitary bee at field realistic concentration. In addition, we have used bumblebee (B. terrestris) micro-colonies in order to evaluate the influence of imidacloprid exposure at field-realistic concentrations through the double route of contamination (nectar and pollen), and to assess whether contamination via pollen shows the same results as those found with O. bicornis adults. The micro-colony studies allowed us to measure effects on adults, on brood development and on offspring (males). Pollen is the essential protein source to larvae. Therefore we hypothesized that the double route of contamination could have an influence on the development of the micro-colony, especially on the brood production and male progeny. We found no effects on workers survival. However micro-colonies exposed to imidacloprid collected less syrup and pollen, produced less brood, and consequently less males were emerged. In agreement with the O. bicornis study, these effects mainly come from contaminated nectar treatments, because no differences were found between micro-colonies exposed to imidacloprid via nectar and pollen (N+P), and those exposed just via nectar (N), neither between the control and the micro-colonies exposed to imidicloprid via pollen (P). ----------RESUMEN---------- Existe una creciente preocupación en todo el mundo sobre el declive de los polinizadores, siendo una amenaza tanto para el mantenimiento y la conservación de la biodiversidad como la producción de alimentos a escala mundial. Si bien el origen de las pérdidas de polinizadores está universalmente aceptado que es multifactorial, en áreas de agricultura intensiva, la falta de recursos florales y oportunidades de anidación, así como el uso de pesticidas, se han identificado como una de las principales causas. En este contexto, los objetivos de esta tesis se centran en aumentar el conocimiento de cómo los cambios en las prácticas agrícolas destinadas a mejorar la biodiversidad podrían tener un efecto en los cultivos que dependen de los polinizadores, así como evaluar el riesgo de pesticidas sobre estos insectos beneficioso en un escenario realista. La implementación de márgenes florales adyacentes a los cultivos es una de las prácticas de manejo del hábitat que se está fomentando para ofrecer fuentes alternativas de polen y néctar a los polinizadores más allá de la floración del propio cultivo. Esta medida busca mejorar las poblaciones de polinizadores en agro-ecosistemas y, en consecuencia, los servicios de la polinización. Uno de los mayores desafíos en el diseño de estas áreas ricas en flores es la selección de las plantas que formarán parte de la mezcla floral. Estas especies deberán contar con un adecuado potencial atractivo para los grupos de polinizadores de la zona y con una baja competencia interespecífica entre ellas. Además, es necesaria más información para comprender si los márgenes florales pueden desempeñar el doble papel de contribuir a mejorar la presencia de polinizadores en el entorno agrario y su potencial para desplazar los polinizadores hacia los cultivos cercanos con polinización entomófila como el melón (Cucumis melo L.). Durante dos años consecutivos, se evaluó la idoneidad de una mezcla de flores de 10 plantas herbáceas para polinizadores en un diseño de bloques al azar con 2 parcelas de melón con o sin márgenes florales de 1 m de ancho. Medimos la cobertura floral y las visitas de polinizadores en las diferentes especies de plantas, así como las visitas, el rendimiento y la calidad en el cultivo. Identificamos cuatro especies de plantas herbáceas adecuadas para proporcionar recursos a los polinizadores, y con potencial para ser incluidas en márgenes florales en el centro de España, en función de su poder atractivo, floración escalonada y cobertura floral: Coriandrum sativum L., Diplotaxis virgata L., Borago officinalis L. y Calendula officinalis L. Sin embargo, la composición de las plantas debe elegirse cuidadosamente, especialmente cuando la floración de los márgenes florales y el cultivo de melón coinciden. Los márgenes florales pueden actuar como competidores o como facilitadores de polinizadores al cultivo, dependiendo de su cobertura floral y/o de las especies predominantes durante el período de floración del melón. En base a nuestros resultados, se recomienda evitar la concurrencia de la floración de C. officinalis, planta que ofrece gran cantidad de polen y néctar, con el cultivo de melón en nuestra área. Su potencial atractivo para los principales taxones de polinizadores que visitan el cultivo podría evitar su desplazamiento hacia las flores de melón. Además, la mezcla seleccionada se probó durante un año en una finca comercial de melón con el objetivo de conocer el alcance de influencia del margen floral en las visitas en el cultivo. En la parcela comercial, la tasa de visitas de polinizadores en las flores de melón disminuyó con la distancia al margen floral. No se encontró ninguna influencia de los márgenes florales en la productividad o calidad del cultivo, ni en las parcelas experimentales ni en la finca comercial. No sólo la intensificación agrícola reduce la disponibilidad de hábitats y fuentes de alimentos adecuados para los polinizadores, sino que los hábitats agrícolas también pueden degradarse aún más debido al uso de pesticidas tóxicos para los polinizadores. En consecuencia, para la regulación de pesticidas, se requieren estudios de laboratorio que evalúen su riesgo en los polinizadores, pero hoy en día el proceso presenta algunas