A reciprocal transplant experiment confirmed mite-resistance in a honey bee population from Uruguay

In the past few years there has been an increasing interest for the study of honey bee populations that are naturally resistant to the ectoparasitic mite Varroa destructor, aiming to identify the mechanisms that allow the bees to limit the reproduction of the mite. In eastern Uruguay there are still bees resistant to mites that survive without acaricides. In order to determine if the differential resistance to V. destructor was maintained in other environments, a reciprocal transplant experiment was performed between the mite-resistant bee colonies and the mite-susceptible bee colonies from the east and the west of the country, respectively, infesting bees with local mites. In both regions, the mite-resistant colonies expressed a higher hygienic behavior and presented a higher phoretic mites/reproductive mites and mites in drone cells/mites in worker cells ratio than the mite-susceptible colonies. All the mite-susceptible colonies died during fall–winter, while a considerable number of mite-resistant colonies survived until spring, especially in the east of the country. This study shows that the bees in the east of the country maintain in good measure the resistance to V. destructor in other regions and leaves open the possibility that the mites of the two populations have biases in the reproductive behavior.INIA: PF10.ANII:POS_NAC_2013_1_1225

Unraveling honey bee–varroa destructor interaction: multiple factors involved in differential resistance between two uruguayan populations

The ectoparasite Varroa destructor is the greatest biotic threat of honey bees Apis mellifera in vast regions of the world. Recently, the study of natural mite-resistant populations has gained much interest to understand the action of natural selection on the mechanisms that limit the mite population. In this study, the components of the A. mellifera–V. destructor relationship were thoroughly examined and compared in resistant and susceptible honey bee populations from two regions of Uruguay. Mite-resistant honey bees have greater behavioral resistance (hygienic and grooming behaviors) than susceptible honey bees. At the end of the summer, resistant honey bees had fewer mites and a lower deformed wing virus (DWV) viral load than susceptible honey bees. DWV variant A was the only detected variant in honey bees and mites. Molecular analysis by Short Tandem Repeat showed that resistant honey bees were Africanized (A. m. scutellata hybrids), whereas susceptible honey bees were closer to European subspecies. Furthermore, significant genetic differentiation was also found between the mite populations. The obtained results show that the natural resistance of honey bees to V. destructor in Uruguay depends on several factors and that the genetic variants of both organisms can play a relevant rol

Epormenis cestri secretions in Sebastiania schottiana trees cause mass death of honey bee Apis mellifera larvae in Uruguay

For more than 60 years, sporadic cases of massive summer honey bee larvae mortality in colonies located near freshwater systems with abundant riparian vegetation have been reported in Uruguay. This odd phenomenon, known as “River disease” by beekeepers, can lead to colony death by depopulation. The aim of this study was to detect the causes of larvae death. Different experiments and analyses were performed using affected apiaries located between two important water courses. 1 day old larvae were the most susceptible and substances that killed the larvae were present in the nectar but not in the pollen. A palynological analysis of nectar samples showed that bees collect this resource from commonly pollinated floral species in the country. However, abundant fungi spores and conidia were found, which indicates that the bees also collected honeydews. In the riparian vegetation, bees were observed collecting the secretions of the planthopper Epormenis cestri on Sebastiania schottiana trees. It was found that the mortality period of larvae overlaps with the presence of E. cestri. Larvae maintained in the laboratory were fed (i) nectar from healthy colonies, (ii) nectar from affected colonies, and (iii) secretions of E. cestri. The mortality of the larvae that received nectar from colonies affected with River disease and secretions of E. cestri was higher than the mortality of those receiving nectar from healthy colonies. This represents the first report of planthopper honeydew causing mass larval mortality in honey bees

Dependência da polinização animal em goiaba [Acca sellowiana (Berg) Burret] (Myrtaceae) e variação de polinizadores entre regiões do Uruguai

