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Beekeepers have various options to control the parasitic mite Varroa destructor in honey bee colonies, but no empirical data are available on the methods they apply in practice. We surveyed 28,409 beekeepers maintaining 507,641 colonies in 30 European countries concerning Varroa control methods. The set of 19 different Varroa diagnosis and control measures was taken from the annual COLOSS questionnaire on honey bee colony losses. The most frequent activities were monitoring of Varroa infestations, drone brood removal, various oxalic acid applications and formic acid applications. Correspondence analysis and hierarchical clustering on principal components showed that six Varroa control options (not necessarily the most used ones) significantly contribute to defining three distinctive clusters of countries in terms of Varroa control in Europe. Cluster I (eight Western European countries) is characterized by use of amitraz strips. Cluster II comprises 15 countries from Scandinavia, the Baltics, and Central-Southern Europe. This cluster is characterized by long-term formic acid treatments. Cluster III is characterized by dominant usage of amitraz fumigation and formed by seven Eastern European countries. The median number of different treatments applied per beekeeper was lowest in cluster III. Based on estimation of colony numbers in included countries, we extrapolated the proportions of colonies treated with different methods in Europe. This suggests that circa 62% of colonies in Europe are treated with amitraz, followed by oxalic acid for the next largest percentage of colonies. We discuss possible factors determining the choice of Varroa control measures in the different clusters.

Table S1. Utilized packages of the statistical software R version 4.0.4.

Pollen stored by bees undergoes a fermentation marked by the presence of lactic acid bacteria and yeasts. It results in bee bread. Past studies have singled out Starmerella (Candida) magnoliae as the most common yeast species in honey bee-stored bee bread. Starmerella species are ecological specialists with potential biotechnological value. The rarity of recent studies on yeasts in honey bees prompted us to generate new information on yeast diversity during the conversion of bee-collected pollen to bee bread. Bees and stored pollen from two apiaries in Belgium were sampled, a yeast isolation protocol was developed, yeast isolates were grouped according to their macroand micromorphology, and representative isolates were identified using DNA sequences. Most of the 252 identified isolates belonged to the genera Starmerella, Metschnikowia, and Zygosaccharomyces. The high abundance of yeasts in fresh bee bread decreased rapidly with the storage duration. Starmerella species dominated fresh bee bread, while mostly Zygosaccharomyces members were isolated from aged bee bread. Starmerella (Candida) apis, a rarely isolated species, was the most frequent and abundant species in fresh bee bread. Yeasts from the bee’s honey stomach and from pollen pellets obtained from bees hind legs were dominated by Metschnikowia species. The distinctive communities from pollen pellets over fresh bee bread to aged bee bread indicate a non-random distribution of these yeasts.

In this short note we present comparable loss rates of honey bee colonies during winter 2016/2017 from 27 European countries plus Algeria, Israel and Mexico, obtained with the COLOSS questionnaire. The 14,813 beekeepers providing valid loss data collectively wintered 425,762 colonies, and reported 21,887 (5.1%, 95% confidence interval 5.0-5.3%) colonies with unsolvable queen problems and 60,227 (14.1%, 95% CI 13.8-14.4%) dead colonies after winter. Additionally we asked for colonies lost due to natural disaster, which made up another 6,903 colonies (1.6%, 95% CI 1.5-1.7%). This results in an overall loss rate of 20.9% (95% CI 20.6-21.3%) of honey bee colonies during winter 2016/2017, with marked differences among countries. The overall analysis showed that small operations suffered higher losses than larger ones (p < 0.001). Overall migratory beekeeping had no significant effect on the risk of winter loss, though there was an effect in several countries. A table is presented giving detailed results from 30 countries. A map is also included, showing relative risk of colony winter loss at regional level.

For several decades now, an increasing phenomenon of enhanced honey bee colony mortality and morbidity is troubling beekeepers and naturalists. Such negative trends affect also wild pollinators and cast doubt about the sustainability of pollination both of wild plants and crops. These trends are also experienced in Belgium, country showing a level of annual colony losses above 18% in the best years. In addition, Walloon beekeepers describe for many years unspecific symptoms with their colonies like weaken colonies, queen losses, abnormal brood development or full death of the colony without any symptoms of disease. The aim of my work was to bring light in this situation, which revealed unexpected results. A prevalence case study carried out in the region of Wallonia by myself in collaboration with colleagues of the CRA-Wallonia, pointed at fungicides as the stressing factor linked to honey bee colony disorders. These pesticides considered harmless to bees, we started digging to understand the underlying reasons of our field observations. First we considered if they were just markers of intensive agriculture, not really having any toxicological effects on bees. Indeed, we found that colonies surrounded by conventionally-farmed crops were more likely to be contaminated by pesticides, in special fungicides. In addition, the colonies in these crop areas were more prone to show disorders. We also found that this contamination does not necessarily come from treated crops, but from wild plants or catch/cover crops in the surroundings or succeeding treated crops within a surface of at least 3 km radius. Then, I tested the direct toxicological effects fungicides on different colony individuals. I started by evaluating the effect of the most frequently found fungicide, boscalid, on be larvae, which did not show to induce increased mortality of immature bee stages. Then I studied the impact of chronic exposure of adult bees. Finally I suggest further research lines to better u, (AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 2017