limitaciones. Tradicionalmente, la mayoría de los estudios de laboratorio sobre ecotoxicología de abejas prueban los efectos letales y subletales de compuestos individuales después de una exposición a corto plazo. Sin embargo, en condiciones de campo, las abejas a menudo están crónicamente expuestas a una variedad de productos químicos, con posibles efectos sinérgicos. Además, las abejas adultas, también pueden ingerir cantidades importantes de polen. Por lo tanto, para simular la exposición oral de pesticidas, en las evaluaciones del riesgo se debería incluir la exposición a través del polen en combinación con la exposición a través del néctar. Para superar estas limitaciones y evaluar el impacto de los pesticidas en un escenario de campo más realista, en primer lugar es esencial saber a qué concentraciones de campo están expuestos los polinizadores. En segundo lugar, debemos conocer cuáles son las combinaciones de pesticidas más frecuentes. En nuestro trabajo hemos identificado los residuos de pesticidas encontrados en el polen y el néctar de campos comerciales de melón en el centro de España. Hemos elegido las combinaciones más probables para realizar pruebas de exposición crónicas vía oral (polen y néctar). Las abejas que se alimentaron en los campos seleccionados de melón estuvieron expuestas a una gran cantidad de pesticidas (nueve insecticidas, nueve fungicidas y un herbicida). Las concentraciones más altas de residuos de pesticidas (superiores a 25 ppb) en las flores de melón eran de pesticidas aplicados por los agricultores. Sin embargo, en las muestras también se detectaron residuos de once agroquímicos no utilizados durante el ciclo de cultivo, lo que revela que el agro-ecosistema de melón puede ser un ambiente contaminado con pesticidas. Las concentraciones de pesticidas en las flores de melón fueron uno o dos órdenes de magnitud más altas en polen que en néctar. Se detectaron tres insecticidas (acetamiprid, imidacloprid, clorpirifos) y un fungicida (miclobutanil) en el néctar. La concurrencia más probable de pesticidas (>60%) en el área de estudio fue entre cuatro insecticidas (acetamiprid, oxamil, imidacloprid y clorpirifos) y dos fungicidas (metalaxil-m y azoxistrobina). Basándonos en estos resultados, seleccionamos una de las mezclas de pesticidas más frecuentes en nuestro escenario realista (acetamiprid, clorpirifos, oxamil) para evaluar el impacto en las micro-colmenas de Bombus terrestris L. a través de una prueba de toxicidad oral crónica. No encontramos ningún efecto en los parámetros medidos (mortalidad, polen y néctar recolectado y capacidad reproductiva), ni tampoco efectos sinérgicos entre los compuestos. Además, estudiamos los efectos de tres de los plaquicidas detectados en los campos comerciales de melón (acetamiprid, imidacloprid y miclobutanil) en la abeja solitaria Osmia bicornis L. Las hembras fueron expuestas oralmente a los agroquímicos a lo largo de su vida a través del polen y del néctar. Medimos el consumo de polen y néctar, la longevidad, la maduración de los ovarios y la termogénesis. A las concentraciones probadas, no surgieron efectos sinérgicos, y no encontramos efectos sobre la longevidad y la maduración de los ovarios. Sin embargo, en todos los tratamientos que contenían imidacloprid se redujo el consumo néctar y hubo una disminución drástica de la temperatura torácica y la actividad de las abejas. Nuestros resultados tienen implicaciones importantes para la regulación de pesticidas. Si hubiéramos medido sólo los efectos letales, habríamos concluido erróneamente que las combinaciones de pesticidas que contenían imidacloprid eran seguras para O. bicornis. La incorporación de pruebas específicamente destinadas a detectar efectos subletales en los esquemas de evaluación de riesgo de abejas debería ser una prioridad urgente. Además, la ingesta de pesticidas fue tres órdenes de magnitud mayor a través del sirope que del polen. Es razonable considerar que la contaminación vía polen puede no tener una gran influencia en los resultados de las pruebas de toxicidad oral crónica con adultos de esta abeja solitaria a concentraciones realistas. Asimismo, hemos utilizado micro-colmenas de B. terrestris con el objetivo de evaluar la influencia de la exposición a concentraciones realistas de campo de imidacloprid a través de la doble ruta de contaminación (néctar y polen) y evaluar si la contaminación a través del polen revelaba los mismos resultados que aquellos encontrados con adultos de O. bicornis. Los ensayos con micro colmenas permiten medir los tanto efectos en adultos como en el desarrollo de la cría y en la descendencia (machos). El polen es la fuente esencial de proteínas para las larvas. Por lo tanto, planteamos la hipótesis de que la doble ruta de contaminación podría influir mayoritariamente en el desarrollo de la micro colmena, especialmente en la producción de cría y la progenie masculina. No encontramos efectos sobre la supervivencia de los adultos. Sin embargo, las micro-colmenas expuestas al imidacloprid recolectaron menos néctar y polen, produjeron menos cría y, en consecuencia, la emergencia de los machos fue menor. Tal y como se observó en los ensayos con O. bicornis, el efecto procedió principalmente de los tratamientos de néctar contaminado, porque no se encontraron diferencias entre las micro-colmenas expuestas al imidacloprid a través del néctar y el polen (N+P) y aquellas expuestas solo a través del néctar (N); tampoco entre el control y las micro-colmenas expuestas al imidicloprid vía polen (P)