The Feijoa “Guayabo del país” (Acca sellowiana) is a native Myrtaceae whose fruits have a great commercial potential for their nutritive properties. The objectives of this study were to determine the extent to which fruit production depends on biotic pollination and to identify potential pollinators in Uruguay. Two farms and three park, located in Salto and Canelones were used for the study. The percentage of fruit set in the branches excluding pollinators did not exceed 5.1%, whereas in the branches with free access of pollinators it varied between 10.4% (Salto) and 90.9% (park trees, Canelones). A total of 28 insect species and 3 Passeriforme species were identified on the flower varying with the region. Apis mellifera were present on all plantations with high frequency. Remarkably, 7 species of native bees and 3 species of native passerines were found only in the southern trees of the country. Some pollinators can be managed to improve production, of commercial quality, like honeybees or bumblebees.A goiaba “Guayabo del país” (Acca sellowiana) é uma Myrtaceae nativa cujos frutos apresentam grande potencial comercial por suas propriedades nutritivas. Os objetivos deste estudo foram determinar em que medida a produção de frutos depende da polinização biótica e identificar potenciais polinizadores no Uruguai. Duas fazendas e três parques, localizados em Salto e Canelones, foram utilizados para o estudo. A porcentagem de frutificação nos ramos excluindo polinizadores não ultrapassou 5,1%, enquanto nos ramos com livre acesso de polinizadores variou entre 10,4% (Salto) e 90,9% (árvores do parque, Canelones). Um total de 28 espécies de insetos e 3 espécies de Passeriformes foram identificados na flor variando com a região. Apis mellifera esteve presente em todos os plantios com alta frequência. Notavelmente, 7 espécies de abelhas nativas e 3 espécies de passeriformes nativos foram encontrados apenas nas árvores do sul do país. Alguns polinizadores podem ser manejados para melhorar a produção, de qualidade comercial, como abelhas ou zangões

Animal pollination dependence in Feijoa [Acca sellowiana (Berg) Burret] (Myrtaceae) and variation of pollinators between regions of Uruguay: Dependência da polinização animal em goiaba [Acca sellowiana (Berg) Burret] (Myrtaceae) e variação de polinizadores entre regiões do Uruguai

The Feijoa “Guayabo del país” (Acca sellowiana) is a native Myrtaceae whose fruits have a great commercial potential for their nutritive properties. The objectives of this study were to determine the extent to which fruit production depends on biotic pollination and to identify potential pollinators in Uruguay. Two farms and three park, located in Salto and Canelones were used for the study. The percentage of fruit set in the branches excluding pollinators did not exceed 5.1%, whereas in the branches with free access of pollinators it varied between 10.4% (Salto) and 90.9% (park trees, Canelones). A total of 28 insect species and 3 Passeriforme species were identified on the flower varying with the region. Apis mellifera were present on all plantations with high frequency. Remarkably, 7 species of native bees and 3 species of native passerines were found only in the southern trees of the country. Some pollinators can be managed to improve production, of commercial quality, like honeybees or bumblebees

Impact of nutritional stress on the honeybee colony health

Honeybees Apis mellifera are important pollinators of wild plants and commercial crops. For more than a decade, high percentages of honeybee colony losses have been reported worldwide. Nutritional stress due to habitat depletion, infection by different pests and pathogens and pesticide exposure has been proposed as the major causes. In this study we analyzed how nutritional stress affects colony strength and health. Two groups of colonies were set in a Eucalyptus grandis plantation at the beginning of the flowering period (autumn), replicating a natural scenario with a nutritionally poor food source. While both groups of colonies had access to the pollen available in this plantation, one was supplemented with a polyfloral pollen patty during the entire flowering period. In the short-term, colonies under nutritional stress (which consumed mainly E. grandis pollen) showed higher infection level with Nosema spp. and lower brood and adult bee population, compared to supplemented colonies. On the other hand, these supplemented colonies showed higher infection level with RNA viruses although infection levels were low compared to countries were viral infections have negative impacts. Nutritional stress also had long-term colony effects, because bee population did not recover in spring, as in supplemented colonies did. In conclusion, nutritional stress and Nosema spp. infection had a severe impact on colony strength with consequences in both short and long-term

Sanitary situation of honey bees in Uruguay: novelties of the last decade

En los últimos años, la apicultura en Uruguay se enfrenta con bajos rendimientos de producción de miel y pérdidas anuales de colonias que pueden alcanzar el 30%, estando los problemas sanitarios involucrados en buena parte de esta situación. A nivel mundial la investigación sobre los factores que amenazan a las poblaciones de abejas melíferas se ha ampliado, abarcando los problemas nutricionales, la respuesta inmune, la microbiota intestinal, la identificación de nuevos patógenos o variantes de los mismos, el efecto de los agroquímicos, y otros insectos que comparten patógenos con las abejas melíferas. Respecto a la varroosis la investigación se ha enfocado en las poblaciones de abejas sobrevivientes a Varroa destructor. En Uruguay, la investigación sobre salud de las abejas melíferas en los últimos 10 años ha sido muy prolífica abordando buena parte de los temas mencionados desde las condiciones particulares que presenta el país. Esta revisión sobre la situación sanitaria de las abejas melíferas en Uruguay se centra en resultados de investigaciones nacionales sobre las parasitosis y virosis más prevalentes, la identificación de un nuevo parásito, el efecto de la nutrición y el herbicida glifosato tanto en la microbiota intestinal como en la sanidad, el estudio de parásitos y virus de las abejas melíferas presentes en abejorros nativos del género Bombus, y la descripción de una enfermedad específica del país como es el Mal del Río. Se resalta la importancia de los diferentes resultados para la apicultura nacional y se ponen en contexto con la información internacional reciente.In recent years, beekeeping industry in Uruguay faces low honey production yields and annual colony losses that can reach 30%, and health problems are involved in much of this situation. Worldwide, research on the factors that threaten honey bee populations has expanded, encompassing nutritional problems, the immune response, the intestinal microbiota, identification of new pathogens or its variants, the effect of agrochemicals, and other insects that share pathogens with honey bees. Regarding varroosis, research has focused on the populations of bees surviving Varroa destructor. In Uruguay, research on the health of honey bees in the last 10 years has been very prolific, addressing a good part of the aforementioned issues taking into account the particular conditions that the country presents. This review on the health situation of honey bees in Uruguay focuses on the results of national research on the most prevalent parasitosis and virosis, the identification of a new parasite, the effect of nutrition and the herbicide glyphosate on the intestinal microbiota and on the health, the study of parasites and viruses of honey bees present in native bumblebees of the genus Bombus, and the description of the country-specific disease (River disease). The importance of the diverse results for national beekeeping is highlighted and put in context with recent international information