We assessed the state of knowledge regarding the effects of large-scale pollution with neonicotinoid insecticides and fipronil on non-target invertebrate species of terrestrial, freshwater and marine environments. A large section of the assessment is dedicated to the state of knowledge on sublethal effects on honeybees (Apis mellifera) because this important pollinator is the most studied non-target invertebrate species. Lepidoptera (butterflies and moths), Lumbricidae (earthworms), Apoidae sensu lato (bumblebees, solitary bees) and the section “other invertebrates” review available studies on the other terrestrial species. The sections on freshwater and marine species are rather short as little is known so far about the impact of neonicotinoid insecticides and fipronil on the diverse invertebrate fauna of these widely exposed habitats. For terrestrial and aquatic invertebrate species, the known effects of neonicotinoid pesticides and fipronil are described ranging from organismal toxicology and behavioural effects to population-level effects. For earthworms, freshwater and marine species, the relation of findings to regulatory risk assessment is described. Neonicotinoid insecticides exhibit very high toxicity to a wide range of invertebrates, particularly insects, and field-realistic exposure is likely to result in both lethal and a broad range of important sublethal impacts. There is a major knowledge gap regarding impacts on the grand majority of invertebrates, many of which perform essential roles enabling healthy ecosystem functioning. The data on the few non-target species on which field tests have been performed are limited by major flaws in the outdated test protocols. Despite large knowledge gaps and uncertainties, enough knowledge exists to conclude that existing levels of pollution with neonicotinoids and fipronil resulting from presently authorized uses frequently exceed the lowest observed adverse effect concentrations and are thus likely to have large

Background: An individual honeybee shows a complex behavioral structure. Each bee takes part in the collective behavioral set up that ensures bee colony survival and development. Contaminants are likely to have effects on individual bees’ behavior with consequences at the level of the whole colony. They also are likely to alter bees’ physiology, including lifespan, fertility or fecundity, leading to colony weakness or colony collapse. Results: Peer-reviewed scientific literature provides a wide range of methods used for testing honeybees’ behavioral or physiological parameters. Apart from alterations that may appear during the conduction of acute or chronic toxicity tests, specific tests could be conducted to complement the risk assessment in order to evaluate the impact of sublethal doses of contaminants on bees. Such tests can be developed both in laboratory conditions or as part of the semi-field and field tests that are currently required as higher tier tests of risk assessment schemes. Conclusion: The purpose of this work is to review some of these methods and discuss their relevance in the evaluation of pesticide active substances and/or products in view to propose their future inclusion in pesticides risk assessment to bees. Keywords: honey bee, sublethal effects, risk assessment

peer-reviewed, This short article presents loss rates of honey bee colonies over winter 2017/18 from 36 countries, including 33 in Europe, from data collected using the standardized COLOSS questionnaire. The 25,363 beekeepers supplying data passing consistency checks in total wintered 544,879 colonies, and reported 26,379 (4.8%, 95% CI 4.7–5.0%) colonies with unsolvable queen problems, 54,525 (10.0%, 95% CI 9.8–10.2%) dead colonies after winter and another 8,220 colonies (1.5%, 95% CI 1.4–1.6%) lost through natural disaster. This gave an overall loss rate of 16.4% (95% CI 16.1–16.6%) of honey bee colonies during winter 2017/18, but this varied greatly from 2.0 to 32.8% between countries. The included map shows relative risks of winter loss at regional level. The analysis using the total data-set confirmed findings from earlier surveys that smaller beekeeping operations with at most 50 colonies suffer significantly higher losses than larger operations (p<.001). Beekeepers migrating their colonies had significantly lower losses than those not migrating (p<.001), a different finding from previous research. Evaluation of six different forage sources as potential risk factors for colony loss indicated that intensive foraging on any of five of these plant sources (Orchards, Oilseed Rape, Maize, Heather and Autumn Forage Crops) was associated with significantly higher winter losses. This finding requires further study and explanation. A table is included giving detailed results of loss rates and the impact of the tested forage sources for each country and overall.