Reproduction of Varroa destructor in sealed worker bee brood cells of Apis mellifera carnica and Apis mellifera syriaca in Jordan

The reproduction of the honey bee mite, Varroa destructor in sealed worker bee brood cells represents an important factor for the population development of this parasite in honey bee colonies. In this study, the relative infestation levels of worker brood cells, mite fertility (mites that lay at least one egg) and reproductive rate (number of viable adult daughters per mother mite) of Varroa mite in worker brood cells of Apis m. carnica and Apis m. syriaca were compared in fall 2003 and summer 2004 at two locations in Jordan. The relative infestation levels in sealed worker brood cells ranged from 23 – 32 % in fall and 19 – 28 % in summer. The average fertility of Varroa mite ranged between 90 - 98% in colonies of A. m. carnica and between 88 - 96 % in A. m. syriaca with minor differences between colonies and locations. The number of total progeny of fertile mites in worker brood cells was 4.0 in both bee races. The reproductive rate was high with 2.7 and 2.6 in both honey bee races. The post-capping period of the worker brood cells differs only slightly between both bee races and between locations (284.4 h on average, n = 4,000). Our data reveal surprisingly high mite fertility and reproductive rates in both honeybee races under Mediterranean conditions of Jordan. The possible physiological background of Varroa reproduction and the impact of mite fertility on the development of Varroa tolerance are discussed

Infestation levels of Varroa destructor in local honey bees of Jordan

To determine Varroa mite infestation levels in Jordan, a survey covering 180 colonies of two bee types (Apis m. syriaca and Apis m. syriaca hybrids) from six locations of 4 climatic zones was conducted during August, 8 month after the last treatment. Sampled colonies had 8-10 frames covered with bees and 3-4 brood frames. Levels of infestation were determined on both adult worker bees and in sealed worker brood cells. Two-way ANOVA showed no significant differences due to bee type with average adult bee infestation of 10.9 % and 13.1 % on hybrid and local bee types, respectively. Average infestation levels in sealed brood worker cells were 37.6 % and 32.5 % in hybrid and local bee types, respectively. Differences in infestation levels on adult bees were significant due to location and ranged between 6.9 - 18.6 % in Daba’a (Desert climate) and Jerash (Dry Mediterranean), respectively. In sealed worker brood cells infestation levels ranged between 15.7 - 84.7 % in Baqa (Dry Mediterranean) and Jerash, respectively. This indicates clearly that the usual scheduled Varroa control practice by a single chemical treatment in autumn could be insufficient. Therefore, to prevent damages or even losses of colonies, including diagnosis of infestation rates as part of integrated Varroa management is highly recommended

Periodical honey bee colony losses in Germany: preliminary results from a four years monitoring project

contribution to session V Honey bee poisoning incidents and monitoring schemesWithin the framework of the German Bee Monitoring Project winter losses of bee colonies were evaluated from the database of 120 beekeepers and 1200 bee colonies by assessing the following parameters: data on the apiary (site, nuclei, movement of colonies, Varroa treatment), strength of the colonies in autumn and spring, honey yields, residues in bee bread (stored pollen), bee disease analysis.During the last four years the winter losses of the monitoring beekeepers were between 8 and 16% and showed regional differences. The loss rates were clearly lower than those of non-monitoring beekeepers.In 215 bee bread samples analysed with a sensitive multi-method, more than 55 active ingredients were found. Most active ingredients were found in traces but often in combinations. Primarily fungicides, varroacides and herbicides were found. Clothianidin was not found in any sample. Imidacloprid was found in one sample at the limit of detection. 4400 data sets were statistically analysed for the identification of triggers with negative influence on overwintering. The winter losses were significantly correlated with Varroa infestations and virus infections in autumn. It was concluded that no acute effects on honey bees have to be expected on the basis of the evaluated residue data. For testing potential sublethal or long term effects a useful test design has to be developed. The project will be continued in 2009.Keywords: German Bee Monitoring Project, colony losses, Apis mellifera, overwinterin

The limits of internal devaluation: Switzerland during the Great Depression

During the Great Depression, countries endowed with abundant gold reserves were not able to leave the gold standard and devalue their currencies until the mid-1930s. Instead, they were forced to go down the road of internal devaluation. We analyze the policies of the Swiss authorities by estimating a New Keynesian small open economy model. Our results show that the long adherence to the gold standard and the failure of internal devaluation imposed considerable costs on the Swiss economy. Moreover, counterfactual exercises suggest that a timely devaluation would have led to an early recovery from the Great Depression

Defined exposure of honey bee colonies to simulated radiofrequency electromagnetic fields (RF-EMF): Negative effects on the homing ability, but not on brood development or longevity