ACUTE CONTACT TOXICITY TEST OF OXALIC ACID ON HONEYBEES IN THE SOUTHWESTERN ZONE OF URUGUAY

This work studies the acute contact toxicity of oxalic acid (OA) on a honeybee polyhybrid subspecies ( Apis mellifera ), which is the dominant biotype in southwestern zone of Uruguay (SWZU) and the country’s most important honey-producing region. We determined the mean lethal dose (LD50), as well as the no observed effect level (NOEL) and the lowest observed effect level (LOEL) values. We also estimated the total number of honeybees per hive in the test area. The aim was to assess the relationship between the maximum OA dose used in Uruguay (3.1 g OA per hive) and the toxicological parameters of honeybees from SWZU. The current dose of 3.1 g OA per hive corresponds to 132.8 μg OA per honeybee since determined NOEL is 400 μg OA per honeybee; our results indicate that the current dose could be increased to 9.3 g OA per hive. The results also highlight some differences between the LD50 value in SWZU honeybees (548.95 μg OA per honeybee) and some published LD50 values for other honeybee subspecies

Selección bidireccional de Apis mellifera (Hymenoptera: Apidae) para aumento de la resistencia y la susceptibilidad a la nosemosis

La nosemosis es una enfermedad que afecta las funciones digestivas de las abejas melíferas causada por los microsporidios Nosema apis y Nosema ceranae. En Uruguay la única especie detectada es N. ceranae. Para determinar si la incidencia de N. ceranae en las colonias tiene un componente genético se realizó una selección bidireccional para aumento de la resistencia y la susceptibilidad a este parásito sin control de la paternidad. Las colonias fueron evaluadas en una forestación de Eucalyptus grandis en otoño. La infección de las colonias se determinó como 1) el porcentaje de abejas pecoreadoras infectadas y 2) el número promedio de esporas por campo en 10 campos. El trabajo se inició con 138 colonias y se evaluaron dos generaciones de 30 y 63 colonias. La respuesta a la selección fue muy limitada, solo en la primera generación las colonias de la línea resistente presentaron menos esporas por abejas que las colonias de la línea susceptible (19,6 ± 5,8 y 26,8 ± 10,4, respectivamente, W = 41,5; P = 0.03). Esto indicaría que la resistencia a la nosemosis está fuertemente afectada por el ambiente. Futuros esfuerzos para aumentar la resistencia de las abejas a N. ceranae a través de mejora genética deberán incluir el control de la paternidad

Nosema ceranae and RNA viruses in European and Africanized honeybee colonies (Apis mellifera) in Uruguay

International audienceNosema ceranae is one of the causative agents of Nosemosis, a severe disease that affects the honeybee Apis mellifera. The aim of the present work was to compare N. ceranae and RNA virus infections in Africanized bees (hybrid of Apis mellifera scutellata and A. m. mellifera) and European (Italian) bees (A. m. ligustica) under field conditions. Africanized and Italian healthy colonies were relocated to an Eucalyptus grandis plantation, a place where colonies inevitably acquire Nosemosis. Fifteen and 30 days after that, all colonies presented N. ceranae spores although Africanized bees were less infected than Italian bees. Sacbrood virus (SBV) and Black queen cell virus (BQCV) were detected in both races of bees, although Africanized bees presented a lower level of BQCV infection than Italian bees. At the end of the flowering period, Africanized colonies had a larger honeybee population and produced more honey than Italian colonies. These results suggest that Africanized bees may be able to limit N. ceranae and BQCV infections within the colony, and that this may allow them to be more productive