Effects of chronic exposure to the new insecticide sulfoxaflor in combination with a SDHI fungicide in a solitary bee

The recent EU ban of the three most widely used neonicotinoids (imidacloprid, thiamethoxam and clothianidin) to all outdoors applications has stimulated the introduction of new insecticides into the market. Sulfoxaflor is a new systemic insecticide that, like neonicotinoids, acts as a modulator of nicotinic acetylcholine receptors. In agro-environments, bees can be exposed to this compound via contaminated pollen and nectar for long periods of time. Therefore, it is important to assess the potential effects of chronic exposure to sulfoxaflor, alone and in combination with fungicides, on pollinators. In this study, we tested the effects of chronic exposure to two field concentrations of sulfoxaflor (20 and 100 ppb) alone and in combination with four concentrations of the fungicide fluxapyroxad (7500, 15,000, 30,000 and 60,000 ppb) on syrup consumption and longevity in females of the solitary bee Osmia bicornis L. Exposure to 20 ppb of sulfoxaflor, alone and in combination with the fungicide, stimulated syrup consumption, but did not affect longevity. In contrast, syrup consumption decreased in bees exposed to 100 ppb, all of which died after 2–6 days of exposure. We found no evidence of synergism between the two compounds at any of the two sulfoxaflor concentrations tested. Comparison of our findings with the literature, confirms that O. bicornis is more sensitive to sulfoxaflor than honey bees. Our results highlight the need to include different bee species in risk assessment schemes.This study was supported by a grant from the University of Bologna to FS (Grant RFO2019_SGOLASTRA), the Spanish Ministry of Science, Innovation and Universities (Grant R+D RTI2018-098399-B-I00) and the postdoctoral fellowship from the French Association POLLINIS (www.pollinis.org) to CA

Chronic oral exposure to field-realistic pesticide combinations via pollen and nectar : effects on feeding and thermal performance in a solitary bee

Pesticide use is one of the main causes of pollinator declines in agricultural ecosystems. Traditionally, most laboratory studies on bee ecotoxicology test acute exposure to single compounds. However, under field conditions, bees are often chronically exposed to a variety of chemicals, with potential synergistic effects. We studied the effects of field-realistic concentrations of three pesticides measured in pollen and nectar of commercial melon fields on the solitary bee Osmia bicornis L. We orally exposed females of this species throughout their life span to 8 treatments combining two neonicotinoid insecticides (acetamiprid, imidacloprid) and a triazole fungicide (myclobutanil) via pollen and sugar syrup. We measured pollen and syrup consumption, longevity, ovary maturation and thermogenesis. Pesticide intake was three orders of magnitude higher via syrup than pollen. At the tested concentrations, no synergistic effects emerged, and we found no effects on longevity and ovary maturation. However, all treatments containing imidacloprid resulted in suppressed syrup consumption and drastic decreases in thoracic temperature and bee activity. Our results have important implications for pesticide regulation. If we had measured only lethal effects we would have wrongly concluded that the pesticide combinations containing imidacloprid were safe to O. bicornis. The incorporation of tests specifically intended to detect sublethal effects in bee risk assessment schemes should be an urgent priority. In this way, the effects of pesticide exposure on the dynamics of bee populations in agroecosystems will be better assessed

The Role of Annual Flowering Plant Strips on a Melon Crop in Central Spain. Influence on Pollinators and Crop

Planting flower strips adjacent to crops is among the habitat-management practices employed to offer alternative floral resources to pollinators. However, more information is needed to understand their potential spill-over of pollinators on nearby insect-pollinated crops. Over the course of two consecutive years, the suitability of a flower mixture of 10 herbaceous plants for pollinators was evaluated on a weekly basis, in a randomized block design of two melon plots (10 × 10 m2) with or without 1 m-wide flower strips. Floral coverage and pollinator visits to the plant species, as well as pollinator visits and the yield and quality of the crop, were assessed. Additionally, the selected mixture was tested for 1 year in a commercial field in order to ascertain how far the flower strip could influence visitors in the crop. The most suitable species for a flower strip in central Spain based on their attractiveness, floral coverage and staggered blossom were Coriandrum sativum L., Diplotaxis virgata L., Borago officinalis L. and Calendula officinalis L. The flower strip can act as either pollinator competitor or facilitator to the crop, depending on their floral coverage and/or the predominant species during the crop bloom period. The concurrence of blooming of the rewarding plant C. officinalis with the melon crop should be avoided in our area. In the commercial field, the bee visitation rate in the melon flowers decreased with the distance to the flower strip. No influence of the specific flower strip evaluated on crop productivity or quality was found