Urbanization and the increasing use of wireless technologies lead to higher emission rates of radiofrequency electromagnetic fields (RF-EMF) in populated areas. This anthropogenic electromagnetic radiation is a form of environmental pollution and a potential stressor on bees or other flying insects. Cities often have a high density of wireless devices operating on microwave frequencies, which generate electromagnetic frequencies e.g. in the 2.4 and 5.8 GHz bands commonly used by the wireless technologies. To date the effects of nonionizing electromagnetic radiation on the vitality and behavior of insects are poorly understood. In our experiment we used honey bees as model organisms and analyzed the effects of defined exposures to 2.4 and 5.8 GHz on brood development, longevity and homing ability under field conditions. To generate this radiation, we used a high-quality radiation source which generates a consistent, definable and realistic electromagnetic radiation, engineered for this experiment by the Communications Engineering Lab (CEL) at the Karlsruhe Institute of Technology. Our results show significant effects of long-term exposures on the homing ability of foraging honey bees, but no effects on brood development and adult worker longevity. Using this novel and high-quality technical set-up, this interdisciplinary work provides new data on the effects of these widely used frequencies on important fitness parameters of free-flying honey bees

Business cycles in emerging markets: the role of liability dollarization and valuation effects

Understanding differences in business cycle phenomena between Emerging Market Economies (EMEs) and industrialized countries has been at the center of recent research on macroeconomic fluctuations. The purpose of this paper is to investigate the importance of certain credit market imperfections in different EMEs. To this end, we develop a small open economy Dynamic Stochastic General Equilibrium (DSGE) framework featuring both permanent and transitory productivity shocks, differentiated home and foreign goods, and endogenous exchange rate movements. Furthermore, our model incorporates liability dollarization as a particular form of financial frictions in EMEs. In this vein, we account for the fact that emerging markets traditionally have had difficulties in borrowing in domestic currency on international capital markets and thus allow for valuation effects in our analysis. We estimate our model using Bayesian techniques for a number of EMEs and thereby control for potential heterogeneity across countries. Contrary to previous studies in this strand of the literature, we include a (vector-)autoregressive measurement error component to capture off-model dynamics. Regarding business cycles in emerging markets, our main findings are that (i) even though we incorporate financial frictions in the framework, trend shocks are the main determinant of macroeconomic fluctuations, (ii) accounting for liability dollarization ameliorates the model fit, and (iii) valuation effects on average stabilize changes in the net foreign asset position

Alumni Profiles

Six former students with close remaining ties to UZH have provided short profiles of their experience at UZH and in their later careers. Since their time at UZH, they have become professors, founders of companies, heads of industrial research in leading chemical companies, patent attorneys, among other careers. They clearly illustrate how personally beneficial a UZH training can be

The virulent, emerging genotype B of Deformed wing virus is closely linked to overwinter honeybee worker loss

Bees are considered to be threatened globally, with severe overwinter losses of the most important commercial pollinator, the Western honeybee, a major concern in the Northern Hemisphere. Emerging infectious diseases have risen to prominence due to their temporal correlation with colony losses. Among these is Deformed wing virus (DWV), which has been frequently linked to colony mortality. We now provide evidence of a strong statistical association between overwintering colony decline in the field and the presence of DWV genotype-B (DWV-B), a genetic variant of DWV that has recently been shown to be more virulent than the original DWV genotype-A. We link the prevalence of DWV-B directly to a quantitative measure of overwinter decline (workforce mortality) of honeybee colonies in the field. We demonstrate that increased prevalence of virus infection in individual bees is associated with higher overwinter mortality. We also observed a substantial reduction of infected colonies in the spring, suggesting that virus-infected individuals had died during the winter. Our findings demonstrate that DWV-B, plus possible A/B recombinants exhibiting DWV-B at PCR primer binding sites, may be a major cause of elevated overwinter honeybee loss. Its potential emergence in naïve populations of bees may have far-reaching ecological and economic impacts

Reproductive parameters of female Varroa destructor and the impact of mating in worker brood of Apis mellifera

During a reproductive cycle, not all daughter mites of Varroa destructor mate and thus leave the brood cells as virgins. Here, we show that virgin mites are present within both the phoretic (10%) and reproductive (8%) mite population. Most (n = 29 of n = 33) of these encountered virgins laid unfertilized (= male) eggs, and some (n = 10) mated later on with their own son. These findings were verified by tests with artificially reared virgin mites. Obviously, mating is not a prerequisite for Varroa reproduction. However, due to the small number of reproductive cycles, the contribution of virgins to the Varroa population is regarded as low. This study also confirms conclusively that sex of V. destructor is determined via arrhenotokous parthenogenesis and not—as previously assumed—via pseudo-arrhenotoky. Furthermore, reproductive parameters of naturally invaded and artificially introduced Varroa females were compared, and artificial infestation was reconfirmed as a suitable method.Fil: Häußermann, Claudia Katharina. Universidad de Hohenheim; AlemaniaFil: Giacobino, Agostina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Munz, Rosalie. Universidad de Hohenheim; AlemaniaFil: Ziegelmann, Bettina. Universidad de Hohenheim; AlemaniaFil: Palacio, Maria Alejandra. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Rosenkranz, Peter. Universidad de Hohenheim; Alemani